Efficient quasi-monoenergetic ion beams from laser-driven relativistic plasmas

PubMed Central

Palaniyappan, Sasi; Huang, Chengkun; Gautier, Donald C.; Hamilton, Christopher E.; Santiago, Miguel A.; Kreuzer, Christian; Sefkow, Adam B.; Shah, Rahul C.; Fernández, Juan C.

2015-01-01

Table-top laser–plasma ion accelerators have many exciting applications, many of which require ion beams with simultaneous narrow energy spread and high conversion efficiency. However, achieving these requirements has been elusive. Here we report the experimental demonstration of laser-driven ion beams with narrow energy spread and energies up to 18 MeV per nucleon and ∼5% conversion efficiency (that is 4 J out of 80-J laser). Using computer simulations we identify a self-organizing scheme that reduces the ion energy spread after the laser exits the plasma through persisting self-generated plasma electric (∼1012 V m−1) and magnetic (∼104 T) fields. These results contribute to the development of next generation compact accelerators suitable for many applications such as isochoric heating for ion-fast ignition and producing warm dense matter for basic science. PMID:26657147

Efficient quasi-monoenergetic ion beams from laser-driven relativistic plasmas

DOE PAGES

Palaniyappan, Sasi; Huang, Chengkun; Gautier, Donald C.; ...

2015-12-11

Here, table-top laser–plasma ion accelerators have many exciting applications, many of which require ion beams with simultaneous narrow energy spread and high conversion efficiency. However, achieving these requirements has been elusive. Here we report the experimental demonstration of laser-driven ion beams with narrow energy spread and energies up to 18 MeV per nucleon and ~5% conversion efficiency (that is 4 J out of 80-J laser). Using computer simulations we identify a self-organizing scheme that reduces the ion energy spread after the laser exits the plasma through persisting self-generated plasma electric (~10 12 V m –1) and magnetic (~10 4 T)more » fields. These results contribute to the development of next generation compact accelerators suitable for many applications such as isochoric heating for ion-fast ignition and producing warm dense matter for basic science.« less

Mode conversion efficiency to Laguerre-Gaussian OAM modes using spiral phase optics.

PubMed

Longman, Andrew; Fedosejevs, Robert

2017-07-24

An analytical model for the conversion efficiency from a TEM 00 mode to an arbitrary Laguerre-Gaussian (LG) mode with null radial index spiral phase optics is presented. We extend this model to include the effects of stepped spiral phase optics, spiral phase optics of non-integer topological charge, and the reduction in conversion efficiency due to broad laser bandwidth. We find that through optimization, an optimal beam waist ratio of the input and output modes exists and is dependent upon the output azimuthal mode number.

Thermal neutron detector based on COTS CMOS imagers and a conversion layer containing Gadolinium

NASA Astrophysics Data System (ADS)

Pérez, Martín; Blostein, Juan Jerónimo; Bessia, Fabricio Alcalde; Tartaglione, Aureliano; Sidelnik, Iván; Haro, Miguel Sofo; Suárez, Sergio; Gimenez, Melisa Lucía; Berisso, Mariano Gómez; Lipovetzky, Jose

2018-06-01

In this work we will introduce a novel low cost position sensitive thermal neutron detection technique, based on a Commercial Off The Shelf CMOS image sensor covered with a Gadolinium containing conversion layer. The feasibility of the neutron detection technique implemented in this work has been experimentally demonstrated. A thermal neutron detection efficiency of 11.3% has been experimentally obtained with a conversion layer of 11.6 μm. It was experimentally verified that the thermal neutron detection efficiency of this technique is independent on the intensity of the incident thermal neutron flux, which was confirmed for conversion layers of different thicknesses. Based on the experimental results, a spatial resolution better than 25 μm is expected. This spatial resolution makes the proposed technique specially useful for neutron beam characterization, neutron beam dosimetry, high resolution neutron imaging, and several neutron scattering techniques.

Parametric Raman anti-Stokes laser at 503 nm with phase-matched collinear beam interaction of orthogonally polarized Raman components in calcite under 532 nm 20 ps laser pumping

NASA Astrophysics Data System (ADS)

Smetanin, Sergei; Jelínek, Michal; Kubeček, Václav

2017-05-01

Lasers based on stimulated-Raman-scattering process can be used for the frequency-conversion to the wavelengths that are not readily available from solid-state lasers. Parametric Raman lasers allow generation of not only Stokes, but also anti-Stokes components. However, practically all the known crystalline parametric Raman anti-Stokes lasers have very low conversion efficiencies of about 1 % at theoretically predicted values of up to 40 % because of relatively narrow angular tolerance of phase matching in comparison with angular divergence of the interacting beams. In our investigation, to widen the angular tolerance of four-wave mixing and to obtain high conversion efficiency into the antiStokes wave we propose and study a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phasematched collinear beam interaction of orthogonally polarized Raman components in calcite under 532 nm 20 ps laser pumping. We use only one 532-nm laser source to pump the Raman-active calcite crystal oriented at the phase matched angle for orthogonally polarized Raman components four-wave mixing. Additionally, we split the 532-nm laser radiation into the orthogonally polarized components entering to the Raman-active calcite crystal at the certain incidence angles to fulfill the tangential phase matching compensating walk-off of extraordinary waves for collinear beam interaction in the crystal with the widest angular tolerance of four-wave mixing. For the first time the highest 503-nm anti-Stokes conversion efficiency of 30 % close to the theoretical limit of about 40 % at overall optical efficiency of the parametric Raman anti-Stokes generation of up to 3.5 % in calcite is obtained due to realization of tangential phase matching insensitive to the angular mismatch.

CW 50W/M2 = 10.9 diode laser source by spectral beam combining based on a transmission grating.

PubMed

Zhang, Jun; Peng, Hangyu; Fu, Xihong; Liu, Yun; Qin, Li; Miao, Guoqing; Wang, Lijun

2013-02-11

An external cavity structure based on the -1st transmission grating is introduced to spectral beam combining a 970 nm diode laser bar. A CW output power of 50.8 W, an electro-optical conversion efficiency of 45%, a spectral beam combining efficiency of 90.2% and a holistic M(2) value of 10.9 are achieved. This shows a way for a diode laser source with several KW power and diffraction-limited beam quality at the same time.

Vector mode conversion based on tilted fiber Bragg grating in ring-core fibers

NASA Astrophysics Data System (ADS)

Mi, Yuean; Ren, Guobin; Gao, Yixiao; Li, Haisu; Zhu, Bofeng; Liu, Yu

2018-03-01

We propose a vector mode conversion approach based on tilted fiber Bragg grating (TFBG) written in ring-core fiber with effective separation of eigenmodes. The mode coupling properties of TFBG are numerically investigated. It is shown that under the constraint of phase matching, the conversion of high-order vector modes could be achieved at specific wavelengths. Moreover, the polarization of incident light and tilt angle of TFBG play critical roles in mode coupling process. The proposed TFBG provides an efficient method to realize high-order vector mode conversion, and it shows great potential for fibers based OAM beam generation and fiber lasers with vortex beams output.

Engineering of beam direct conversion for a 120-kV, 1-MW ion beam

NASA Technical Reports Server (NTRS)

Barr, W. L.; Doggett, J. N.; Hamilton, G. W.; Kinney, J. D.; Moir, R. W.

1977-01-01

Practical systems for beam direct conversion are required to recover the energy from ion beams at high efficiency and at very high beam power densities in the environment of a high-power neutral-injection system. Such an experiment is now in progress using a 120-kV beam with a maximum total current of 20 A. After neutralization, the H(+) component to be recovered will have a power of approximately 1 MW. A system testing these concepts has been designed and tested at 15 kV, 2 kW in preparation for the full-power tests. The engineering problems involved in the full-power tests affect electron suppression, gas pumping, voltage holding, diagnostics, and measurement conditions. Planning for future experiments at higher power includes the use of cryopumping and electron suppression by a magnetic field rather than by an electrostatic field. Beam direct conversion for large fusion experiments and reactors will save millions of dollars in the cost of power supplies and electricity and will dispose of the charged beam under conditions that may not be possible by other techniques.

Free electron lasers for transmission of energy in space

NASA Technical Reports Server (NTRS)

Segall, S. B.; Hiddleston, H. R.; Catella, G. C.

1981-01-01

A one-dimensional resonant-particle model of a free electron laser (FEL) is used to calculate laser gain and conversion efficiency of electron energy to photon energy. The optical beam profile for a resonant optical cavity is included in the model as an axial variation of laser intensity. The electron beam profile is matched to the optical beam profile and modeled as an axial variation of current density. Effective energy spread due to beam emittance is included. Accelerators appropriate for a space-based FEL oscillator are reviewed. Constraints on the concentric optical resonator and on systems required for space operation are described. An example is given of a space-based FEL that would produce 1.7 MW of average output power at 0.5 micrometer wavelength with over 50% conversion efficiency of electrical energy to laser energy. It would utilize a 10 m-long amplifier centered in a 200 m-long optical cavity. A 3-amp, 65 meV electrostatic accelerator would provide the electron beam and recover the beam after it passes through the amplifier. Three to five shuttle flights would be needed to place the laser in orbit.

High efficiency and high-energy intra-cavity beam shaping laser

NASA Astrophysics Data System (ADS)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-09-01

We present a technology of intra-cavity laser beam shaping with theory and experiment to obtain a flat-top-like beam with high-pulse energy. A radial birefringent element (RBE) was used in a crossed Porro prism polarization output coupling resonator to modulate the phase delay radially. The reflectively of a polarizer used as an output mirror was variable radially. A flat-top-like beam with 72.5 mJ, 11 ns at 20 Hz was achieved by a side-pumped Nd:YAG zigzag slab laser, and the optical-to-optical conversion efficiency was 17.3%.

High Efficiency Energy Extraction from a Relativistic Electron Beam in a Strongly Tapered Undulator

DOE PAGES

Sudar, N.; Musumeci, P.; Duris, J.; ...

2016-10-19

Here we present results of an experiment where, using a 200 GW CO 2 laser seed, a 65 MeV electron beam was decelerated down to 35 MeV in a 54-cm-long strongly tapered helical magnetic undulator, extracting over 30% of the initial electron beam energy to coherent radiation. These results, supported by simulations of the radiation field evolution, demonstrate unparalleled electro-optical conversion efficiencies for a relativistic beam in an undulator field and represent an important step in the development of high peak and average power coherent radiation sources.

Radiated microwave power transmission system efficiency measurements

NASA Technical Reports Server (NTRS)

Dickinson, R. M.; Brown, W. C.

1975-01-01

The measured and calculated results from determining the operating efficiencies of a laboratory version of a system for transporting electric power from one point to another via a wireless free space radiated microwave beam are reported. The system's overall end-to-end efficiency as well as intermediated conversion efficiencies were measured. The maximum achieved end-to-end dc-to-ac system efficiency was 54.18% with a probable error of + or - 0.94%. The dc-to-RF conversion efficiency was measured to be 68.87% + or - 1.0% and the RF-to-dc conversion efficiency was 78.67 + or - 1.1%. Under these conditions a dc power of 495.62 + or - 3.57 W was received with a free space transmitter antenna receiver antenna separation of 170.2 cm (67 in).

Free-space microwave power transmission study, phase 3

NASA Technical Reports Server (NTRS)

Brown, W. C.

1975-01-01

The results of an investigation of the technology of free-space power transmission by microwave beam are presented. A description of the steps that were taken to increase the overall dc to dc efficiency of microwave power transmission from 15 percent to over 50 percent is given. Included in this overall efficiency were the efficiencies of the dc to microwave conversion, the microwave transmission itself, and the microwave to dc conversion. Improvements in launching the microwave beam with high efficiency by means of a dual mode horn resulted in 95 percent of the output of the microwave generator reaching the receiving area. Emphasis was placed upon successive improvements in reception and rectification of the microwave power, resulting in the design of a rectenna device for this purpose whose efficiency was 75 percent. The procedures and the hardware developed were the basis for tests certified by the Jet Propulsion Laboratory in which an overall dc to dc efficiency of 54 percent was achieved.

Efficient frequency conversion by stimulated Raman scattering in a sodium nitrate aqueous solution

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

Ganot, Yuval, E-mail: yuvalga@sapir.ac.il, E-mail: ibar@bgu.ac.il; Bar, Ilana, E-mail: yuvalga@sapir.ac.il, E-mail: ibar@bgu.ac.il

2015-09-28

Frequency conversion of laser beams, based on stimulated Raman scattering (SRS) is an appealing technique for generating radiation at new wavelengths. Here, we investigated experimentally the SRS due to a single pass of a collimated frequency-doubled Nd:YAG laser beam (532 nm) through a saturated aqueous solution of sodium nitrate (NaNO{sub 3}), filling a 50 cm long cell. These experiments resulted in simultaneous generation of 1st (564 nm) and 2nd (599 nm) Stokes beams, corresponding to the symmetric stretching mode of the nitrate ion, ν{sub 1}(NO{sub 3}{sup −}), with 40 and 12 mJ/pulse maximal converted energies, equivalent to 12% and 4% efficiencies, respectively, for a 340more » mJ/pulse pump energy. The results indicate that the pump and SRS beams were thermally defocused and that four-wave mixing was responsible for the second order Stokes process onset.« less

Improvement of force factor of magnetostrictive vibration power generator for high efficiency

NASA Astrophysics Data System (ADS)

Kita, Shota; Ueno, Toshiyuki; Yamada, Sotoshi

2015-05-01

We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.

Gyroharmonic conversion experiments

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

Hirshfield, J. L.; LaPointe, M. A.; Yale University, New Haven, Connecticut 06511

1999-05-07

Generation of high power microwaves has been observed in experiments where a 250-350 kV, 20-30 A electron beam accelerated in a cyclotron autoresonance accelerator (CARA) passes through a cavity tuned gyroharmonic) and at 8.6 GHz (3rd harmonic) will be described. Theory indicates that high conversion efficiency can be obtained for a high quality beam injected into CARA, and when mode competition can be controlled. Comparisons will be made between the experiments and theory. Planned 7th harmonic experiments will also be described, in which phase matching between the TE-72 mode at 20 GHz, and the TE-11 mode at 2.86 GHz, allowsmore » efficient 20 GHz co-generation within the CARA waveguide itself.« less

Theoretical explanation of the polarization-converting system achieved by beam shaping and combination technique and its performance under high power conditions

NASA Astrophysics Data System (ADS)

Wang, Peng; Li, Xiao; Shang, YaPing; Xu, XiaoJun

2015-10-01

The fiber laser has very obvious advantages and broad applications in remote welding, 3D cutting and national defense compared with the traditional solid laser. But influenced by heat effect of gain medium, nonlinear effect, stress birefringence effect and other negative factors, it's very difficult to get high power linearly polarized laser just using a single laser. For these limitations a polarization-converting system is designed using beam shaping and combination technique which is able to transform naturally polarized laser to linearly polarized laser at real time to resolve difficulties of generating high-power linearly polarized laser from fiber lasers in this paper. The principle of the Gaussian beam changing into the hollow beam passing through two axicons and the combination of the Gaussian beam and the hollow beam is discussed. In the experimental verification the energy conversion efficiency reached 93.1% with a remarkable enhancement of the extinction ratio from 3% to 98% benefited from the high conversion efficiency of axicons and the system worked fine under high power conditions. The system also kept excellent far field divergence. The experiment phenomenon also agreed with the simulation quite well. The experiment proves that this polarization-converting system will not affect laser structure which controls easily and needs no feedback and controlling system with stable and reliable properties at the same time. It can absolutely be applied to the polarization-conversion of high power laser.

Selective deuterium ion acceleration using the Vulcan petawatt laser

NASA Astrophysics Data System (ADS)

Krygier, A. G.; Morrison, J. T.; Kar, S.; Ahmed, H.; Alejo, A.; Clarke, R.; Fuchs, J.; Green, A.; Jung, D.; Kleinschmidt, A.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Notley, M.; Oliver, M.; Roth, M.; Vassura, L.; Zepf, M.; Borghesi, M.; Freeman, R. R.

2015-05-01

We report on the successful demonstration of selective acceleration of deuterium ions by target-normal sheath acceleration (TNSA) with a high-energy petawatt laser. TNSA typically produces a multi-species ion beam that originates from the intrinsic hydrocarbon and water vapor contaminants on the target surface. Using the method first developed by Morrison et al. [Phys. Plasmas 19, 030707 (2012)], an ion beam with >99% deuterium ions and peak energy 14 MeV/nucleon is produced with a 200 J, 700 fs, > 10 20 W / cm 2 laser pulse by cryogenically freezing heavy water (D2O) vapor onto the rear surface of the target prior to the shot. Within the range of our detectors (0°-8.5°), we find laser-to-deuterium-ion energy conversion efficiency of 4.3% above 0.7 MeV/nucleon while a conservative estimate of the total beam gives a conversion efficiency of 9.4%.

Two and Three Beam Pumped Optical Parametric Amplifier of Chirped Pulses

NASA Astrophysics Data System (ADS)

Ališauskas, S.; Butkus, R.; Pyragaitė, V.; Smilgevičius, V.; Stabinis, A.; Piskarskas, A.

2010-04-01

We present two and three beam pumped optical parametric amplifier of broadband chirped pulses. The seed pulses from Ti:sapphire oscillator were stretched and amplified in a non-collinear geometry pumping with up to three beams derived from independent laser amplifiers. The signal with ˜90 nm bandwidth was amplified up to 0.72 mJ. The conversion efficiency dependence on intersection angles of pump beams is also revealed.

Adaptive conversion of a high-order mode beam into a near-diffraction-limited beam.

PubMed

Zhao, Haichuan; Wang, Xiaolin; Ma, Haotong; Zhou, Pu; Ma, Yanxing; Xu, Xiaojun; Zhao, Yijun

2011-08-01

We present a new method for efficiently transforming a high-order mode beam into a nearly Gaussian beam with much higher beam quality. The method is based on modulation of phases of different lobes by stochastic parallel gradient descent algorithm and coherent addition after phase flattening. We demonstrate the method by transforming an LP11 mode into a nearly Gaussian beam. The experimental results reveal that the power in the diffraction-limited bucket in the far field is increased by more than a factor of 1.5.

Improved foilless Ku-band transit-time oscillator for generating gigawatt level microwave with low guiding magnetic field

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

Ling, Junpu; He, Juntao, E-mail: hejuntao12@163.com; Zhang, Jiande

2014-09-15

An improved foilless Ku-band transit-time oscillator with low guiding magnetic field is proposed and investigated in this paper. With a non-uniform buncher and a coaxial TM{sub 02} mode dual-resonant reflector, this improved device can output gigawatt level Ku-band microwave with relatively compact radial dimensions. Besides the above virtue, this novel reflector also has the merits of high TEM reflectance, being more suitable for pre-modulating the electron beam and enhancing the conversion efficiency. Moreover, in order to further increase the conversion efficiency and lower the power saturation time, a depth-tunable coaxial collector and a resonant cavity located before the extractor aremore » employed in our device. Main structure parameters of the device are optimized by particle in cell simulations. The typical simulation result is that, with a 380 kV, 8.2 kA beam guided by a magnetic field of about 0.6 T, 1.15 GW microwave pulse at 14.25 GHz is generated, yielding a conversion efficiency of about 37%.« less

Fully Controllable Pancharatnam-Berry Metasurface Array with High Conversion Efficiency and Broad Bandwidth

PubMed Central

Liu, Chuanbao; Bai, Yang; Zhao, Qian; Yang, Yihao; Chen, Hongsheng; Zhou, Ji; Qiao, Lijie

2016-01-01

Metasurfaces have powerful abilities to manipulate the properties of electromagnetic waves flexibly, especially the modulation of polarization state for both linearly polarized (LP) and circularly polarized (CP) waves. However, the transmission efficiency of cross-polarization conversion by a single-layer metasurface has a low theoretical upper limit of 25% and the bandwidth is usually narrow, which cannot be resolved by their simple additions. Here, we efficiently manipulate polarization coupling in multilayer metasurface to promote the transmission of cross-polarization by Fabry-Perot resonance, so that a high conversion coefficient of 80–90% of CP wave is achieved within a broad bandwidth in the metasurface with C-shaped scatters by theoretical calculation, numerical simulation and experiments. Further, fully controlling Pancharatnam-Berry phase enables to realize polarized beam splitter, which is demonstrated to produce abnormal transmission with high conversion efficiency and broad bandwidth. PMID:27703254

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler.

PubMed

Kardaś, Tomasz M; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-22

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler

NASA Astrophysics Data System (ADS)

Kardaś, Tomasz M.; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-01

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Thermal dephasing in second-harmonic generation of an amplified copper-vapor laser beam in beta barium borate.

PubMed

Prakash, Om; Dixit, Sudhir Kumar; Bhatnagar, Rajiva

2005-03-20

The conversion efficiency in second-harmonic generation of an amplified beam in a master-oscillator power amplifier copper-vapor laser (CVL) is lower than that of the oscillator beam alone. This lower efficiency is often vaguely attributed to wave-front degradation in the amplifier. We investigate the role of wave-front degradation and thermal dephasing in the second-harmonic generation of a CVL from a beta-barium borate crystal. Choosing two beams with constant intrapulse divergence, one from a generalized diffraction filtered resonator master oscillator alone and other obtained by amplifying oscillator by use of a power amplifier, we show that at low flux levels the decrease in efficiency is due to wave-front degradation. At a fundamental power above the critical power for thermal dephasing, the decrease is due to increased UV absorption and consequent thermal dephasing. Thermal dephasing is higher for the beam with the lower coherence width.

LP01 to LP11 mode convertor based on side-polished small-core single-mode fiber

NASA Astrophysics Data System (ADS)

Liu, Yan; Li, Yang; Li, Wei-dong

2018-03-01

An all-fiber LP01-LP11 mode convertor based on side-polished small-core single-mode fibers (SMFs) is numerically demonstrated. The linearly polarized incident beam in one arm experiences π shift through a fiber half waveplate, and the side-polished parts merge into an equivalent twin-core fiber (TCF) which spatially shapes the incident LP01 modes to the LP11 mode supported by the step-index few-mode fiber (FMF). Optimum conditions for the highest conversion efficiency are investigated using the beam propagation method (BPM) with an approximate efficiency as high as 96.7%. The proposed scheme can operate within a wide wavelength range from 1.3 μm to1.7 μm with overall conversion efficiency greater than 95%. The effective mode area and coupling loss are also characterized in detail by finite element method (FEM).

A simulation study on the mode conversion process from slow Z-mode to LO mode by the tunneling effect and variations of beaming angle

NASA Astrophysics Data System (ADS)

Kalaee, Mohammad Javad; Katoh, Yuto

2014-12-01

For a particular angle of incidence wave, it is possible for a slow Z-mode wave incident on an inhomogeneous plasma slab to be converted into an LO mode wave. But for another wave normal angle of the incident wave, it has been considered impossible, since an evanescence region exists between two mode branches. In this case we expect that the mode conversion takes place through the tunneling effect. We investigate the effect of the spatial scale of the density gradient on the mode conversion efficiency in an inhomogeneous plasma where the mode conversion can occur only by the tunneling effect. We use the computer simulation solving Maxwell's equations and the motion of a cold electron fluid. By considering the steepness of the density gradient, the simulation results show the efficient mode conversion could be expected even in the case that the mismatch of the refractive indexes prevents the close coupling of plasma waves. Also, we show for these cases the beaming angle does not correspond to Jones' formula. This effect leads to the angles larger and smaller than the angle estimated by the formula. This type of mode conversion process becomes important in a case where the different plasmas form a discontinuity at their contact boundary.

Energy regeneration model of self-consistent field of electron beams into electric power*

NASA Astrophysics Data System (ADS)

Kazmin, B. N.; Ryzhov, D. R.; Trifanov, I. V.; Snezhko, A. A.; Savelyeva, M. V.

2016-04-01

We consider physic-mathematical models of electric processes in electron beams, conversion of beam parameters into electric power values and their transformation into users’ electric power grid (onboard spacecraft network). We perform computer simulation validating high energy efficiency of the studied processes to be applied in the electric power technology to produce the power as well as electric power plants and propulsion installation in the spacecraft.

35 GHz integrated circuit rectifying antenna with 33 percent efficiency

NASA Technical Reports Server (NTRS)

Yoo, T.-W.; Chang, K.

1991-01-01

A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33 percent conversion efficiency has been achieved. The circuit should have applications in microwave/millimeter-wave power transmission and detection.

Gyroharmonic conversion experiments

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

Hirshfield, J.L.; LaPointe, M.A.; Ganguly, A.K.

1999-05-01

Generation of high power microwaves has been observed in experiments where a 250{endash}350 kV, 20{endash}30 A electron beam accelerated in a cyclotron autoresonance accelerator (CARA) passes through a cavity tuned gyroharmonic) and at 8.6 GHz (3rd harmonic) will be described. Theory indicates that high conversion efficiency can be obtained for a high quality beam injected into CARA, and when mode competition can be controlled. Comparisons will be made between the experiments and theory. Planned 7th harmonic experiments will also be described, in which phase matching between the TE-72 mode at 20 GHz, and the TE-11 mode at 2.86 GHz, allowsmore » efficient 20 GHz co-generation within the CARA waveguide itself. {copyright} {ital 1999 American Institute of Physics.}« less

Diode-side-pumped continuous wave Nd³⁺ : YVO₄ self-Raman laser at 1176 nm.

PubMed

Kores, Cristine Calil; Jakutis-Neto, Jonas; Geskus, Dimitri; Pask, Helen M; Wetter, Niklaus U

2015-08-01

Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd3+:YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd3+:YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.

Measuring parameters of large-aperture crystals used for generating optical harmonics

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

English, R. E.; Hibbard, R. L.; Michie, R. B.

1999-02-23

The purpose of this project was to develop tools for understanding the influence of crystal quality and crystal mounting on harmonic-generation efficiency at high irradiance. Measuring the homogeneity of crystals interferometrically, making detailed physics calculations of conversion efficiency, performing finite- element modeling of mounted crystals, and designing a new optical metrology tool were key elements in obtaining that understanding. For this work, we used the following frequency-tripling scheme: type I second- harmonic generation followed by type II sum-frequency mixing of the residual fundamental and the second harmonic light. The doubler was potassium dihydrogen phosphate (KDP), and the tripler was deuteratedmore » KDP (KD*P). With this scheme, near-infrared light (1053 nm) can be frequency tripled (to 351 nm) at high efficiency (theoretically >90%) for high irradiance (>3 GW/cm²). Spatial variations in the birefringence of the large crystals studied here (37 to 41 cm square by about 1 cm thick) imply that the ideal phase-matching orientation of the crystal with respect to the incident laser beam varies across the crystal. We have shown that phase-measuring interferometry can be used to measure these spatial variations. We observed transmitted wavefront differences between orthogonally polarized interferograms of {lambda}/50 to {lambda}/100, which correspond to index variations of order 10 -6. On some plates that we measured, the standard deviation of angular errors is 22-23 µrad; this corresponds to a 1% reduction in efficiency. Because these conversion crystals are relatively thin, their surfaces are not flat (deviate by k2.5 urn from flat). A crystal is mounted against a precision-machined surface that supports the crystal on four edges. This mounting surface is not flat either (deviates by +2.5 µm from flat). A retaining flange presses a compliant element against the crystal. The load thus applied near the edges of the crystal surface holds it in place. We performed detailed finite-element modeling to predict the resulting shape of the mounted crystal. The prediction agreed with measurements of mounted crystals. We computed the physics of the frequency-conversion process to better quantify the effects on efficiency of variation in the crystal' s axis, changes in the shape of the crystal, and mounting-induced stress. We were able to accurately predict the frequency-conversion performance of 37-cm square crystals on Beamlet, a one-beam scientific prototype of the NIF laser architecture, using interferometric measurements of the mounted crystals and the model. In a 2{omega} measurement campaign, the model predicted 64.9% conversion efficiency; 64.1% was observed. When detuned by 640 µrad, the model and measurement agreement is even better (both were 10.4%). Finally, we completed the design and initial testing of a new optical metrology tool to measure the spatial variation of frequency conversion. This system employs a high-power subaperture beam from a commercial laser oscillator and rod amplifier. The beam interrogates the crystal' s aperture by moving the crystal horizontally on a translation stage and translating the laser beam vertically on an optical periscope. Precision alignment is maintained by means of a full-aperture reference mirror, a precision-machined surface on the crystal mount, and autocollimators (the goal for angular errors is 10 µrad). The autocollimators track the mounting angle of the crystal and the direction of the laser beam with respect to the reference mirror. The conversion efficiency can be directly measured by recording l{omega}, 2{omega}, 3{omega} energy levels during the scan and by rocking (i.e., tilting) the crystal mount over an angular range.« less

Reconstructing a plasmonic metasurface for a broadband high-efficiency optical vortex in the visible frequency.

PubMed

Lu, Bing-Rui; Deng, Jianan; Li, Qi; Zhang, Sichao; Zhou, Jing; Zhou, Lei; Chen, Yifang

2018-06-14

Metasurfaces consisting of a two-dimensional metallic nano-antenna array are capable of transferring a Gaussian beam into an optical vortex with a helical phase front and a phase singularity by manipulating the polarization/phase status of light. This miniaturizes a laboratory scaled optical system into a wafer scale component, opening up a new area for broad applications in optics. However, the low conversion efficiency to generate a vortex beam from circularly polarized light hinders further development. This paper reports our recent success in improving the efficiency over a broad waveband at the visible frequency compared with the existing work. The choice of material, the geometry and the spatial organization of meta-atoms, and the fabrication fidelity are theoretically investigated by the Jones matrix method. The theoretical conversion efficiency over 40% in the visible wavelength range is worked out by systematic calculation using the finite difference time domain (FDTD) method. The fabricated metasurface based on the parameters by theoretical optimization demonstrates a high quality vortex in optical frequencies with a significantly enhanced efficiency of over 20% in a broad waveband.

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

Kita, Shota, E-mail: happiest3.7@gmail.com; Ueno, Toshiyuki; Yamada, Sotoshi

We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversionmore » efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.« less

Active Signal Propagation and Imaging Using Vortex Beams

DTIC Science & Technology

2014-08-01

Though this method of OV beam generation allows dynamic control it also results in poor power conversion efficiency (~< 15%) and relatively low power...rectangular quart cell (1cm x 10 cm x 10cm). Various TM conditions are simulated inside the cell by diluting deionized water with polystyrene spheres...c). Both beams were then focused into a 1cm x 1cm x 10cm glass cell comprising a solution of latex spheres and ionized water . Different particle

2000W high beam quality diode laser for direct materials processing

NASA Astrophysics Data System (ADS)

Qin, Wen-bin; Liu, You-qiang; Cao, Yin-hua; Gao, Jing; Pan, Fei; Wang, Zhi-yong

2011-11-01

This article describes high beam quality and kilowatt-class diode laser system for direct materials processing, using optical design software ZEMAX® to simulate the diode laser optical path, including the beam shaping, collimation, coupling, focus, etc.. In the experiment, the diode laser stack of 808nm and the diode laser stack of 915nm were used for the wavelength coupling, which were built vertical stacks up to 16 bars. The threshold current of the stack is 6.4A, the operating current is 85A and the output power is 1280W. Through experiments, after collimating the diode laser beam with micro-lenses, the fast axis BPP of the stack is less than 60mm.mrad, and the slow-axis BPP of the stack is less than 75mm.mrad. After shaping the laser beam and improving the beam quality, the fast axis BPP of the stack is still 60mm.mrad, and the slow-axis BPP of the stack is less than 19mm.mrad. After wavelength coupling and focusing, ultimately the power of 2150W was obtained, focal spot size of 1.5mm * 1.2mm with focal length 300mm. The laser power density is 1.2×105W/cm2, and that can be used for metal remelting, alloying, cladding and welding. The total optical coupling conversion efficiency is 84%, and the total electrical - optical conversion efficiency is 50%.

Direct measurement of optoacoustic induced ultrasonic waves

NASA Astrophysics Data System (ADS)

Kuo, C.-Y.; Patel, C. K. N.

1984-04-01

A two-beam optically induced photoacoustic grating and its low frequency ultrasonic waves are measured with a thin film transducer in low concentration dye solution. The acoustic power generated is measured for a weakly absorbing medium to be equal to about 5 W sq cm, indicating high conversion efficiency. Application of this direct detection as a laser beam profiler is also discussed.

Design, construction and evaluation of a 12.2 GHz, 4.0 kW-CW high efficiency klystron amplifier. [for satellite-borne TV broadcast transmitters

NASA Technical Reports Server (NTRS)

Vishida, J. M.; Brodersen, L. K.

1974-01-01

An analytical and experimental program is described, for studying design techniques for optimizing the conversion efficiency of klystron amplifiers, and to utilize these techniques in the development and fabrication of an X-band 4 kW cw klystron, for use in satellite-borne television broadcast transmitters. The design is based on a technique for increasing the RF beam current by using the second harmonic space charge forces in the bunched beam. Experimental analysis was also made of a method to enhance circuit efficiency in the klystron cavities. The design incorporates a collector which is demountable from the tube to facilitate multistage depressed collector experiments employing an axisymmetric, electrostatic collector for linear beam microwave tubes.

Plasma q -plate for generation and manipulation of intense optical vortices

NASA Astrophysics Data System (ADS)

Qu, Kenan; Jia, Qing; Fisch, Nathaniel J.

2017-11-01

An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here we propose the design of suitably magnetized plasmas which, functioning as a q -plate, leads to a direct conversion from a high-intensity Gaussian beam into a twisted beam. A circularly polarized laser beam in the plasma accumulates an azimuthal-angle-dependent phase shift and hence forms a twisting wavefront. Our three-dimensional particle-in-cell simulations demonstrate extremely high-power conversion efficiency. The plasma q -plate can work in a large range of frequencies spanning from terahertz to the optical domain.

Parametric Raman crystalline anti-Stokes laser at 503 nm with collinear beam interaction at tangential phase matching

NASA Astrophysics Data System (ADS)

Smetanin, S. N.; Jelínek, M.; Kubeček, V.

2017-07-01

Stimulated-Raman-scattering in crystals can be used for the single-pass frequency-conversion to the Stokes-shifted wavelengths. The anti-Stokes shift can also be achieved but the phase-matching condition has to be fulfilled because of the parametric four-wave mixing process. To widen the angular-tolerance of four-wave mixing and to obtain high-conversion-efficiency into the anti-Stokes, we developed a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phase-matched collinear beam interaction of orthogonally-polarized Raman components in calcite oriented at the phase-matched angle under 532 nm 20 ps laser excitation. The excitation laser beam was split into two orthogonally-polarized components entering the calcite at the certain incidence angles to fulfill the nearly collinear phase-matching and also to compensate walk-off of extraordinary waves for collinear beam interaction. The phase matching of parametric Raman interaction is tangential and insensitive to the angular mismatch if the Poynting vectors of the biharmonic pump and parametrically generated (anti-Stokes) waves are collinear. For the first time it allows to achieve experimentally the highest conversion efficiency into the anti-Stokes wave (503 nm) up to 30% from the probe wave and up to 3.5% from both pump and probe waves in the single-pass picosecond parametric calcite Raman laser. The highest anti-Stokes pulse energy was 1.4 μJ.

Spin-to-orbit conversion at acousto-optic diffraction of light: conservation of optical angular momentum.

PubMed

Skab, Ihor; Vlokh, Rostyslav

2012-04-01

Acousto-optic diffraction of light in optically active cubic crystals is analyzed from the viewpoint of conservation of optical angular momentum. It is shown that the availability of angular momentum in the diffracted optical beam can be necessarily inferred from the requirements of angular momentum conservation law. As follows from our analysis, a circularly polarized diffracted wave should bear an orbital angular momentum. The efficiency of the spin-to-orbit momentum conversion is governed by the efficiency of acousto-optic diffraction.

Thermoelectric Figures of Merit of Zn4Sb3 and Zrnisn-based Half-heusler Compounds Influenced by Mev Ion-beam Bombardments

NASA Astrophysics Data System (ADS)

Budak, S.; Guner, S.; Muntele, C. I.; Ila, D.

Semiconducting β-Zn4Sb3 and ZrNiSn-based half-Heusler compound thin films with applications as thermoelectric (TE) materials were prepared using ion beam assisted deposition (IBAD). High-purity solid zinc (Zn) and antimony (Sb) were evaporated by electron beam to grow the β-Zn4Sb3 thin film while high-purity zirconium (Zr) powder and nickel (Ni) tin (Sn) powders were evaporated by electron beam to grow the ZrNiSn-based half-Heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardment for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardment. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam couldcause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ω-method (3rd harmonic) measurement system to measure the cross-plane thermal conductivity, the van der Pauw measurement system to measure the electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.

Diffraction properties of opaque disks outside and inside a laser cavity

NASA Astrophysics Data System (ADS)

de Saint Denis, Renaud; Passilly, Nicolas; Fromager, Michael; Cagniot, Emmanuel; Ait-Ameur, Kamel

2008-02-01

Diffraction of symmetrical Laguerre-Gauss TEMp0 beams incident on an opaque disk known as a stop is considered. The near- and far-field patterns are studied. Thanks to zero-field occluding, conversion from TEM10 beam to dark hollow beam can be achieved with better efficiency than from a TEM00 beam. It is shown that the fundamental mode of a laser cavity including a diaphragm and a stop can be TEM00- or TEM10-like in shape depending on their size. This result is interpreted from the new divergence hierarchy, which characterises the diffracted TEMp0 beams emerging from the stop.

Scaling the spectral beam combining channel by multiple diode laser stacks in an external cavity

NASA Astrophysics Data System (ADS)

Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao; Lei, Fuchuan; Yu, Junhong; Tan, Hao

2017-04-01

Spectral beam combining of a broad area diode laser is a promising technique for direct diode laser applications. We present an experimental study of three mini-bar stacks in an external cavity on spectral beam combining in conjunction with spatial beam combining. At the pump current of 70 A, a CW output power of 579 W, spectral bandwidth of 18.8 nm and electro-optical conversion efficiency of 47% are achieved. The measured M 2 values of spectral beam combining are 18.4 and 14.7 for the fast and the slow axis, respectively. The brightness of the spectral beam combining output is 232 MW · cm-2 · sr-1.

On-chip coherent conversion of photonic quantum entanglement between different degrees of freedom

PubMed Central

Feng, Lan-Tian; Zhang, Ming; Zhou, Zhi-Yuan; Li, Ming; Xiong, Xiao; Yu, Le; Shi, Bao-Sen; Guo, Guo-Ping; Dai, Dao-Xin; Ren, Xi-Feng; Guo, Guang-Can

2016-01-01

In the quantum world, a single particle can have various degrees of freedom to encode quantum information. Controlling multiple degrees of freedom simultaneously is necessary to describe a particle fully and, therefore, to use it more efficiently. Here we introduce the transverse waveguide-mode degree of freedom to quantum photonic integrated circuits, and demonstrate the coherent conversion of a photonic quantum state between path, polarization and transverse waveguide-mode degrees of freedom on a single chip. The preservation of quantum coherence in these conversion processes is proven by single-photon and two-photon quantum interference using a fibre beam splitter or on-chip beam splitters. These results provide us with the ability to control and convert multiple degrees of freedom of photons for quantum photonic integrated circuit-based quantum information process. PMID:27321821

On-chip coherent conversion of photonic quantum entanglement between different degrees of freedom.

PubMed

Feng, Lan-Tian; Zhang, Ming; Zhou, Zhi-Yuan; Li, Ming; Xiong, Xiao; Yu, Le; Shi, Bao-Sen; Guo, Guo-Ping; Dai, Dao-Xin; Ren, Xi-Feng; Guo, Guang-Can

2016-06-20

In the quantum world, a single particle can have various degrees of freedom to encode quantum information. Controlling multiple degrees of freedom simultaneously is necessary to describe a particle fully and, therefore, to use it more efficiently. Here we introduce the transverse waveguide-mode degree of freedom to quantum photonic integrated circuits, and demonstrate the coherent conversion of a photonic quantum state between path, polarization and transverse waveguide-mode degrees of freedom on a single chip. The preservation of quantum coherence in these conversion processes is proven by single-photon and two-photon quantum interference using a fibre beam splitter or on-chip beam splitters. These results provide us with the ability to control and convert multiple degrees of freedom of photons for quantum photonic integrated circuit-based quantum information process.

Demonstrated Efficient Quasi-Monoenergetic Carbon-Ion Beams Approaching Fast Ignition (FI) Requirements

NASA Astrophysics Data System (ADS)

Fernández, Juan C.; Palaniyappan, S.; Huang, C.; Gautier, D. C.; Santiago, M.

2015-11-01

Using massive computer simulations of relativistic laser-plasma interactions, we have identified a self-organizing scheme that exploits persisting self-generated plasma electric (~TV/m) and magnetic (~104 Tesla) fields to reduce the ion energy spread of intense laser-driven ion beams after the laser exits the plasma. Consistent with the scheme, we have demonstrated on the LANL Trident laser carbon-ion beams with narrow spectral peaks at 220 MeV, with high conversion efficiency (~ 5%). These parameters are within a factor of 2 of FI requirements. The remaining gap may be bridged by increasing the laser intensity by a factor of 4, according to our data. We also discuss how this beam may be focused, to address the remaining requirement for FI, besides the total laser energy. This work is sponsored by the LANL LDRD Program.

Photovoltaic Properties of p-Doped GaAs Nanowire Arrays Grown on n-Type GaAs(111)B Substrate

PubMed Central

2010-01-01

We report on the molecular beam epitaxy growth of Au-assisted GaAs p-type-doped NW arrays on the n-type GaAs(111)B substrate and their photovoltaic properties. The samples are grown at different substrate temperature within the range from 520 to 580 °C. It is shown that the dependence of conversion efficiency on the substrate temperature has a maximum at the substrate temperature of 550 °C. For the best sample, the conversion efficiency of 1.65% and the fill factor of 25% are obtained. PMID:20672038

Efficient tight focusing of laser beams optimally matched to their thin-film linear-to-radial polarization conversion: Method, implementation, and field near focus

NASA Astrophysics Data System (ADS)

Sedukhin, Andrey G.; Poleshchuk, Alexander G.

2018-01-01

A method is proposed for efficient, rotationally symmetric, tight mirror focusing of laser beams that is optimally matched to their thin-film linear-to-radial polarization conversion by a constant near-Brewster angle of incidence of the beams onto a polarizing element. Two optical systems and their modifications are considered that are based on this method and on the use of Toraldo filters. If focusing components of these systems operate in media with refractive indices equal to that of the focal region, they take the form of an axicon and an annular reflector generated by the revolution of an inclined parabola around the optical axis. Vectorial formulas for calculating the diffracted field near the focus of these systems are derived. Also presented are the results of designing a thin-film obliquely illuminated polarizer and a numerical simulation of deep UV laser beams generated by one of the systems and focused in an immersion liquid. The transverse and axial sizes of a needle longitudinally polarized field generated by the system with a simplest phase Toraldo filter were found to be 0.39 λ and 10.5 λ, with λ being the wavelength in the immersion liquid.

Relativistic twistron based on backward-wave oscillator with modulating reflector and an efficiency of 56%

NASA Astrophysics Data System (ADS)

Totmeninov, E. M.; Pegel, I. V.; Tarakanov, V. P.

2017-06-01

Using numerical simulation, the operating mode of a relativistic Cherenkov microwave generator of the twistronic type has been demonstrated. The generator includes an electrodynamic system based on a backward-wave oscillator and modulating reflector with nonmonotonous, highly nonuniform energy exchange along the length of the system. The efficiency of power conversion from the electron beam to electromagnetic radiation is 56%, and the electronic efficiency is 66%. For an accelerating voltage of 340 kV and an electron beam current of 3.3 kA, the simulated generation power is 630 MW at a frequency of 9.7 GHz and a guiding magnetic field of 2.2 T.

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

PubMed

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

2017-01-23

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

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

PubMed Central

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

2017-01-01

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

Multi-Wavelength, Multi-Beam, and Polarization-Sensitive Laser Transmitter for Surface Mapping

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Ramos-Izquierdo, Luis; Harding, David; Huss, Tim

2011-01-01

A multi-beam, multi-color, polarized laser transmitter has been developed for mapping applications. It uses commercial off-the-shelf components for a lowcost approach for a ruggedized laser suitable for field deployment. The laser transmitter design is capable of delivering dual wavelengths, multiple beams on each wavelength with equal (or variable) intensities per beam, and a welldefined state of polarization. This laser transmitter has been flown on several airborne campaigns for the Slope Imaging Multi-Polarization Photon Counting Lidar (SIMPL) instrument, and at the time of this reporting is at a technology readiness level of between 5 and 6. The laser is a 1,064-nm microchip high-repetition-rate laser emitting energy of about 8 microjoules per pulse. The beam was frequency-doubled to 532 nm using a KTP (KTiOPO4) nonlinear crystal [other nonlinear crystals such as LBO (LiB3O5) or periodically poled lithium niobiate can be used as well, depending on the conversion efficiency requirements], and the conversion efficiency was approximately 30 percent. The KTP was under temperature control using a thermoelectric cooler and a feedback monitoring thermistor. The dual-wavelength beams were then spectrally separated and each color went through its own optical path, which consisted of a beam-shaping lens, quarterwave plate (QWP), and a birefringent crystal (in this case, a calcite crystal, but others such as vanadate can be used). The QWP and calcite crystal set was used to convert the laser beams from a linearly polarized state to circularly polarized light, which when injected into a calcite crystal, will spatially separate the circularly polarized light into the two linear polarized components. The spatial separation of the two linearly polarized components is determined by the length of the crystal. A second set of QWP and calcite then further separated the two beams into four. Additional sets of QWP and calcite can be used to further split the beams into multiple orders of two. The spatially separated beams had alternating linearly polarization states; a half-wave plate (HWP) array was then made to rotate the alternating states of A multi-beam, multi-color, polarized laser transmitter has been developed for mapping applications. It uses commercial off-the-shelf components for a lowcost approach for a ruggedized laser suitable for field deployment. The laser transmitter design is capable of delivering dual wavelengths, multiple beams on each wavelength with equal (or variable) intensities per beam, and a welldefined state of polarization. This laser transmitter has been flown on several airborne campaigns for the Slope Imaging Multi-Polarization Photon Counting Lidar (SIMPL) instrument, and at the time of this reporting is at a technology readiness level of between 5 and 6. The laser is a 1,064-nm microchip high-repetition-rate laser emitting energy of about 8 microjoules per pulse. The beam was frequency-doubled to 532 nm using a KTP (KTiOPO4) nonlinear crystal [other nonlinear crystals such as LBO (LiB3O5) or periodically poled lithium niobiate can be used as well, depending on the conversion efficiency requirements], and the conversion efficiency was approximately 30 percent. The KTP was under temperature control using a thermoelectric cooler and a feedback monitoring thermistor. The dual-wavelength beams were then spectrally separated and each color went through its own optical path, which consisted of a beam-shaping lens, quarterwave plate (QWP), and a birefringent crystal (in this case, a calcite crystal, but others such as vanadate can be used). The QWP and calcite crystal set was used to convert the laser beams from a linearly polarized state to circularly polarized light, which when injected into a calcite crystal, will spatially separate the circularly polarized light into the two linear polarized components. The spatial separation of the two linearly polarized components is determined by the length of the crystal. A cond set of QWP and calcite then further separated the two beams into four. Additional sets of QWP and calcite can be used to further split the beams into multiple orders of two. The spatially separated beams had alternating linearly polarization states; a half-wave plate (HWP) array was then made to rotate the alternating states of

Generation of doubly charged vortex beam by concentrated loading of glass disks along their diameter.

PubMed

Skab, Ihor; Vasylkiv, Yuriy; Krupych, Oleh; Savaryn, Viktoriya; Vlokh, Rostyslav

2012-04-10

We show that a system of glass disks compressed along their diameters enables one to induce a doubly charged vortex beam in the emergent light when the incident light is circularly polarized. Using such a disk system, one can control the efficiency of conversion of the spin angular momentum to the orbital angular momentum by a loading force. The consideration presented here can be extended for the case of crystalline materials with high optical damage thresholds in order to induce high-power vortex beams.

High Energy electron and proton acceleration by circularly polarized laser pulse from near critical density hydrogen gas target.

PubMed

Sharma, Ashutosh

2018-02-01

Relativistic electron rings hold the possibility of very high accelerating rates, and hopefully a relatively cheap and compact accelerator/collimator for ultrahigh energy proton source. In this work, we investigate the generation of helical shaped quasi-monoenergetic relativistic electron beam and high-energy proton beam from near critical density plasmas driven by petawatt-circularly polarized-short laser pulses. We numerically observe the efficient proton acceleration from magnetic vortex acceleration mechanism by using the three dimensional particle-in-cell simulations; proton beam with peak energy 350 MeV, charge ~10nC and conversion efficiency more than 6% (which implies 2.4 J proton beam out of the 40 J incident laser energy) is reported. We detailed the microphysics involved in the ion acceleration mechanism, which requires investigating the role of self-generated plasma electric and magnetic fields. The concept of efficient generation of quasi-monoenergetic electron and proton beam from near critical density gas targets may be verified experimentally at advanced high power - high repetition rate laser facilities e.g. ELI-ALPS. Such study should be an important step towards the development of high quality electron and proton beam.

Plasma q -plate for generation and manipulation of intense optical vortices

DOE PAGES

Qu, Kenan; Jia, Qing; Fisch, Nathaniel J.

2017-11-28

An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here in this paper, we propose the design of suitably magnetized plasmas which, functioning as a q-plate, leads to a direct conversion from a high-intensity Gaussian beam into amore » twisted beam. A circularly polarized laser beam in the plasma accumulates an azimuthal-angle-dependent phase shift and hence forms a twisting wavefront. Our three-dimensional particle-in-cell simulations demonstrate extremely high-power conversion efficiency. The plasma q-plate can work in a large range of frequencies spanning from terahertz to the optical domain.« less

Plasma q -plate for generation and manipulation of intense optical vortices

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

Qu, Kenan; Jia, Qing; Fisch, Nathaniel J.

An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here in this paper, we propose the design of suitably magnetized plasmas which, functioning as a q-plate, leads to a direct conversion from a high-intensity Gaussian beam into amore » twisted beam. A circularly polarized laser beam in the plasma accumulates an azimuthal-angle-dependent phase shift and hence forms a twisting wavefront. Our three-dimensional particle-in-cell simulations demonstrate extremely high-power conversion efficiency. The plasma q-plate can work in a large range of frequencies spanning from terahertz to the optical domain.« less

Radiation energy conversion in space; Conference, 3rd, NASA Ames Research Center, Moffett Field, Calif., January 26-28, 1978, Technical Papers

NASA Technical Reports Server (NTRS)

Billman, K. W.

1978-01-01

Concepts for space-based conversion of space radiation energy into useful energy for man's needs are developed and supported by studies of costs, material and size requirements, efficiency, and available technology. Besides the more studied solar power satellite system using microwave transmission, a number of alternative space energy concepts are considered. Topics covered include orbiting mirrors for terrestrial energy supply, energy conversion at a lunar polar site, ultralightweight structures for space power, radiatively sustained cesium plasmas for solar electric conversion, solar pumped CW CO2 laser, superelastic laser energy conversion, laser-enhanced dynamics in molecular rate processes, and electron beams in space for energy storage.

Low-frequency acousto-optic backscattering of Bessel light beams

NASA Astrophysics Data System (ADS)

Khilo, Nikolai A.; Belyi, Vladimir N.; Khilo, Petr A.; Kazak, Nikolai S.

2018-05-01

The use of Bessel light beams, as well as Bessel acoustic beams, substantially enhances the capabilities of acousto-optic methods for control of optical field. We present a theoretical study of the process of optical Bessel beams conversion by means of backward acousto-optic scattering on a Bessel acoustic field in a transversely isotropic crystal. It is shown that, with an appropriate choice of Bessel beams parameters, the backscattering in visible spectral range can be realized at relatively low acoustic frequencies less than one gigahertz. Under conditions of phase matching and transverse spatial synchronism, the efficiency of backscattering is sufficiently high, which is interesting, for example, for construction of acousto-optic spectral analyzers.

SU-F-J-193: Efficient Dose Extinction Method for Water Equivalent Path Length (WEPL) of Real Tissue Samples for Validation of CT HU to Stopping Power Conversion

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

Zhang, R; Baer, E; Jee, K

Purpose: For proton therapy, an accurate model of CT HU to relative stopping power (RSP) conversion is essential. In current practice, validation of these models relies solely on measurements of tissue substitutes with standard compositions. Validation based on real tissue samples would be much more direct and can address variations between patients. This study intends to develop an efficient and accurate system based on the concept of dose extinction to measure WEPL and retrieve RSP in biological tissue in large number of types. Methods: A broad AP proton beam delivering a spread out Bragg peak (SOBP) is used to irradiatemore » the samples with a Matrixx detector positioned immediately below. A water tank was placed on top of the samples, with the water level controllable in sub-millimeter by a remotely controlled dosing pump. While gradually lowering the water level with beam on, the transmission dose was recorded at 1 frame/sec. The WEPL were determined as the difference between the known beam range of the delivered SOBP (80%) and the water level corresponding to 80% of measured dose profiles in time. A Gammex 467 phantom was used to test the system and various types of biological tissue was measured. Results: RSP for all Gammex inserts, expect the one made with lung-450 material (<2% error), were determined within ±0.5% error. Depends on the WEPL of investigated phantom, a measurement takes around 10 min, which can be accelerated by a faster pump. Conclusion: Based on the concept of dose extinction, a system was explored to measure WEPL efficiently and accurately for a large number of samples. This allows the validation of CT HU to stopping power conversions based on large number of samples and real tissues. It also allows the assessment of beam uncertainties due to variations over patients, which issue has never been sufficiently studied before.« less

High-efficiency GaAs and GaInP solar cells grown by all solid-state molecular-beam-epitaxy

PubMed Central

2011-01-01

We report the initial results of GaAs and GaInP solar cells grown by all solid-state molecular-beam-epitaxy (MBE) technique. For GaAs single-junction solar cell, with the application of AlInP as the window layer and GaInP as the back surface field layer, the photovoltaic conversion efficiency of 26% at one sun concentration and air mass 1.5 global (AM1.5G) is realized. The efficiency of 16.4% is also reached for GaInP solar cell. Our results demonstrate that the MBE-grown phosphide-contained III-V compound semiconductor solar cell can be quite comparable to the metal-organic-chemical-vapor-deposition-grown high-efficiency solar cell. PMID:22040124

Four-wave parametric oscillation in sodium vapor by electromagnetically induced diffraction.

PubMed

Harada, Ken-ichi; Ogata, Minoru; Mitsunaga, Masaharu

2007-05-01

We have observed a novel type of parametric oscillation in sodium atomic vapor where four off-axis signal waves simultaneously build up under resonant and counterpropagating pump beams with elliptical beam profiles. The four waves, two of them Stokes shifted and the other two anti-Stokes shifted, have similar output powers of up to 10 mW with a conversion efficiency of 30% and are parametrically coupled by electromagnetically induced diffraction.

Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

NASA Astrophysics Data System (ADS)

Yang, Hui; Deng, Yan

2017-12-01

All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

Design analysis and simulation study of an efficiency enhanced L-band MILO

NASA Astrophysics Data System (ADS)

Dixit, Gargi; Kumar, Arjun; Jain, P. K.

2017-01-01

In this article, an experimental L-band compact magnetically insulated transmission line oscillator (MILO) has been simulated using the 3D PIC simulation code "Particle Studio," and an improvement in the device efficiency has been obtained. The detailed interaction and operating mechanism describing the role of sub-assemblies have been explained. The performance of the device was found to be the function of the distance between the end-surface of the cathode and the beam-dump disk. During simulation, a high power microwave of the TM01 mode is generated with the peak RF-power of 6 GW and the power conversion efficiency of 19.2%, at the operating voltage of ˜600 kV and at the current of 52 kA. For better impedance matching or maximum power transfer, four stubs have been placed at the λg/4 distance from the extractor cavity, which results in the stable RF power output. In this work, an improved L-band MILO along with a new type beam-dump disk is selected for performance improvement with typical design parameters and beam parameters. The total peak power of improved MILO is 7 GW, and the maximum power conversion efficiency is 22.4%. This improvement is achieved due to the formation of the virtual cathode at the load side, which helps in modulating the energy of electrons owing to maximum reflection of electrons from the mesh or foil.

Quantum optical measurement with tripartite entangled photons generated by triple parametric down-conversion

NASA Astrophysics Data System (ADS)

Cho, Minhaeng

2018-05-01

Parametric down-conversion is a second-order nonlinear optical process annihilating a pump photon and creating a pair of photons in the signal and idler modes. Then, by using two parametric down-converters and introducing a path indistinguishability for the two generated idler modes, a quantum coherence between two conjugate signal beams can be induced. Such a double spontaneous or stimulated parametric down-conversion scheme has been used to demonstrate quantum spectroscopy and imaging with undetected idler photons via measuring one-photon interference between their correlated signal beams. Recently, we considered another quantum optical measurement scheme utilizing W-type tripartite entangled signal photons that can be generated by employing three spontaneous parametric down-conversion crystals and by inducing coherences or path-indistinguishabilities between their correlated idler beams and between quantum vacuum fields. Here, we consider an extended triple stimulated parametric down-conversion scheme for quantum optical measurement of sample properties with undetected idler and photons. Noting the real effect of vacuum field indistinguishability on the fringe visibility as well as the role of zero-point field energy in the interferometry, we show that this scheme is an ideal and efficient way to create a coherent state of W-type entangled signal photons. We anticipate that this scheme would be of critical use in further developing quantum optical measurements in spectroscopy and microscopy with undetected photons.

Quantum optical measurement with tripartite entangled photons generated by triple parametric down-conversion.

PubMed

Cho, Minhaeng

2018-05-14

Parametric down-conversion is a second-order nonlinear optical process annihilating a pump photon and creating a pair of photons in the signal and idler modes. Then, by using two parametric down-converters and introducing a path indistinguishability for the two generated idler modes, a quantum coherence between two conjugate signal beams can be induced. Such a double spontaneous or stimulated parametric down-conversion scheme has been used to demonstrate quantum spectroscopy and imaging with undetected idler photons via measuring one-photon interference between their correlated signal beams. Recently, we considered another quantum optical measurement scheme utilizing W-type tripartite entangled signal photons that can be generated by employing three spontaneous parametric down-conversion crystals and by inducing coherences or path-indistinguishabilities between their correlated idler beams and between quantum vacuum fields. Here, we consider an extended triple stimulated parametric down-conversion scheme for quantum optical measurement of sample properties with undetected idler and photons. Noting the real effect of vacuum field indistinguishability on the fringe visibility as well as the role of zero-point field energy in the interferometry, we show that this scheme is an ideal and efficient way to create a coherent state of W-type entangled signal photons. We anticipate that this scheme would be of critical use in further developing quantum optical measurements in spectroscopy and microscopy with undetected photons.

Nuclear-Pumped Lasers. [efficient conversion of energy liberated in nuclear reactions to coherent radiation

NASA Technical Reports Server (NTRS)

1979-01-01

The state of the art in nuclear pumped lasers is reviewed. Nuclear pumped laser modeling, nuclear volume and foil excitation of laser plasmas, proton beam simulations, nuclear flashlamp excitation, and reactor laser systems studies are covered.

High-power 671  nm laser by second-harmonic generation with 93% efficiency in an external ring cavity.

PubMed

Cui, Xing-Yang; Shen, Qi; Yan, Mei-Chen; Zeng, Chao; Yuan, Tao; Zhang, Wen-Zhuo; Yao, Xing-Can; Peng, Cheng-Zhi; Jiang, Xiao; Chen, Yu-Ao; Pan, Jian-Wei

2018-04-15

Second-harmonic generation (SHG) is useful for obtaining single-frequency continuous-wave laser sources at various wavelengths for applications ranging from biology to fundamental physics. Using an external power-enhancement cavity is an effective approach to improve the frequency conversion efficiency. However, thermal effects limit the efficiency, particularly, in high-power operation. Therefore, reducing thermal effects is important when designing a cavity. This Letter reports the use of an external ring cavity for SHG, yielding a 5.2 W, 671 nm laser light with a conversion efficiency of 93.8±0.8% which, to the best of our knowledge, is a new record of conversion efficiency for an external ring cavity. It is achieved using a 10 mm length periodically poled potassium titanyl phosphate crystal and a 65 μm radius beam waist in the cavity so as to minimize thermal dephasing and thermal lensing. Furthermore, a method is developed to determine a conversion efficiency more accurately based on measuring the pump depletion using a photodiode detector and a maximum pump depletion up to 97% is recorded. In this method, the uncertainty is much less than that achieved in a common method by direct measuring with a power meter.

K-space polarimetry of bullseye plasmon antennas

PubMed Central

Osorio, Clara I.; Mohtashami, Abbas; Koenderink, A. Femius

2015-01-01

Surface plasmon resonators can drastically redistribute incident light over different output wave vectors and polarizations. This can lead for instance to sub-diffraction sized nanoapertures in metal films that beam and to nanoparticle antennas that enable efficient conversion of photons between spatial modes, or helicity channels. We present a polarimetric Fourier microscope as a new experimental tool to completely characterize the angle-dependent polarization-resolved scattering of single nanostructures. Polarimetry allows determining the full Stokes parameters from just six Fourier images. The degree of polarization and the polarization ellipse are measured for each scattering direction collected by a high NA objective. We showcase the method on plasmonic bullseye antennas in a metal film, which are known to beam light efficiently. We find rich results for the polarization state of the beamed light, including complete conversion of input polarization from linear to circular and from one helicity to another. In addition to uncovering new physics for plasmonic groove antennas, the described technique projects to have a large impact in nanophotonics, in particular towards the investigation of a broad range of phenomena ranging from photon spin Hall effects, polarization to orbital angular momentum transfer and design of plasmon antennas. PMID:25927570

K-space polarimetry of bullseye plasmon antennas.

PubMed

Osorio, Clara I; Mohtashami, Abbas; Koenderink, A Femius

2015-04-30

Surface plasmon resonators can drastically redistribute incident light over different output wave vectors and polarizations. This can lead for instance to sub-diffraction sized nanoapertures in metal films that beam and to nanoparticle antennas that enable efficient conversion of photons between spatial modes, or helicity channels. We present a polarimetric Fourier microscope as a new experimental tool to completely characterize the angle-dependent polarization-resolved scattering of single nanostructures. Polarimetry allows determining the full Stokes parameters from just six Fourier images. The degree of polarization and the polarization ellipse are measured for each scattering direction collected by a high NA objective. We showcase the method on plasmonic bullseye antennas in a metal film, which are known to beam light efficiently. We find rich results for the polarization state of the beamed light, including complete conversion of input polarization from linear to circular and from one helicity to another. In addition to uncovering new physics for plasmonic groove antennas, the described technique projects to have a large impact in nanophotonics, in particular towards the investigation of a broad range of phenomena ranging from photon spin Hall effects, polarization to orbital angular momentum transfer and design of plasmon antennas.

Simulations of a beam-driven plasma antenna in the regime of plasma transparency

NASA Astrophysics Data System (ADS)

Timofeev, I. V.; Berendeev, E. A.; Dudnikova, G. I.

2017-09-01

In this paper, the theoretically predicted possibility to increase the efficiency of electromagnetic radiation generated by a thin beam-plasma system in the regime of oblique emission, when a plasma column becomes transparent to radiation near the plasma frequency, is investigated using particle-in-cell simulations. If a finite-size plasma column has a longitudinal density modulation, such a system is able to radiate electromagnetic waves as a dipole antenna. This radiation mechanism is based on the conversion of an electron beam-driven potential plasma wave on the periodic perturbation of plasma density. In this case, the frequency of radiated waves appears to be slightly lower than the plasma frequency. That is why their fields enable the penetration into the plasma only to the skin-depth. This case is realized when the period of density modulation coincides with the wavelength of the most unstable beam-driven mode, and the produced radiation escapes from the plasma in the purely transverse direction. In the recent theoretical paper [I. V. Timofeev et al. Phys. Plasmas 23, 083119 (2016)], however, it has been found that the magnetized plasma can be transparent to this radiation at certain emission angles. It means that the beam-to-radiation power conversion can be highly efficient even in a relatively thick plasma since not only boundary layers but also the whole plasma volume can be involved in the generation of electromagnetic waves. Simulations of steady-state beam injection into a pre-modulated plasma channel confirm the existence of this effect and show limits of validity for the simplified theoretical model.

The Electron Bernstein Waves Heating Project In The TJ-II Stellarator

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

Fernandez, A.; Cappa, A.; Castejon, F.

2007-09-28

TJ-II is a middle sized flexible Heliac operating in Madrid, whose plasmas are created and heated by ECRH via two 300 kW gyrotrons at second harmonic X-mode (53.2 GHz). Neutral beam injection is used for second phase heating. Since the cut off density for the 2nd harmonic X-mode (n{sub c} = 1.7x10 {sup 19} m{sup -3}) is reached during NBI, EBWs are considered both for providing additional heating after NBI switch on and to perform kinetic studies in high-density plasmas. Previous work has shown that the most suitable scheme for launching EBWs in TJ-II is O-X-B mode conversion, which hasmore » acceptable heating efficiency for central densities above 1.2x10{sup 19} m{sup -3}, with an operating frequency of 28 GHz. In this work, the most relevant theoretical calculations are presented, including the relativistic effects both in ray trajectory and absorption, as well as the results of the optimization of the beam parameters that provide the maximum O-X conversion efficiency at the critical layer. A system based on a 28 GHz-100 ms diode gyrotron will be used to deliver 300 kW through a corrugated waveguide. The microwave beam is directed and focused by a steerable mirror located inside the vacuum vessel. A diagnostic for measuring the EBW emission has been designed and tested on the bench. It uses a section of corrugated waveguide and a glass lens to focus the emission from the plasma into the aperture of a dual polarized quad-ridged horn. It will allow us to determine the EBW mode conversion efficiency, and also provides an indication of the electron temperature evolution in overdense plasmas.« less

2 W quasi-white-light based on idler-resonant optical parametric oscillation cascading sum-frequency generation with PPSLT

NASA Astrophysics Data System (ADS)

Zhao, L. N.; Liu, J.; Yuan, Y.; Hu, X. P.; Zhao, G.; Gao, Z. D.; Zhu, S. N.

2012-03-01

We present a high power red-green-blue (RGB) laser light source based on cascaded quasi-phasematched wavelength conversions in a single stoichiometric lithium tantalate. The superiority of the experimental setup is: the facula of the incident beam is elliptical to increase interaction volume, and the cavity was an idler resonant configuration for realizing more efficient red and blue light output. An average power of 2 W of quasi-white-light was obtained by proper combination of the RGB three colors. The conversion efficiency for the power of the quasi-white-light over pump power reached 36%. This efficiency and powerful RGB laser light source has potential applications in laser-based projection display et al.

Parametric amplification of orbital angular momentum beams based on light-acoustic interaction

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

Gao, Wei, E-mail: wei-g@163.com, E-mail: zhuzhihandd@sina.com; Mu, Chunyuan; Yang, Yuqiang

A high fidelity amplification of beams carrying orbital angular momentum (OAM) is very crucial for OAM multiplexing and other OAM-based applications. Here, we report a demonstration of stimulated Brillouin amplification for OAM beams, and the energy conversion efficiency of photon-phonon coupling and the phase structure of amplified signals are investigated in collinear and noncollinear frame systems, respectively. Our results demonstrate that the OAM signals can be efficiently amplified without obvious noise introduced, and the modes of output signal are independent of the pump modes or the geometrical frames. Meanwhile, an OAM state depending on the optical modes and the geometricalmore » frames is loaded into phonons by coherent light-acoustic interaction, which reveals more fundamental significance and a great application potential in OAM-multiplexing.« less

Direct-Write Fabrication of Cellulose Nano-Structures via Focused Electron Beam Induced Nanosynthesis

PubMed Central

Ganner, Thomas; Sattelkow, Jürgen; Rumpf, Bernhard; Eibinger, Manuel; Reishofer, David; Winkler, Robert; Nidetzky, Bernd; Spirk, Stefan; Plank, Harald

2016-01-01

In many areas of science and technology, patterned films and surfaces play a key role in engineering and development of advanced materials. Here, we introduce a new generic technique for the fabrication of polysaccharide nano-structures via focused electron beam induced conversion (FEBIC). For the proof of principle, organosoluble trimethylsilyl-cellulose (TMSC) thin films have been deposited by spin coating on SiO2 / Si and exposed to a nano-sized electron beam. It turns out that in the exposed areas an electron induced desilylation reaction takes place converting soluble TMSC to rather insoluble cellulose. After removal of the unexposed TMSC areas, structured cellulose patterns remain on the surface with FWHM line widths down to 70 nm. Systematic FEBIC parameter sweeps reveal a generally electron dose dependent behavior with three working regimes: incomplete conversion, ideal doses and over exposure. Direct (FT-IR) and indirect chemical analyses (enzymatic degradation) confirmed the cellulosic character of ideally converted areas. These investigations are complemented by a theoretical model which suggests a two-step reaction process by means of TMSC → cellulose and cellulose → non-cellulose material conversion in excellent agreement with experimental data. The extracted, individual reaction rates allowed the derivation of design rules for FEBIC parameters towards highest conversion efficiencies and highest lateral resolution. PMID:27585861

Diffractive optical elements for transformation of modes in lasers

DOEpatents

Sridharan, Arun K.; Pax, Paul H.; Heebner, John E.; Drachenberg, Derrek R.; Armstrong, James P.; Dawson, Jay W.

2015-09-01

Spatial mode conversion modules are described, with the capability of efficiently transforming a given optical beam profile, at one plane in space into another well-defined optical beam profile at a different plane in space, whose detailed spatial features and symmetry properties can, in general, differ significantly. The modules are comprised of passive, high-efficiency, low-loss diffractive optical elements, combined with Fourier transform optics. Design rules are described that employ phase retrieval techniques and associated algorithms to determine the necessary profiles of the diffractive optical components. System augmentations are described that utilize real-time adaptive optical techniques for enhanced performance as well as power scaling.

Diffractive optical elements for transformation of modes in lasers

DOEpatents

Sridharan, Arun K; Pax, Paul H; Heebner, John E; Drachenberg, Derrek R.; Armstrong, James P.; Dawson, Jay W.

2016-06-21

Spatial mode conversion modules are described, with the capability of efficiently transforming a given optical beam profile, at one plane in space into another well-defined optical beam profile at a different plane in space, whose detailed spatial features and symmetry properties can, in general, differ significantly. The modules are comprised of passive, high-efficiency, low-loss diffractive optical elements, combined with Fourier transform optics. Design rules are described that employ phase retrieval techniques and associated algorithms to determine the necessary profiles of the diffractive optical components. System augmentations are described that utilize real-time adaptive optical techniques for enhanced performance as well as power scaling.

High-power microwave production by gyroharmonic conversion and co-generation

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

LaPointe, M.A.; Yoder, R.B.; Wang, M.

1997-03-01

An rf accelerator that adds significant gyration energy to a relativistic electron beam, and mechanisms for extracting coherent radiation from the beam, are described. The accelerator is a cyclotron autoresonance accelerator (CARA), underlying theory and experimental tests of which are reviewed. The measurements illustrate the utility of CARA in preparing beams for high harmonic gyro interactions. Examples of preparation of gyrating axis-encircling beams of {approximately}400kV, 25 A with 1{lt}a{lt}2 using a 2.856 GHz CARA are discussed. Generation of MW-level harmonic power emanating from a beam prepared in CARA into an output cavity structure is predicted by theory. First measurements ofmore » intense superradiant 2nd through 6th harmonic emission from a CARA beam are described. Gyroharmonic conversion (GHC) at MW power levels into an appropriate resonator can be anticipated, in view of the results described here. Another radiation mechanism, closely related to GHC, is also described. This mechanism, dubbed {open_quotes}co-generation,{close_quotes} is based on the fact that the lowest TE{sub sm} mode in a cylindrical waveguide at frequency sw with group velocity nearly identical to group velocity for the TE{sub 11} mode at frequency w is that with s=7, m=2. This allows coherent radiation to be generated at the 7th harmonic co-existent with CARA and in the self-same rf structure. Conditions are found where co-generation of 7th harmonic power at 20 GHz is possible with overall efficiency greater than 80{percent}. It is shown that operation of a cw co-generator can take place without need of a power supply for the gun. Efficiency for a multi-MW 20 GHz co-generator is predicted to be high enough to compete with other sources, even after taking into account the finite efficiency of the rf driver required for CARA. {copyright} {ital 1997 American Institute of Physics.}« less

Design of a high efficiency relativistic backward wave oscillator with low guiding magnetic field

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

Li, Xiaoze; Song, Wei; Tan, Weibing

2016-07-15

A high efficiency relativistic backward wave oscillator working at a low guiding magnetic field is designed and simulated. A trapezoidal resonant reflector is used to reduce the modulation field in the resonant reflector to avoid overmodulation of the electron beam which will lead to a large momentum spread and then low conversion efficiency. The envelope of the inner radius of the slow wave structure (SWS) increases stepwise to keep conformal to the trajectory of the electron beam which will alleviate the bombardment of the electron on the surface of the SWS. The length of period of the SWS is reducedmore » gradually to make a better match between phase velocity and electron beam, which decelerates continually and improves the RF current distribution. Meanwhile the modulation field is reduced by the introduction of nonuniform SWS also. The particle in cell simulation results reveal that a microwave with a power of 1.8 GW and a frequency of 14.7 GHz is generated with an efficiency of 47% when the diode voltage is 620 kV, the beam current 6.1 kA, and the guiding magnetic field 0.95 T.« less

Laser beam combining and cleanup by stimulated Brillouin scattering in a multimode optical fiber.

PubMed

Rodgers, B C; Russell, T H; Roh, W B

1999-08-15

A new technique for combining low-power laser beams has been demonstrated by use of semiconductor diode lasers. The technique, which is appropriate for any single-longitudinal-mode laser, is based on stimulated Brillouin scattering (SBS) in long multimode optical fibers. It produces a clean Gaussian-like beam that corresponds to the fundamental fiber mode, irrespective of the profile of the pump. Coherent as well as incoherent combining was demonstrated, and conversion slope efficiencies as high as 67% and 83% were shown to be achievable for the single-pass and ring-cavity SBS geometries, respectively.

FusionArc optimization: a hybrid volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) planning strategy.

PubMed

Matuszak, Martha M; Steers, Jennifer M; Long, Troy; McShan, Daniel L; Fraass, Benedick A; Romeijn, H Edwin; Ten Haken, Randall K

2013-07-01

To introduce a hybrid volumetric modulated arc therapy/intensity modulated radiation therapy (VMAT/IMRT) optimization strategy called FusionArc that combines the delivery efficiency of single-arc VMAT with the potentially desirable intensity modulation possible with IMRT. A beamlet-based inverse planning system was enhanced to combine the advantages of VMAT and IMRT into one comprehensive technique. In the hybrid strategy, baseline single-arc VMAT plans are optimized and then the current cost function gradients with respect to the beamlets are used to define a metric for predicting which beam angles would benefit from further intensity modulation. Beams with the highest metric values (called the gradient factor) are converted from VMAT apertures to IMRT fluence, and the optimization proceeds with the mixed variable set until convergence or until additional beams are selected for conversion. One phantom and two clinical cases were used to validate the gradient factor and characterize the FusionArc strategy. Comparisons were made between standard IMRT, single-arc VMAT, and FusionArc plans with one to five IMRT∕hybrid beams. The gradient factor was found to be highly predictive of the VMAT angles that would benefit plan quality the most from beam modulation. Over the three cases studied, a FusionArc plan with three converted beams achieved superior dosimetric quality with reductions in final cost ranging from 26.4% to 48.1% compared to single-arc VMAT. Additionally, the three beam FusionArc plans required 22.4%-43.7% fewer MU∕Gy than a seven beam IMRT plan. While the FusionArc plans with five converted beams offer larger reductions in final cost--32.9%-55.2% compared to single-arc VMAT--the decrease in MU∕Gy compared to IMRT was noticeably smaller at 12.2%-18.5%, when compared to IMRT. A hybrid VMAT∕IMRT strategy was implemented to find a high quality compromise between gantry-angle and intensity-based degrees of freedom. This optimization method will allow patients to be simultaneously planned for dosimetric quality and delivery efficiency without switching between delivery techniques. Example phantom and clinical cases suggest that the conversion of only three VMAT segments to modulated beams may result in a good combination of quality and efficiency.

Isotope separation by selective charge conversion and field deflection

DOEpatents

Hickman, Robert G.

1978-01-01

A deuterium-tritium separation system wherein a source beam comprised of positively ionized deuterium (D.sup.+) and tritium (T.sup.+) is converted at different charge-exchange cell sections of the system to negatively ionized deuterium (D.sup.-) and tritium (T.sup.-). First, energy is added to the beam to accelerate the D.sup.+ ions to the velocity that is optimum for conversion of the D.sup.+ ions to D.sup.- ions in a charge-exchange cell. The T.sup.+ ions are accelerated at the same time, but not to the optimum velocity since they are heavier than the D.sup.+ ions. The T.sup.+ ions are, therefore, not converted to T.sup.- ions when the D.sup.+ ions are converted to D.sup.- ions. This enables effective separation of the beam by deflection of the isotopes with an electrostatic field, the D.sup.- ions being deflected in one direction and the T.sup.+ ions being deflected in the opposite direction. Next, more energy is added to the deflected beam of T.sup.+ ions to bring the T.sup.+ ions to the optimum velocity for their conversion to T.sup.- ions. In a particular use of the invention, the beams of D.sup.- and T.sup.- ions are separately further accelerated and then converted to energetic neutral particles for injection as fuel into a thermonuclear reactor. The reactor exhaust of D.sup.+ and T.sup.+ and the D.sup.+ and T.sup.+ that was not converted in the respective sections is combined with the source beam and recycled through the system to increase the efficiency of the system.

Chemical beam epitaxy for high efficiency photovoltaic devices

NASA Technical Reports Server (NTRS)

Bensaoula, A.; Freundlich, A.; Vilela, M. F.; Medelci, N.; Renaud, P.

1994-01-01

InP-based multijunction tandem solar cells show great promise for the conversion efficiency (eta) and high radiation resistance. InP and its related ternary and quanternary compound semiconductors such as InGaAs and InGaAsP offer desirable combinations for energy bandgap values which are very suitable for multijunction tandem solar cell applications. The monolithically integrated InP/In(0.53)Ga(0.47)As tandem solar cells are expected to reach efficiencies above 30 percent. Wanlass, et.al., have reported AMO efficiencies as high as 20.1% for two terminal cells fabricated using atmospheric-pressure metalorganic vapor phase epitaxy (APMOVPE). The main limitations in their technique are first related to the degradation of the intercell ohmic contact (IOC), in this case the In(0.53)Ga(0.47)As tunnel junction during the growth of the top InP subcell structure, and second to the current matching, often limited by the In(0.53)Ga(0.47)As bottom subcell. Chemical beam epitaxy (CBE) has been shown to allow the growth of high quality materials with reproducible complex compositional and doping profiles. The main advantage of CBE compared to metalorganic chemical vapor deposition (MOCVD), the most popular technique for InP-based photovoltaic device fabrication, is the ability to grow high purity epilayers at much lower temperatures (450 C - 530 C). In a recent report it was shown that cost-wise CBE is a breakthrough technology for photovoltaic (PV) solar energy progress in the energy conversion efficiency of InP-based solar cells fabricated using chemical beam epitaxy. This communication summarizes our recent results on PV devices and demonstrates the strength of this new technology.

A Numerical Simulation of the Energy Conversion Process in Microwave Rocket

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

Shibata, Teppei; Oda, Yasuhisa; Komurasaki, Kimiya

2008-04-28

In Microwave Rocket, a high power microwave beam ionizes atmospheric air inside of the thruster and the ionization front drives a shock wave. In this paper, CFD simulation was conducted using measured propagation velocity of the ionization front to evaluate the engine performance. As a result, maximum cycle efficiency was obtained at the power density of about 200 kW/m{sup 2} which is the transitional beam power condition between Microwave Supported Combustion and Microwave Supported Detonation regimes.

A novel coaxial Ku-band transit radiation oscillator without external guiding magnetic field

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

Ling, Junpu, E-mail: lingjunpu@163.com; Zhang, Jiande; He, Juntao

2014-02-15

A novel coaxial transit radiation oscillator without external guiding magnetic field is designed to generate high power microwave at Ku-band. By using a coaxial structure, the space-charge potential energy is suppressed significantly, that is good for enhancing efficient beam-wave interaction. In order to improve the transmission stability of the unmagnetized intense relativistic electron beam, a Pierce-like cathode is employed in the novel device. By contrast with conventional relativistic microwave generators, this kind of device has the advantages of high stability, non-guiding magnetic field, and high efficiency. Moreover, with the coaxial design, it is possible to improve the power-handing capacity bymore » increasing the radial dimension of the Ku-band device. With a 550 keV and 7.5 kA electron beam, a 1.25 GW microwave pulse at 12.08 GHz has been obtained in the simulation. The power conversion efficiency is about 30%.« less

Dual-cavity mode converter for a fundamental mode output in an over-moded relativistic backward-wave oscillator

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

Li, Jiawei; Huang, Wenhua; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024

2015-03-16

A dual-cavity TM{sub 02}–TM{sub 01} mode converter is designed for a dual-mode operation over-moded relativistic backward-wave oscillator. With the converter, the fundamental mode output is achieved. Particle-in-cell simulation shows that the efficiency of beam-wave conversion was over 46% and a pureTM{sub 01} mode output was obtained. Effects of end reflection provided by the mode converter were studied. Adequate TM{sub 01} mode feedback provided by the converter enhances conversion efficiency. The distance between the mode converter and extraction cavity critically affect the generation of microwaves depending on the reflection phase of TM{sub 01} mode feedback.

Improved power and efficiency for tapered lasers with optimized photonic crystal structures

NASA Astrophysics Data System (ADS)

Ma, Xiaolong; Qu, Hongwei; Zhao, Shaoyu; Zhou, Xuyan; Lin, Yuzhe; Zheng, Wanhua

2017-10-01

High power and high beam quality laser sources are required in numerous applications such as nonlinear frequency conversion, optical pumping of solid-state and fiber lasers, material processing and others. Tapered lasers can provide a high output power while keeping a high beam quality. However, the conventional tapered lasers suffer from a large vertical beam divergence. We have demonstrated 2-mm long tapered lasers with photonic crystal structures. A high beam quality and a narrow vertical divergence are achieved. In this paper, we optimized the photonic crystal structure and fabricated a 4-mm long tapered laser to further increase the output power and the wall-plug efficiency. Compared with our precious wafer, the optimized structure has a lower doping level to reduce the internal loss. The period of the photonic crystal structure and the thickness of the upper cladding are also reduced. The device has a 1-mm long ridge-waveguide section and a 3-mm long tapered section. The taper angle is 4°. An output power of 7.3 W is achieved with a peak wall-plug efficiency of 46% in continuous-wave mode. The threshold current is around 500 mA and the slope efficiency is 0.93 W/A. In pulsed mode, the output power is 15.6 W and the maximum wall-plug efficiency is 48.1%. The far-field divergence with full width at half maximum is 6.3° for the lateral direction at 3 A. The vertical far-field beam divergence is around 11° at different injection levels. High beam qualities are demonstrated by beam quality factor M2 of 1.52 for the lateral direction and 1.54 for the vertical direction.

Fabrication of photovoltaic laser energy converterby MBE

NASA Technical Reports Server (NTRS)

Lu, Hamilton; Wang, Scott; Chan, W. S.

1993-01-01

A laser-energy converter, fabricated by molecular beam epitaxy (MBE), was developed. This converter is a stack of vertical p-n junctions connected in series by low-resistivity, lattice matched CoSi2 layers to achieve a high conversion efficiency. Special high-temperature electron-beam (e-beam) sources were developed especially for the MBE growth of the junctions and CoSi2 layers. Making use of the small (greater than 1.2 percent) lattice mismatch between CoSi2 and Si layers, high-quality and pinhole-free epilayers were achieved, providing a capability of fabricating all the junctions and connecting layers as a single growth process with one pumpdown. Well-defined multiple p-n junctions connected by CoSi2 layers were accomplished by employing a low growth temperature (greater than 700 C) and a low growth rate (less than 0.5 microns/hour). Producing negligible interdiffusion, the low growth temperature and rate also produced negligible pinholes in the CoSi2 layers. For the first time, a stack of three p-n junctions connected by two 10(exp -5) Ohm-cm CoSi2 layers was achieved, meeting the high conversion efficiency requirement. This process can now be optimized for high growth rate to form a practical converter with 10 p-n junctions in the stack.

An energy harvesting solution based on the post-buckling response of non-prismatic slender beams

NASA Astrophysics Data System (ADS)

Jiao, Pengcheng; Borchani, Wassim; Hasni, Hassene; Alavi, Amir H.; Lajnef, Nizar

2017-04-01

Systems based on post-buckled structural elements have been extensively used in many applications such as actuation, remote sensing and energy harvesting thanks to their efficiency enhancement. The post-buckling snap- through behavior of bilaterally constrained beams has been used to create an efficient energy harvesting mechanism under quasi-static excitations. The conversion mechanism has been used to transform low-rate and low-frequency excitations into high-rate motions. Electric energy can be generated from such high-rate motions using piezoelectric transducers. However, lack of control over the post-buckling behavior severely limits the mechanism's efficiency. This study aims to maximize the levels of the harvestable power by controlling the location of the snapping point along the beam at different buckling transitions. Since the snap-through location cannot be controlled by tuning the geometry properties of a uniform cross-section beam, non-uniform cross sections are examined. An energy-based theoretical model is herein developed to predict the post-buckling response of non-uniform cross-section beams. The total potential energy is minimized under constraints that represent the physical confinement of the beam between the lateral boundaries. Experimentally validated results show that changing the shape and geometry dimensions of non- uniform cross-section beams allows for the accurate control of the snap-through location at different buckling transitions. A 78.59% increase in harvested energy levels is achieved by optimizing the beam's shape.

Non-classical Signature of Parametric Fluorescence and its Application in Metrology

NASA Astrophysics Data System (ADS)

Hamar, M.; Michálek, V.; Pathak, A.

2014-08-01

The article provides a short theoretical background of what the non-classical light means. We applied the criterion for the existence of non-classical effects derived by C.T. Lee on parametric fluorescence. The criterion was originally derived for the study of two light beams with one mode per beam. We checked if the criterion is still working for two multimode beams of parametric down-conversion through numerical simulations. The theoretical results were tested by measurement of photon number statistics of twin beams emitted by nonlinear BBO crystal pumped by intense femtoseconds UV pulse. We used ICCD camera as the detector of photons in both beams. It appears that the criterion can be used for the measurement of the quantum efficiencies of the ICCD cameras.

Regimes of enhanced electromagnetic emission in beam-plasma interactions

NASA Astrophysics Data System (ADS)

Timofeev, I. V.; Annenkov, V. V.; Arzhannikov, A. V.

2015-11-01

The ways to improve the efficiency of electromagnetic waves generation in laboratory experiments with high-current relativistic electron beams injected into a magnetized plasma are discussed. It is known that such a beam can lose, in a plasma, a significant part of its energy by exciting a high level of turbulence and heating plasma electrons. Beam-excited plasma oscillations may simultaneously participate in nonlinear processes resulting in a fundamental and second harmonic emissions. It is obvious, however, that in the developed plasma turbulence the role of these emissions in the total energy balance is always negligible. In this paper, we investigate whether electromagnetic radiation generated in the beam-plasma system can be sufficiently enhanced by the direct linear conversion of resonant beam-driven modes into electromagnetic ones on preformed regular inhomogeneities of plasma density. Due to the high power of relativistic electron beams, the mechanism discussed may become the basis for the generator of powerful sub-terahertz radiation.

Relaxed damage threshold intensity conditions and nonlinear increase in the conversion efficiency of an optical parametric oscillator using a bi-directional pump geometry.

PubMed

Norris, G; McConnell, G

2010-03-01

A novel bi-directional pump geometry that nonlinearly increases the nonlinear optical conversion efficiency of a synchronously pumped optical parametric oscillator (OPO) is reported. This bi-directional pumping method synchronizes the circulating signal pulse with two counter-propagating pump pulses within a linear OPO resonator. Through this pump scheme, an increase in nonlinear optical conversion efficiency of 22% was achieved at the signal wavelength, corresponding to a 95% overall increase in average power. Given an almost unchanged measured pulse duration of 260 fs under optimal performance conditions, this related to a signal wavelength peak power output of 18.8 kW, compared with 10 kW using the traditional single-pass geometry. In this study, a total effective peak intensity pump-field of 7.11 GW/cm(2) (corresponding to 3.55 GW/cm(2) from each pump beam) was applied to a 3 mm long periodically poled lithium niobate crystal, which had a damage threshold intensity of 4 GW/cm(2), without impairing crystal integrity. We therefore prove the application of this novel pump geometry provides opportunities for power-scaling of synchronously pumped OPO systems together with enhanced nonlinear conversion efficiency through relaxed damage threshold intensity conditions.

Laser source with high pulse energy at 3-5 μm and 8-12 μm based on nonlinear conversion in ZnGeP2

NASA Astrophysics Data System (ADS)

Lippert, Espen; Fonnum, Helge; Haakestad, Magnus W.

2014-10-01

We present a high energy infrared laser source where a Tm:fiber laser is used to pump a high-energy 2-μm cryogenically cooled Ho:YLF laser. We have achieved 550 mJ of output energy at 2.05 μm, and through non-linear conversion in ZnGeP2 generated 200 mJ in the 3-5-μm range. Using a numerical simulation tool we have also investigated a setup which should generate more than 70 mJ in the 8-12-μm range. The conversion stage uses a master-oscillator-power-amplifier architecture to enable high conversion efficiency and good beam quality.

Thermoelectronic laser energy conversion for power transmission in space

NASA Technical Reports Server (NTRS)

Britt, E. J.; Yuen, C.

1977-01-01

Long distance transmission of power in space by means of laser beams is an attractive concept because of the very narrow beam divergence. Such a system requires efficient means to both generate the laser beam and to convert the light energy in the beam into useful electric output at the receiver. A plasma-type device known as a Thermo-Electronic Laser Energy Converter (TELEC) has been studied as a method of converting a 10.6 micron CO2 laser beam into electric power. In the TELEC process, electromagnetic radiation is absorbed directly in the plasma electrons producing a high electron temperature. The energetic electrons diffuse out of the plasma striking two electrodes with different areas. Since more electrons are collected by the larger electrode there is a net transport of current, and an EMF is generated in the external circuit. The smaller electrode functions as an electron emitter to provide continuity of the current. Waste heat is rejected from the large electrode. A design for a TELEC system with an input 1 MW laser beam was developed as part of the study. The calculated performance of the system showed an overall efficiency of about 42%.

Stretched Lens Array (SLA) for Collection and Conversion of Infrared Laser Light: 45% Efficiency Demonstrated for Near-Term 800 W/kg Space Power System

NASA Technical Reports Server (NTRS)

O'Neill, Mark; Howell, Joe; Fikes, John; Fork, Richard; Phillips, Dane; Aiken, Dan; McDanal, A. J.

2006-01-01

For the past 2% years, our team has been developing a unique photovoltaic concentrator array for collection and conversion of infrared laser light. This laser-receiving array has evolved from the solar-receiving Stretched Lens Array (SLA). The laser-receiving version of SLA is being developed for space power applications when or where sunlight is not available (e.g., the eternally dark lunar polar craters). The laser-receiving SLA can efficiently collect and convert beamed laser power from orbiting spacecraft or other sources (e.g., solar-powered lasers on the permanently illuminated ridges of lunar polar craters). A dual-use version of SLA can produce power from sunlight during sunlit portions of the mission, and from beamed laser light during dark portions of the mission. SLA minimizes the cost and mass of photovoltaic cells by using gossamer-like Fresnel lenses to capture and focus incoming light (solar or laser) by a factor of 8.5X, thereby providing a cost-effective, ultra-light space power system.

p-BaSi2/n-Si heterojunction solar cells on Si(001) with conversion efficiency approaching 10%: comparison with Si(111)

NASA Astrophysics Data System (ADS)

Deng, Tianguo; Sato, Takuma; Xu, Zhihao; Takabe, Ryota; Yachi, Suguru; Yamashita, Yudai; Toko, Kaoru; Suemasu, Takashi

2018-06-01

B-doped p-BaSi2 epitaxial layers with a hole concentration of 1.1 × 1018 cm‑3 were grown on n-Si(001) using molecular beam epitaxy to fabricate p-BaSi2/n-Si solar cells. The thickness (d) of the p-BaSi2 layer was varied from 20 to 60 nm to investigate its effect on the solar cell performance. The conversion efficiency under an AM1.5 illumination increased with d reaching a maximum of 9.8% at d = 40 nm, which is nearly equal to the highest efficiency (9.9%) for p-BaSi2/n-Si solar cells on Si(111). This study indicated that Si(001) substrates are promising for use in BaSi2 solar cells.

3.1 W narrowband blue external cavity diode laser

NASA Astrophysics Data System (ADS)

Peng, Jue; Ren, Huaijin; Zhou, Kun; Li, Yi; Du, Weichuan; Gao, Songxin; Li, Ruijun; Liu, Jianping; Li, Deyao; Yang, Hui

2018-03-01

We reported a high-power narrowband blue diode laser which is suitable for subsequent nonlinear frequency conversion into the deep ultraviolet (DUV) spectral range. The laser is based on an external cavity diode laser (ECDL) system using a commercially available GaN-based high-power blue laser diode emitting at 448 nm. Longitudinal mode selection is realized by using a surface diffraction grating in Littrow configuration. The diffraction efficiency of the grating was optimized by controlling the polarization state of the laser beam incident on the grating. A maximum optical output power of 3.1 W in continuous-wave operation with a spectral width of 60 pm and a side-mode suppression ratio (SMSR) larger than 10 dB at 448.4 nm is achieved. Based on the experimental spectra and output powers, the theoretical efficiency and output power of the subsequent nonlinear frequency conversion were calculated according to the Boyd- Kleinman theory. The single-pass conversion efficiency and output power is expected to be 1.9×10-4 and 0.57 mW, respectively, at the 3.1 W output power of the ECDL. The high-power narrowband blue diode laser is very promising as pump source in the subsequent nonlinear frequency conversion.

Relativistic backward wave oscillator operating in TM02 with cutoff-type resonant reflector

NASA Astrophysics Data System (ADS)

Teng, Yan; Shi, Yanchao; Yang, Dewen; Cao, Yibing; Zhang, Zhijun

2017-04-01

This paper proposes an overmoded relativistic backward wave oscillator (RBWO) operating in the TM02 mode with the cutoff-type resonant reflector characterized by the advantages of the cutoff neck and the single resonant cavity. In order to protect the explosive emission of the annular cathode from the disturbance of the microwave leakage, the cutoff-type resonant reflector can effectively prevent the microwave consisting of several modes from propagating into the diode region. Attributed to the strong reflections caused by the cutoff-type resonant reflector at the front end of the overmoded slow-wave structure (SWS), the overmoded RBWO works in the state of the strong resonance, which enhances the beam-to-microwave power conversion efficiency. TM02 is selected as the operation mode so as to increase the power handling capability. The nonuniform SWS depresses the cross-excitation of the unwanted longitudinal modes of TM02 and improves the synchronous interaction between the electron beam and the structure wave. It is found that when we make the peak values of the longitudinal electric field and the modulated current appear nearly at the same position in the overmoded SWS by optimizing the electrodynamic structure, the conversion efficiency will be enhanced significantly. In the numerical simulation, the microwave generation with power 2.99 GW and efficiency 0.45 is obtained under the diode voltage 851 kV and current 7.8 kA with the guide magnetic field of 4.3 T. The microwave generation with the pure frequency spectrum of 10.083 GHz radiates in the TM01 mode. The conversion efficiency keeps above 0.40 over the diode voltage range of 220 kV.

A role for high frequency superconducting devices in free space power transmission systems

NASA Technical Reports Server (NTRS)

Christian, Jose L., Jr.; Cull, Ronald C.

1988-01-01

Major advances in space power technology are being made in photovoltaic, solar thermal, and nuclear systems. Despite these advances, the power systems required by the energy and power intensive mission of the future will be massive due to the large collecting surfaces, large thermal management systems, and heavy shielding. Reducing this mass on board the space vehicle can result in significant benefits because of the high cost of transporting and moving mass about in space. An approach to this problem is beaming the power from a point where the massiveness of the power plant is not such a major concern. The viability of such an approach was already investigated. Efficient microwave power beam transmission at 2.45 GHz was demonstrated over short range. Higher frequencies are desired for efficient transmission over several hundred or thousand kilometers in space. Superconducting DC-RF conversion as well as RF-DC conversion offers exciting possibilities. Multivoltage power conditioning for multicavity high power RF tubes could be eliminated since only low voltages are required for Josephson junctions. Small, high efficiency receivers may be possible using the reverse Josephson effects. A conceptual receiving antenna design using superconducting devices to determine possible system operating efficiency is assessed. If realized, these preliminary assessments indicate a role for superconducting devices in millimeter and submillimeter free space power transmission systems.

Diode-pumped laser altimeter

NASA Technical Reports Server (NTRS)

Welford, D.; Isyanova, Y.

1993-01-01

TEM(sub 00)-mode output energies up to 22.5 mJ with 23 percent slope efficiencies were generated at 1.064 microns in a diode-laser pumped Nd:YAG laser using a transverse-pumping geometry. 1.32-micron performance was equally impressive at 10.2 mJ output energy with 15 percent slope efficiency. The same pumping geometry was successfully carried forward to several complex Q-switched laser resonator designs with no noticeable degradation of beam quality. Output beam profiles were consistently shown to have greater than 90 percent correlation with the ideal TEM(sub 00)-order Gaussian profile. A comparison study on pulse-reflection-mode (PRM), pulse-transmission-mode (PTM), and passive Q-switching techniques was undertaken. The PRM Q-switched laser generated 8.3 mJ pulses with durations as short as 10 ns. The PTM Q-switch laser generated 5 mJ pulses with durations as short as 5 ns. The passively Q-switched laser generated 5 mJ pulses with durations as short as 2.4 ns. Frequency doubling of both 1.064 microns and 1.32 microns with conversion efficiencies of 56 percent in lithium triborate and 10 percent in rubidium titanyl arsenate, respectively, was shown. Sum-frequency generation of the 1.064 microns and 1.32 microns radiations was demonstrated in KTP to generate 1.1 mJ of 0.589 micron output with 11.5 percent conversion efficiency.

p-polarized Cherenkov THz wave radiation generated by optical rectification for a Brewster-cut LiNbO3 crystal

NASA Astrophysics Data System (ADS)

Liu, Pengxiang; Xu, Degang; Liu, Changming; Lv, Da; Lv, Yingjin; Wang, Peng; Yao, Jianquan

2011-08-01

In this paper, we investigated p-polarized Cherenkov radiation excited by an ultra-short laser pulse focused into a line in an LiNbO3 crystal. The geometries of p- and s-polarized THz generation were both analyzed. We did further calculations on p-polarized THz radiation and designed a Brewster-cut geometry. The radiated energy and conversion efficiency were roughly estimated. Compared with s-polarized waves radiated from a Cherenkov-cut crystal, p-polarized THz radiation has lower energy and conversion efficiency, but higher intensity and better beam quality. The effect of angular dispersion between the spectral components of the THz pulse after refraction at the Brewster surface was also discussed.

Nonlinear frequency doubling characteristics of asymmetric vortices of tunable, broad orbital angular momentum spectrum

NASA Astrophysics Data System (ADS)

Alam, Sabir Ul; Rao, A. Srinivasa; Ghosh, Anirban; Vaity, Pravin; Samanta, G. K.

2018-04-01

We report on a simple experimental scheme to generate and control the orbital angular momentum (OAM) spectrum of the asymmetric vortex beams in a nonlinear frequency conversion process. Using a spiral phase plate (SPP) and adjusting the transverse shift of the SPP with respect to the incident Gaussian beam axis, we have transformed the symmetric (intensity distribution) optical vortex of order l into an asymmetric vortex beam of measured broad spectrum of OAM modes of orders l, l - 1, l - 2, …, 0 (Gaussian mode). While the position of the SPP determines the distribution of the OAM modes, we have also observed that the modal distribution of the vortex beam changes with the shift of the SPP of all orders and finally results in a Gaussian beam (l = 0). Using single-pass frequency doubling of the asymmetric vortices, we have transferred the pump OAM spectra, l, l - 1, l - 2, …, 0, into the broad spectra of higher order OAM modes, 2l, 2l - 1, 2l - 2, …, 0 at green wavelength, owing to OAM conservation in nonlinear processes. We also observed an increase in single-pass conversion efficiency with the increase in asymmetry of the pump vortices producing a higher power vortex beam of mixed OAM modes at a new wavelength than that of the pure OAM mode.

A high-gain and high-efficiency X-band triaxial klystron amplifier with two-stage cascaded bunching cavities

NASA Astrophysics Data System (ADS)

Zhang, Wei; Ju, Jinchuan; Zhang, Jun; Zhong, Huihuang

2017-12-01

To achieve GW-level amplification output radiation at the X-band, a relativistic triaxial klystron amplifier with two-stage cascaded double-gap bunching cavities is investigated. The input cavity is optimized to obtain a high absorption rate of the external injection microwave. The cascaded bunching cavities are optimized to achieve a high depth of the fundamental harmonic current. A double-gap standing wave extractor is designed to improve the beam wave conversion efficiency. Two reflectors with high reflection coefficients both to the asymmetric mode and the TEM mode are employed to suppress the asymmetric mode competition and TEM mode microwave leakage. Particle-in-cell simulation results show that a high power microwave with a power of 2.53 GW and a frequency of 8.4 GHz is generated with a 690 kV, 9.3 kA electron beam excitation and a 25 kW seed microwave injection. Particularly, the achieved power conversion efficiency is about 40%, and the gain is as high as 50 dB. Meanwhile, there is insignificant self-excitation of the parasitic mode in the proposed structure by adopting the reflectors. The relative phase difference between the injected signals and the output microwaves keeps locked after the amplifier becomes saturated.

Modeling of high efficiency solar cells under laser pulse for power beaming applications

NASA Technical Reports Server (NTRS)

Jain, Raj K.; Landis, Geoffrey A.

1994-01-01

Solar cells have been used to convert sunlight to electrical energy for many years and also offer great potential for non-solar energy conversion applications. Their greatly improved performance under monochromatic light compared to sunlight, makes them suitable as photovoltaic (PV) receivers in laser power beaming applications. Laser beamed power to a PV array receiver could provide power to satellites, an orbital transfer vehicle, or a lunar base. Gallium arsenide (GaAs) and indium phosphide (InP) solar cells have calculated efficiencies of more than 50 percent under continuous illumination at the optimum wavelength. Currently high power free-electron lasers are being developed which operate in pulsed conditions. Understanding cell behavior under a laser pulse is important in the selection of the solar cell material and the laser. An experiment by NAsA lewis and JPL at the AVLIS laser facility in Livermore, CA presented experimental data on cell performance under pulsed laser illumination. Reference 5 contains an overview of technical issues concerning the use of solar cells for laser power conversion, written before the experiments were performed. As the experimental results showed, the actual effects of pulsed operation are more complicated. Reference 6 discusses simulations of the output of GaAs concentrator solar cells under pulsed laser illumination. The present paper continues this work, and compares the output of Si and GaAs solar cells.

Improvement of efficiency in graphene/gallium nitride nanowire on Silicon photoelectrode for overall water splitting

NASA Astrophysics Data System (ADS)

Bae, Hyojung; Rho, Hokyun; Min, Jung-Wook; Lee, Yong-Tak; Lee, Sang Hyun; Fujii, Katsushi; Lee, Hyo-Jong; Ha, Jun-Seok

2017-11-01

Gallium nitride (GaN) nanowires are one of the most promising photoelectrode materials due to their high stability in acidic and basic electrolytes, and tunable band edge potentials. In this study, GaN nanowire arrays (GaN NWs) were prepared by molecular beam epitaxy (MBE); their large surface area enhanced the solar to hydrogen conversion efficiency. More significantly, graphene was grown by chemical vapor deposition (CVD), which enhanced the electron transfer between NWs for water splitting and protected the GaN NW surface. Structural characterizations of the prepared composite were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocurrent density of Gr/GaN NWs exhibited a two-fold increase over pristine GaN NWs and sustained water splitting up to 70 min. These improvements may accelerate possible applications for hydrogen generation with high solar to hydrogen conversion efficiency.

Enhancement of quasi-static strain energy harvesters using non-uniform cross-section post-buckled beams

NASA Astrophysics Data System (ADS)

Jiao, Pengcheng; Borchani, Wassim; Hasni, Hassene; Lajnef, Nizar

2017-08-01

Thanks to their efficiency enhancement systems based on post-buckled structural elements have been extensively used in many applications such as actuation, remote sensing and energy harvesting. The post-buckling snap-through behavior of bilaterally constrained beams has been exploited to create sensing or energy harvesting mechanisms for quasi-static applications. The conversion mechanism has been used to transform low-rate and low-frequency excitations into high-rate motions. Electric energy has been generated from such high-rate motions using piezoelectric transducers. However, lack of control over the post-buckling behavior severely limits the mechanism’s efficiency. This study aims to maximize the levels of harvestable power by controlling the location of snap-throughs along the beam at different buckling transitions. Since the snap-through location cannot be controlled by tuning the geometric properties of a uniform beam, non-uniform cross-sections are examined. An energy-based theoretical model is herein developed to predict the post-buckling response of non-prismatic beams. The total potential energy is minimized under constraints that represent the physical confinement of the beam between the lateral boundaries. The experimentally validated results show that changing the shape and geometric dimensions of non-uniform beams allows for the accurate controlling of the snap-through location at different buckling transitions. A 78.59% improvement in harvested energy levels has been achieved by optimization of beam shape.

980 nm tapered lasers with photonic crystal structure for low vertical divergence

NASA Astrophysics Data System (ADS)

Ma, Xiaolong; Qu, Hongwei; Zhao, Pengchao; Liu, Yun; Zheng, Wanhua

2016-10-01

High power tapered lasers with nearly diffraction-limited beam quality have attracted much attention in numerous applications such as nonlinear frequency conversion, optical pumping of solid-state and fiber lasers, medical treatment and others. However, the large vertical divergence of conventional tapered lasers is a disadvantage, which makes beam shaping difficult and expensive in applications. Diode lasers with photonic crystal structure can achieve a large mode size and a narrow vertical divergence. In this paper, we present tapered lasers with photonic crystal structure emitting at 980 nm. The epitaxial layer is grown using metal organic chemical vapor deposition. The device has a total cavity length of 2 mm, which consists of a 400-um long ridge-waveguide section and a 1600-um long tapered section. The taper angle is 4°. An output power of 3.3 W is achieved with a peak conversion efficiency of 35% in pulsed mode. The threshold current is 240 mA and the slope efficiency is 0.78 W/A. In continuous wave mode, the output power is 2.87 W, which is limited by a suddenly failure resulting from catastrophic optical mirror damage. The far field divergences with full width at half maximum are 12.3° in the vertical direction and 2.9° in the lateral direction at 0.5 A. At high injection level the vertical divergence doesn't exceed 16°. Beam quality factor M2 is measured based on second moment definition in CW mode. High beam quality is demonstrated by M2 value of less than 2 in both vertical and lateral directions.

Wireless Power Transmission Technology State-Of-The-Art

NASA Astrophysics Data System (ADS)

Dickinson, R. M. T.

2002-01-01

This first Bill Brown SSP La Crescenta, CA 91214 technology , including microwave and laser systems for the transfer of electric , as related to eventually developing Space Solar Power (SSP) systems. Current and past technology accomplishments in ground based and air and space applied energy conversion devices, systems and modeling performance and cost information is presented, where such data are known to the author. The purpose of the presentation is to discuss and present data to encourage documenting and breaking the current technology records, so as to advance the SOA in WPT for SSP . For example, regarding DC to RF and laser converters, 83% efficient 2.45 GHz cooker-tube magnetrons with 800W CW output have been jointly developed by Russia and US. Over 50% wa11-plug efficient 1.5 kW/cm2 CW, water cooled, multibeam, solid state laser diode bar-arrays have been developed by LLNL at 808 nm wavelength. The Gennans have developed a 36% efficient, kW level, sing1e coherent beam, lateral pumped semiconductor laser. The record for end-to-end DC input to DC output power overall WPT link conversion efficiency is 54% during the Raytheon-JPL experiments in 1975 for 495.6 W recovered at 1.7-mrange at 2.4469 GAz. The record for usefully recovered electric power output ( as contrasted with thennally induced power in structures) is 34 kW OC output at a range of 1.55 km, using 2.388 GHz microwaves, during the JPL- Raytheon experiments by Bill Brown and the author at Goldstone, CA in 1975. The GaAs-diode rectenna array had an average collection-conversion efficiency of 82.5%. A single rectenna element operating a 6W RF input, developed by Bill Brown demonstrated 91.4% efficiency. The comparable record for laser light to OC output power conversion efficiency of photovoltaics is 590/0. for AlGaAs at 1.7 Wand 826nm wavelength. Russian cyclotron-wave converters have demonstrated 80% rectification efficiency at S-band. Concerning WPT technology equipment costs, magnetron conversion devices for microwave ovens are approximately O.O25/W, due to the large manufacturing quantities. Comparable, remanufactured lasers for industrial applications at the 4 kW CW level are of order 25/W. Industrial klystrons cost over 1/W and solid state power amplifiers cost over 3/W. Model tethered helicopters, model airplanes, a smal1 airship and several small rovers have been powered with microwave beams at 2.45, 5.8 and 35 GHz. Smal1 rovers have been powered with laser beams. Two space-to-space microwave power link experiments have been conducted by the Japanese and with Texas A&M assistance in one case. International records for WPT link electric power delivered, range, 1ink efficiency and other salient parameters for both wireless-laser and -microwave power demonstrations win be reviewed. Also, costing models for WPT -system figure- of-merit (FOM) in terms of capital costs, in /MW -km, as a fonction of range and power level are reviewed. Records in Japan. France, Korea, Russia, Canada and the US will be reviewed for various land based WPT demonstrations. SSP applicable elements of technology in fiber and wireless links, cell phones and base stations, aircraft, and spacecraft phased arrays, industrial and scientific klystrons and lasers, military equipment (where information is available in open literature) microwave heating, and other telecommunication activities win be presented, concerning power handling, frequency or wavelength, conversion efficiency, specific mass, specific cost, etc. Previously studied and proposed applications of WPT technology will be presented to show the range of WPT technology being considered for commercial and other applications that will lead to advancing the SOA of WPT technology that win benefit SSP .

Regimes of enhanced electromagnetic emission in beam-plasma interactions

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

Timofeev, I. V.; Annenkov, V. V.; Arzhannikov, A. V.

2015-11-15

The ways to improve the efficiency of electromagnetic waves generation in laboratory experiments with high-current relativistic electron beams injected into a magnetized plasma are discussed. It is known that such a beam can lose, in a plasma, a significant part of its energy by exciting a high level of turbulence and heating plasma electrons. Beam-excited plasma oscillations may simultaneously participate in nonlinear processes resulting in a fundamental and second harmonic emissions. It is obvious, however, that in the developed plasma turbulence the role of these emissions in the total energy balance is always negligible. In this paper, we investigate whethermore » electromagnetic radiation generated in the beam-plasma system can be sufficiently enhanced by the direct linear conversion of resonant beam-driven modes into electromagnetic ones on preformed regular inhomogeneities of plasma density. Due to the high power of relativistic electron beams, the mechanism discussed may become the basis for the generator of powerful sub-terahertz radiation.« less

Investigation of the summation of copper-vapour laser frequencies

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

Karpukhin, Vyacheslav T; Konev, Yu B; Malikov, Mikhail M

1998-09-30

An investigation was made of the conversion of the copper-vapour laser radiation ( {lambda}{sub 1} = 0.51 {mu}m and {lambda}{sub 2} = 0.578 {mu}m) into UV radiation at the sum frequency ({lambda}{sub 3} = 0.271 {mu}m) in a DKDP crystal. The operation of this frequency converter was compared for two magnifications of the laser cavity: M = 5 and 200. The best results were obtained for M = 200 (average UV radiation power 0.75 W, conversion efficiency 12%). A study was made of the characteristics of the formation of radiation pulses representing the two lines in the laser beam asmore » a whole and in its weakly diverging core. In a low-divergence beam the yellow- and green-line pulses were emitted practically simultaneously with approximately the same peak power, which facilitated the sum-frequency generation. (nonlinear optical phenomena)« less

7.5 W blue light generation at 452 nm by internal frequency doubling of a continuous-wave Nd-doped fiber laser.

PubMed

Leconte, Baptiste; Gilles, Hervé; Robin, Thierry; Cadier, Benoit; Laroche, Mathieu

2018-04-16

We present the first frequency-doubled neodymium-doped fiber laser generating multi-watt CW power near 450 nm. A bow-tie resonator incorporating a LBO nonlinear crystal is integrated within a Nd-doped fiber laser emitting near 900 nm. This scheme achieves an IR to blue conversion efficiency close to 55% without any active control of the internal resonant cavity. As a result, up to 7.5 W of linearly-polarized blue power is generated, with beam quality factors M x 2 ~1.0 and M y 2 ~1.5. A simple numerical model has been developed to optimize and analyse the IR to blue conversion efficiency in the resonant cavity. Performance limitations and prospects for further improvements are discussed.

Optical Amplifier Based Space Solar Power

NASA Technical Reports Server (NTRS)

Fork, Richard L.

2001-01-01

The objective was to design a safe optical power beaming system for use in space. Research was focused on identification of strategies and structures that would enable achievement near diffraction limited optical beam quality, highly efficient electrical to optical conversion, and high average power in combination in a single system. Efforts centered on producing high efficiency, low mass of the overall system, low operating temperature, precision pointing and tracking capability, compatibility with useful satellite orbits, component and system reliability, and long component and system life in space. A system based on increasing the power handled by each individual module to an optimum and the number of modules in the complete structure was planned. We were concerned with identifying the most economical and rapid path to commercially viable safe space solar power.

High efficiency compound semiconductor concentrator photovoltaics

NASA Technical Reports Server (NTRS)

Borden, P.; Gregory, P.; Saxena, R.; Owen, R.; Moore, O.

1980-01-01

Special emphasis was given to the high yield pilot production of packaged AlGaAs/GaAs concentrator solar cells, using organometallic VPE for materials growth, the demonstration of a concentrator module using 12 of these cells which achieved 16.4 percent conversion efficiency at 50 C coolant inlet temperature, and the demonstration of a spectral splitting converter module that achieved in excess of 20 percent efficiency. This converter employed ten silicon and ten AlGaAs cells with a dichroic filter functioning as the beam splitter. A monolithic array of AlGaAs/GaAs solar cells is described.

The first measurements of soft x-ray flux from ignition scale Hohlraums at the national ignition facility using DANTE

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

Kline, John L; Glenzer, S H; Olson, Rick

2010-01-01

The first 96 and 192 beam vacuum hohlraum have been fielded at the National Ignition Facility demonstrating radiation temperatures up to 340 eV and fluxes of 20 TW/sr representing a 20 times flux increase over NOVA/Omega scale hohlraums. The vacuum hohlraums were irradiated with 2 ns square pulses with energies between 150 - 635 kJ. They produced nearly Planckian spectra with about 30 {+-} 10% more flux than predicted by the current radiation hydrodynamic simulations after careful verification of all component calibrations (which included an {approx} 10% downward correction to Center X-Ray Optics opacities just below the Cu L edgemore » at 50-750 eV), cable deconvolution, and analysis software routines. To corroborate these results, first a half hohlraum experiment was conducted using a single 2 ns-long axial quad with an irradiance of {approx} 1-2 x 10{sup 15} W/cm{sup 2} for comparison with NIF Early Light experiments completed in 2004. Second, we completed a conversion efficiency test using a 128-beam nearly uniformly illuminated gold sphere with intensities kept low (at 1 x 10{sup 14} W/cm{sup 2} over 5 ns) to avoid sensitivity to modeling uncertainties for non-local heat conduction and non-linear absorption mechanisms, to compare with similar intensity, 3 ns OMEGA sphere results. The 2004 and 2009 NIF half-hohlraums agreed to 10% in flux, but more importantly, the 2006 OMEGA Au Sphere, the 2009 NIF Au sphere and the calculated Au conversion efficiency agree to {+-}5% in flux, which is estimated to be the absolute calibration accuracy of the DANTEs. Hence we concluded the 30 {+-} 10% higher than expected radiation fluxes from the 96 and 192 beam vacuum hohlraums are attributable to differences in physics when we transitioned to large hot hohlraums. Specifically, using variants in the atomic physics models and electron heat conduction, newer simulations show that nonlocalization of energy deposition leads to less energy being stored in the coronal plasma leading to higher x-ray conversion efficiency. Since the larger volume-to-area ratio hohlraums have large coronal plasmas which scale volumetrically, the reduction in energy losses to the corona become more pronounced than for smaller NOVA/Omega scale hohlraums. The higher conversion efficiencies are also consistent with observations from other 1 ns gold sphere experiments conducted at Omega with 1 x 10{sup 15} W/cm{sup 2} laser irradiances.« less

Gamma beams generation with high intensity lasers for two photon Breit-Wheeler pair production

NASA Astrophysics Data System (ADS)

D'Humieres, Emmanuel; Ribeyre, Xavier; Jansen, Oliver; Esnault, Leo; Jequier, Sophie; Dubois, Jean-Luc; Hulin, Sebastien; Tikhonchuk, Vladimir; Arefiev, Alex; Toncian, Toma; Sentoku, Yasuhiko

2017-10-01

Linear Breit-Wheeler pair creation is the lowest threshold process in photon-photon interaction, controlling the energy release in Gamma Ray Bursts and Active Galactic Nuclei, but it has never been directly observed in the laboratory. Using numerical simulations, we demonstrate the possibility to produce collimated gamma beams with high energy conversion efficiency using high intensity lasers and innovative targets. When two of these beams collide at particular angles, our analytical calculations demonstrate a beaming effect easing the detection of the pairs in the laboratory. This effect has been confirmed in photon collision simulations using a recently developed innovative algorithm. An alternative scheme using Bremsstrahlung radiation produced by next generation high repetition rate laser systems is also being explored and the results of first optimization campaigns in this regime will be presented.

Advanced Energy Conversion Technologies and Architectures for Earth and Beyond

NASA Technical Reports Server (NTRS)

Howell, Joe T.; Fikes, John C.; Phillips, Dane J.; Laycock, Rustin L.; ONeill, Mark; Henley, Mark W.; Fork, Richard L.

2006-01-01

Research, development and studies of novel space-based solar power systems, technologies and architectures for Earth and beyond are needed to reduce the cost of clean electrical power for terrestrial use and to provide a stepping stone for providing an abundance of power in space, i.e., manufacturing facilities, tourist facilities, delivery of power between objects in space, and between space and surface sites. The architectures, technologies and systems needed for space to Earth applications may also be used for in-space applications. Advances in key technologies, i.e., power generation, power management and distribution, power beaming and conversion of beamed power are needed to achieve the objectives of both terrestrial and extraterrestrial applications. There is a need to produce "proof-ofconcept" validation of critical WPT technologies for both the near-term, as well as far-term applications. Investments may be harvested in near-term beam safe demonstrations of commercial WPT applications. Receiving sites (users) include ground-based stations for terrestrial electrical power, orbital sites to provide power for satellites and other platforms, future space elevator systems, space vehicle propulsion, and space surface sites. Space surface receiving sites of particular interest include the areas of permanent shadow near the moon s North and South poles, where WPT technologies could enable access to ice and other useful resources for human exploration. This paper discusses work addressing a promising approach to solar power generation and beamed power conversion. The approach is based on a unique high-power solar concentrator array called Stretched Lens Array (SLA) applied to both solar power generation and beamed power conversion. Since both versions (solar and laser) of SLA use many identical components (only the photovoltaic cells need to be different), economies of manufacturing and scale may be realized by using SLA on both ends of the laser power beaming system in a space solar power application. Near-term uses of this SLA-laser-SLA system may include terrestrial and space exploration in near Earth space. Later uses may include beamed power for bases or vehicles on Mars. Strategies for developing energy infrastructures in space which utilize this technology are presented. This dual use system produces electrical energy efficiently from either coherent light, such as from a highly coherent laser, or from conventional solar illumination. This allows, for example, supplementing solar energy with energy provided by highly coherent laser illumination during periods of low solar illumination or no illumination. This reduces the need for batteries and alternate sources of power. The capability of using laser illumination in a lowest order Gaussian laser mode provides means for transmitting power optically with maximum efficiency and precision over the long distances characteristic of space. A preliminary receiving system similar to that described here, has been produced and tested under solar and laser illumination. A summary of results is given.

Novel Space-based Solar Power Technologies and Architectures for Earth and Beyond

NASA Technical Reports Server (NTRS)

Howell, Joe T.; Fikes, John C.; O'Neill, Mark J.

2005-01-01

Research, development and studies of novel space-based solar power systems, technologies and architectures for Earth and beyond are needed to reduce the cost of clean electrical power for terrestrial use and to provide a stepping stone for providing an abundance of power in space, i.e., manufacturing facilities, tourist facilities, delivery of power between objects in space, and between space and surface sites. The architectures, technologies and systems needed for space to Earth applications may also be used for in-space applications. Advances in key technologies, i.e., power generation, power management and distribution, power beaming and conversion of beamed power are needed to achieve the objectives of both terrestrial and extraterrestrial applications. Power beaming or wireless power transmission (WPT) can involve lasers or microwaves along with the associated power interfaces. Microwave and laser transmission techniques have been studied with several promising approaches to safe and efficient WPT identified. These investigations have included microwave phased array transmitters, as well as laser transmission and associated optics. There is a need to produce "proof-of-concept" validation of critical WPT technologies for both the near-term, as well as far-term applications. Investments may be harvested in near-term beam safe demonstrations of commercial WPT applications. Receiving sites (users) include ground-based stations for terrestrial electrical power, orbital sites to provide power for satellites and other platforms, future space elevator systems, space vehicle propulsion, and space to surface sites. This paper briefly discusses achieving a promising approach to the solar power generation and beamed power conversion. The approach is based on a unique high-power solar concentrator array called Stretched Lens Array (SLA) for both solar power generation and beamed power conversion. Since both versions (solar and laser) of SLA use many identical components (only the photovoltaic cells need to be different), economies of manufacturing and scale may be realized by using SLA on both ends of the laser power beaming system in a space solar power application. Near-term uses of this SLA-laser-SLA system may include terrestrial and space exploration in near Earth space. Later uses may include beamed power for bases or vehicles on Mars.

Beam conditioner for free electron lasers and synchrotrons

DOEpatents

Liu, H.; Neil, G.R.

1998-09-08

A focused optical has been used to introduce an optical pulse, or electromagnetic wave, collinear with the electron beam in a free electron laser or synchrotron thereby adding an axial field component that accelerates the electrons on the radial outside of the distribution of electrons in the electron beam. This invention consists of using the axial electrical component of a TEM{sub 10} mode Gaussian beam in vacuum to condition the electron beam and speed up the outer electrons in the beam. The conditioning beam should possess about the same diameter as the electron beam. The beam waist of the conditioning wave must be located around the entrance of the undulator longitudinally to have a net energy exchange between the electrons in the outer part of the distribution and the conditioning wave owing to the natural divergence of a Gaussian beam. By accelerating the outer electrons, the outer and core electrons are caused to stay in phase. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron. 4 figs.

Beam conditioner for free electron lasers and synchrotrons

DOEpatents

Liu, Hongxiu; Neil, George R.

1998-01-01

A focused optical is been used to introduce an optical pulse, or electromagnetic wave, colinearly with the electron beam in a free electron laser or synchrotron thereby adding an axial field component that accelerates the electrons on the radial outside of the distribution of electrons in the electron beam. This invention consists of using the axial electrical component of a TEM.sub.10 mode Gaussian beam in vacuum to condition the electron beam and speed up the outer electrons in the beam. The conditioning beam should possess about the same diameter as the electron beam. The beam waist of the conditioning wave must be located around the entrance of the undulator longitudinally to have a net energy exchange between the electrons in the outer part of the distribution and the conditioning wave owing to the natural divergence of a Gaussian beam. By accelerating the outer electrons, the outer and core electrons are caused to stay in phase. This increases the fraction of the electron beam energy that is converted to light thereby improving the efficiency of conversion of energy to light and therefore boosting the power output of the free electron laser and synchrotron.

Numerical investigation of a scalable setup for efficient terahertz generation using a segmented tilted-pulse-front excitation.

PubMed

Pálfalvi, László; Tóth, György; Tokodi, Levente; Márton, Zsuzsanna; Fülöp, József András; Almási, Gábor; Hebling, János

2017-11-27

A hybrid-type terahertz pulse source is proposed for high energy terahertz pulse generation. It is the combination of the conventional tilted-pulse-front setup and a transmission stair-step echelon-faced nonlinear crystal with a period falling in the hundred-micrometer range. The most important advantage of the setup is the possibility of using plane parallel nonlinear optical crystal for producing good-quality, symmetric terahertz beam. Another advantage of the proposed setup is the significant reduction of imaging errors, which is important in the case of wide pump beams that are used in high energy experiments. A one dimensional model was developed for determining the terahertz generation efficiency, and it was used for quantitative comparison between the proposed new hybrid setup and previously introduced terahertz sources. With lithium niobate nonlinear material, calculations predict an approximately ten-fold increase in the efficiency of the presently described hybrid terahertz pulse source with respect to that of the earlier proposed setup, which utilizes a reflective stair-step echelon and a prism shaped nonlinear optical crystal. By using pump pulses of 50 mJ pulse energy, 500 fs pulse length and 8 mm beam spot radius, approximately 1% conversion efficiency and 0.5 mJ terahertz pulse energy can be reached with the newly proposed setup.

High-efficiency V-band GaAs IMPATT diodes

NASA Technical Reports Server (NTRS)

Ma, Y. E.; Benko, E.; Trinh, T.; Erickson, L. P.; Mattord, T. J.

1984-01-01

Double-drift GaAs IMPATT diodes were designed for V-band frequency operations and fabricated using molecular-beam epitaxy. The diodes were fabricated in two configurations: (1) circular mesa diodes with silver-plated (integrated) heat sinks: (2) pill-type diodes bonded to diamond heat sinks. Both configurations utilized a miniature quartz-ring package. Output power greater than 1 W CW was achieved at V-band frequencies from diodes on diamond heat sinks. The best conversion efficiency was 13.3 percent at 55.5 GHz with 1 W output power.

Advanced Rainbow Solar Photovoltaic Arrays

NASA Technical Reports Server (NTRS)

Mardesich, Nick; Shields, Virgil

2003-01-01

Photovoltaic arrays of the rainbow type, equipped with light-concentrator and spectral-beam-splitter optics, have been investigated in a continuing effort to develop lightweight, high-efficiency solar electric power sources. This investigation has contributed to a revival of the concept of the rainbow photovoltaic array, which originated in the 1950s but proved unrealistic at that time because the selection of solar photovoltaic cells was too limited. Advances in the art of photovoltaic cells since that time have rendered the concept more realistic, thereby prompting the present development effort. A rainbow photovoltaic array comprises side-by-side strings of series-connected photovoltaic cells. The cells in each string have the same bandgap, which differs from the bandgaps of the other strings. Hence, each string operates most efficiently in a unique wavelength band determined by its bandgap. To obtain maximum energy-conversion efficiency and to minimize the size and weight of the array for a given sunlight input aperture, the sunlight incident on the aperture is concentrated, then spectrally dispersed onto the photovoltaic array plane, whereon each string of cells is positioned to intercept the light in its wavelength band of most efficient operation. The number of cells in each string is chosen so that the output potentials of all the strings are the same; this makes it possible to connect the strings together in parallel to maximize the output current of the array. According to the original rainbow photovoltaic concept, the concentrated sunlight was to be split into multiple beams by use of an array of dichroic filters designed so that each beam would contain light in one of the desired wavelength bands. The concept has since been modified to provide for dispersion of the spectrum by use of adjacent prisms. A proposal for an advanced version calls for a unitary concentrator/ spectral-beam-splitter optic in the form of a parabolic curved Fresnel-like prism array with panels of photovoltaic cells on two sides (see figure). The surface supporting the solar cells can be adjusted in length or angle to accommodate the incident spectral pattern. An unoptimized prototype assembly containing ten adjacent prisms and three photovoltaic cells with different bandgaps (InGaP2, GaAs, and InGaAs) was constructed to demonstrate feasibility. The actual array will consist of a lightweight thin-film silicon layer of prisms curved into a parabolic shape. In an initial test under illumination of 1 sun at zero airmass, the energy-conversion efficiency of the assembly was found to be 20 percent. Further analysis of the data from this test led to a projected energy conversion efficiency as high as 41 percent for an array of 6 cells or strings (GaP, AlGaAs, InGaP2, GaAs, and two different InGaAs cells or strings).

Magnetic Carbon nanoparticles enabled efficient photothermal alteration of mammalian cells

NASA Astrophysics Data System (ADS)

Cardenas, Nelson; Thomas, Patrick; Yu, Lingfeng; Mohanty, Samarendra

2011-03-01

While cw near-infrared (NIR) laser beams have been finding widespread application in photothermal therapy of cancer and pulsed NIR laser microbeams are recently being used for optoporation of exogeneous impermeable materials into cells. Since, carbon nanomaterials are very good in photothermal conversion, we utilized carbon nanoparticles (CNP) doped with Fe, so that they can be localized in a defined area by two fold selectivity, (i) external magnetic field for retention of the CNP in targeted area and (ii) surface functionalization for binding the targeted cells. Here, we report efficient photothermal therapy as well as poration of cells using magnetic CNPs with very low power continuous wave laser beam. Localization of CNPs on cell membrane under application of magnetic field was confirmed by scanning electron microscopy. At different power levels, cells could be damaged or microinjected with fluorescence protein-encoding plasmids or impermeable dyes. Monte Carlo simulation showed that the dose of NIR laser beam is sufficient to elicit response for magnetic CNP based photothermal treatment at significant depth. The results of our study suggest that magnetic CNP based photothermal alteration is a viable approach to remotely guide treatments offering high efficiency with significantly reduced cytotoxicity.

Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media

NASA Astrophysics Data System (ADS)

Vezzoli, Stefano; Bruno, Vincenzo; DeVault, Clayton; Roger, Thomas; Shalaev, Vladimir M.; Boltasseva, Alexandra; Ferrera, Marcello; Clerici, Matteo; Dubietis, Audrius; Faccio, Daniele

2018-01-01

Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008), 10.1126/science.1162087]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.

Infrared chemiluminescence study of the reaction Cl + HI yielding HCl + I at enhanced collision energies.

NASA Technical Reports Server (NTRS)

Cowley, L. T.; Horne, D. S.; Polanyi, J. C.

1971-01-01

Performed chemiluminescence and beam experiments show a markedly increased efficiency of conversion of the reaction energy into vibration and a markedly enhanced tendency for forward scattering in the reaction Cl + HI yields HCl + I as compared with H + Cl2 yields HCl + Cl. These differences appear to be due predominantly to the difference in the masses involved.

High-power narrow-linewidth quasi-CW diode-pumped TEM00 1064 nm Nd:YAG ring laser.

PubMed

Liu, Yuan; Wang, Bao-shan; Xie, Shi-yong; Bo, Yong; Wang, Peng-yuan; Zuo, Jun-wei; Xu, Yi-ting; Xu, Jia-lin; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

2012-04-01

We demonstrated a high average power, narrow-linewidth, quasi-CW diode-pumped Nd:YAG 1064 nm laser with near-diffraction-limited beam quality. A symmetrical three-mirror ring cavity with unidirectional operation elements and an etalon was employed to realize the narrow-linewidth laser output. Two highly efficient laser modules and a 90° quartz rotator for birefringence compensation were used for the high output power. The maximum average output power of 62.5 W with the beam quality factor M(2) of 1.15 was achieved under a pump power of 216 W at a repetition rate of 500 Hz, corresponding to the optical-to-optical conversion efficiency of 28.9%. The linewidth of the laser at the maximum output power was measured to be less than 0.2 GHz.

High beam quality of a Q-switched 2-µm Tm,Ho:LuVO4 laser

NASA Astrophysics Data System (ADS)

Wang, Wei; Yang, Xining; Shen, Yingjie; Li, Linjun; Zhou, Long; Yang, Yuqiang; Bai, Yunfeng; Xie, Wenqiang; Ye, Guangchao; Yu, Xiaoyang

2018-05-01

A diode-end-pumped 2.05-µm Q-switched Tm,Ho:LuVO4 laser is reported in this paper. The cryogenic Tm3+ (5.0 at.%),Ho3+ (0.5 at.%):LuVO4 crystal was pumped by an 800-nm laser diode. At a pulse repetition frequency of 10 kHz, the maximum average output power of 3.77 W was achieved at 77 K when an incident pump power of 14.7 W was used. The slope efficiency and optical-optical conversion efficiency were 28.3 and 25.6%, respectively. The maximum per pulse energy was 2.54 mJ for a pulse duration of 69.9 ns. The beam quality factor Mx 2 was approximately 1.17 and My 2 was approximately 1.01 for the Tm,Ho:LuVO4 laser.

Preparation of reflective CsI photocathodes with reproducible high quantum efficiency

NASA Astrophysics Data System (ADS)

Maier-Komor, P.; Bauer, B. B.; Friese, J.; Gernhäuser, R.; Kienle, P.; Körner, H. J.; Montermann, G.; Zeitelhack, K.

1995-02-01

CsI as a solid UV-photocathode material has many promising applications in fast gaseous photon detectors. They are proposed in large area Ring Imaging CHerenkov (RICH) devices in forthcoming experiments at various high-energy particle accelerators. A high photon-to-electron conversion efficiency is a basic requirement for the successful operation of these devices. High reproducible quantum efficiencies could be achieved with CsI layers prepared by electron beam evaporation from a water-cooled copper crucible. CsI films were deposited in the thickness range of 30 to 500 μg/cm 2. Absorption coefficients and quantum efficiencies were measured in the wavelength region of 150 nm to 250 nm. The influence of various evaporation parameters on the quantum efficiency were investigated.

Second harmonic generation of q-Gaussian laser beam in preformed collisional plasma channel with nonlinear absorption

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

Gupta, Naveen, E-mail: naveens222@rediffmail.com; Singh, Arvinder, E-mail: arvinder6@lycos.com; Singh, Navpreet, E-mail: navpreet.nit@gmail.com

2015-11-15

This paper presents a scheme for second harmonic generation of an intense q-Gaussian laser beam in a preformed parabolic plasma channel, where collisional nonlinearity is operative with nonlinear absorption. Due to nonuniform irradiance of intensity along the wavefront of the laser beam, nonuniform Ohmic heating of plasma electrons takes place. Due to this nonuniform heating of plasma, the laser beam gets self-focused and produces strong density gradients in the transverse direction. The generated density gradients excite an electron plasma wave at pump frequency that interacts with the pump beam to produce its second harmonics. The formulation is based on amore » numerical solution of the nonlinear Schrodinger wave equation in WKB approximation followed by moment theory approach. A second order nonlinear differential equation governing the propagation dynamics of the laser beam with distance of propagation has been obtained and is solved numerically by Runge Kutta fourth order technique. The effect of nonlinear absorption on self-focusing of the laser beam and conversion efficiency of its second harmonics has been investigated.« less

Out-of-Time Beam Extinction in the MU2E Experiment

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

Prebys, E. J.; Werkema, S.

The Mu2e Experiment at Fermilab will search for the conversion of a muon to an electron in the field of an atomic nucleus with unprecedented sensitivity. The experiment requires a beam consisting of proton bunches 250 ns FW long, separated by 1.7more » $$\\mu$$ sec, with no out-of-time protons at the $$10^{10}$$ fractional level. Satisfying this "extinction" requirement is very challenging. The formation of the bunches is expected to result in an extinction on the order of $10^5$. The remaining extinction will be accomplished by a system of resonant magnets and collimators, configured such that only in-time beam is delivered to the experiment. Our simulations show that the total extinction achievable by the system is on the order of $$10^{12}$$, with an efficiency for transmitting in-time beam of 99.6%.« less

A high efficiency Ku-band radial line relativistic klystron amplifier

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

Dang, Fangchao; Zhang, Xiaoping, E-mail: zhangxiaoping@nudt.edu.cn; Zhong, Huihuang

2016-07-15

To achieve the gigawatt-level microwave amplification output at Ku-band, a radial-line relativistic klystron amplifier is proposed and investigated in this paper. Different from the annular electron beam in conventional axial relativistic klystron amplifiers, a radial-radiated electron beam is employed in this proposed klystron. Owing to its radially spreading speciality, the electron density and space charge effect are markedly weakened during the propagation in the radial line drift tube. Additionally, the power capacity, especially in the output cavity, is enhanced significantly because of its large volume, which is profitable for the long pulse operation. Particle-in-cell simulation results demonstrate that a highmore » power microwave with the power of 3 GW and the frequency of 14.25 GHz is generated with a 500 kV, 12 kA electron beam excitation and the 30 kW radio-frequency signal injection. The power conversion efficiency is 50%, and the gain is about 50 dB. Meanwhile, there is insignificant electron beam self-excitation in the proposed structure by the adoption of two transverse electromagnetic reflectors. The relative phase difference between the injected signals and output microwaves keeps stable after the amplifier saturates.« less

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

Shaw, B. H.; Applied Science and Technology, University of California, Berkeley, California 94720; Tilborg, J. van

Solid-based surface high-harmonic generation from a tape is experimentally studied. By operating at mildly relativistic normalized laser strengths a{sub 0}≲0.2, harmonics up to the 17th order are efficiently produced in the coherent wake emission (CWE) regime. CWE pulse properties, such as divergence, energy, conversion efficiency, and spectrum, are investigated for various tape materials and drive laser conditions. A clear correlation between surface roughness and harmonic beam divergence is found. At the measured pulse properties for the 15th harmonic (conversion efficiency ∼6.5×10{sup −7}, divergence ∼7−15 mrad), the 100-mJ-level drive laser produces several MWs of extreme ultra-violet pulses. The spooling tape configurationmore » enables multi-Hz operation over thousands of shots, making this source attractive as a seed to the few-Hz laser-plasma-accelerator-driven free-electron laser (FEL). Models indicate that these CWE pulses with MW level powers are sufficient for seed-induced bunching and FEL gain.« less

Sixty GHz IMPATT diode development

NASA Technical Reports Server (NTRS)

Ma, Y. E.; Chen, J.; Benko, E.; Barger, M. J.; Nghiem, H.; Trinh, T. Q.; Kung, J.

1985-01-01

The objective of this program is to develop 60 GHz GaAs IMPATT Diodes suitable for communications applications. The performance goal of the 60 GHz IMPATT is 1W CW output power with a conversion efficiency of 15 percent and 10 year life time. During the course of the program, double drift (DD) GaAs IMPATT Diodes have been developed resulting in the state of the art performance at V band frequencies. A CW output power of 1.12 W was demonstrated at 51.9 GHz with 9.7 percent efficiency. The best conversion efficiency achieved was 15.3 percent. V band DD GaAs IMPATTs were developed using both small signal and large signal analyses. GaAs wafers of DD flat, DD hybrid, and DD Read profiles using molecular beam epitaxy (MBE) were developed with excellent doping profile control. Wafer evaluation was routinely made by the capacitance versus voltage (C-V) measurement. Ion mass spectrometry (SIMS) analysis was also used for more detailed profile evaluation.

Infrared power cells for satellite power conversion

NASA Technical Reports Server (NTRS)

Summers, Christopher J.

1991-01-01

An analytical investigation is performed to assess the feasibility of long-wavelength power converters for the direct conversion of IR radiation onto electrical power. Because theses devices need to operate between 5 and 30 um the only material system possible for this application is the HgCdTe system which is currently being developed for IR detectors. Thus solar cell and IR detector theories and technologies are combined. The following subject areas are covered: electronic and optical properties of HgCdTe alloys; optimum device geometry; junction theory; model calculation for homojunction power cell efficiency; and calculation for HgCdTe power cell and power beaming.

Injection-insensitive lateral divergence in broad-area diode lasers achieved by spatial current modulation

NASA Astrophysics Data System (ADS)

Wang, Tao; Tong, Cunzhu; Wang, Lijie; Zeng, Yugang; Tian, Sicong; Shu, Shili; Zhang, Jian; Wang, Lijun

2016-11-01

High-power broad-area (BA) diode lasers often suffer from low beam quality, broad linewidth, and a widened slow-axis far field with increasing current. In this paper, a two-dimensional current-modulated structure is proposed and it is demonstrated that it can reduce not only the far-field sensitivity to the injection current but also the linewidth of the lasing spectra. Injection-insensitive lateral divergence was realized, and the beam parameter product (BPP) was improved by 36.5%. At the same time, the linewidth was decreased by about 45% without significant degradations of emission power and conversion efficiency.

Nonlinear analysis of a relativistic beam-plasma cyclotron instability

NASA Technical Reports Server (NTRS)

Sprangle, P.; Vlahos, L.

1986-01-01

A self-consistent set of nonlinear and relativistic wave-particle equations are derived for a magnetized beam-plasma system interacting with electromagnetic cyclotron waves. In particular, the high-frequency cyclotron mode interacting with a streaming and gyrating electron beam within a background plasma is considered in some detail. This interaction mode may possibly find application as a high-power source of coherent short-wavelength radiation for laboratory devices. The background plasma, although passive, plays a central role in this mechanism by modifying the dielectric properties in which the magnetized electron beam propagates. For a particular choice of the transverse beam velocity (i.e., the speed of light divided by the relativistic mass factor), the interaction frequency equals the nonrelativistic electron cyclotron frequency times the relativistic mass factor. For this choice of transverse beam velocity the detrimental effects of a longitudinal beam velocity spread is virtually removed. Power conversion efficiencies in excess of 18 percent are both analytically calculated and obtained through numerical simulations of the wave-particle equations. The quality of the electron beam, degree of energy and pitch angle spread, and its effect on the beam-plasma cyclotron instability is studied.

Efficient Second Harmonic Generation in 3D Nonlinear Optical-Lattice-Like Cladding Waveguide Splitters by Femtosecond Laser Inscription

PubMed Central

Nie, Weijie; Jia, Yuechen; Vázquez de Aldana, Javier R.; Chen, Feng

2016-01-01

Integrated photonic devices with beam splitting function are intriguing for a broad range of photonic applications. Through optical-lattice-like cladding waveguide structures fabricated by direct femtosecond laser writing, the light propagation can be engineered via the track-confined refractive index profiles, achieving tailored output beam distributions. In this work, we report on the fabrication of 3D laser-written optical-lattice-like structures in a nonlinear KTP crystal to implement 1 × 4 beam splitting. Second harmonic generation (SHG) of green light through these nonlinear waveguide beam splitter structures provides the capability for the compact visible laser emitting devices. With Type II phase matching of the fundamental wavelength (@ 1064 nm) to second harmonic waves (@ 532 nm), the frequency doubling has been achieved through this three-dimensional beam splitter. Under 1064-nm continuous-wave fundamental-wavelength pump beam, guided-wave SHG at 532 nm are measured with the maximum power of 0.65 mW and 0.48 mW for waveguide splitters (0.67 mW and 0.51 mW for corresponding straight channel waveguides), corresponding to a SH conversion efficiency of approximately ~14.3%/W and 13.9%/W (11.2%/W, 11.3%/W for corresponding straight channel waveguides), respectively. This work paves a way to fabricate compact integrated nonlinear photonic devices in a single chip with beam dividing functions. PMID:26924255

Efficient Second Harmonic Generation in 3D Nonlinear Optical-Lattice-Like Cladding Waveguide Splitters by Femtosecond Laser Inscription.

PubMed

Nie, Weijie; Jia, Yuechen; Vázquez de Aldana, Javier R; Chen, Feng

2016-02-29

Integrated photonic devices with beam splitting function are intriguing for a broad range of photonic applications. Through optical-lattice-like cladding waveguide structures fabricated by direct femtosecond laser writing, the light propagation can be engineered via the track-confined refractive index profiles, achieving tailored output beam distributions. In this work, we report on the fabrication of 3D laser-written optical-lattice-like structures in a nonlinear KTP crystal to implement 1 × 4 beam splitting. Second harmonic generation (SHG) of green light through these nonlinear waveguide beam splitter structures provides the capability for the compact visible laser emitting devices. With Type II phase matching of the fundamental wavelength (@ 1064 nm) to second harmonic waves (@ 532 nm), the frequency doubling has been achieved through this three-dimensional beam splitter. Under 1064-nm continuous-wave fundamental-wavelength pump beam, guided-wave SHG at 532 nm are measured with the maximum power of 0.65 mW and 0.48 mW for waveguide splitters (0.67 mW and 0.51 mW for corresponding straight channel waveguides), corresponding to a SH conversion efficiency of approximately ~14.3%/W and 13.9%/W (11.2%/W, 11.3%/W for corresponding straight channel waveguides), respectively. This work paves a way to fabricate compact integrated nonlinear photonic devices in a single chip with beam dividing functions.

High efficiency solar cells combining a perovskite and a silicon heterojunction solar cells via an optical splitting system

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

Uzu, Hisashi, E-mail: Hisashi.Uzu@kaneka.co.jp, E-mail: npark@skku.edu; Ichikawa, Mitsuru; Hino, Masashi

2015-01-05

We have applied an optical splitting system in order to achieve very high conversion efficiency for a full spectrum multi-junction solar cell. This system consists of multiple solar cells with different band gap optically coupled via an “optical splitter.” An optical splitter is a multi-layered beam splitter with very high reflection in the shorter-wave-length range and very high transmission in the longer-wave-length range. By splitting the incident solar spectrum and distributing it to each solar cell, the solar energy can be managed more efficiently. We have fabricated optical splitters and used them with a wide-gap amorphous silicon (a-Si) solar cellmore » or a CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cell as top cells, combined with mono-crystalline silicon heterojunction (HJ) solar cells as bottom cells. We have achieved with a 550 nm cutoff splitter an active area conversion efficiency of over 25% using a-Si and HJ solar cells and 28% using perovskite and HJ solar cells.« less

Efficient 2(nd) and 4(th) harmonic generation of a single-frequency, continuous-wave fiber amplifier.

PubMed

Sudmeyer, Thomas; Imai, Yutaka; Masuda, Hisashi; Eguchi, Naoya; Saito, Masaki; Kubota, Shigeo

2008-02-04

We demonstrate efficient cavity-enhanced second and fourth harmonic generation of an air-cooled, continuous-wave (cw), single-frequency 1064 nm fiber-amplifier system. The second harmonic generator achieves up to 88% total external conversion efficiency, generating more than 20-W power at 532 nm wavelength in a diffraction-limited beam (M(2) < 1.05). The nonlinear medium is a critically phase-matched, 20-mm long, anti-reflection (AR) coated LBO crystal operated at 25 degrees C. The fourth harmonic generator is based on an AR-coated, Czochralski-grown beta-BaB(2)O(4) (BBO) crystal optimized for low loss and high damage threshold. Up to 12.2 W of 266-nm deep-UV (DUV) output is obtained using a 6-mm long critically phase-matched BBO operated at 40 degrees C. This power level is more than two times higher than previously reported for cw 266-nm generation. The total external conversion efficiency from the fundamental at 1064 nm to the fourth harmonic at 266 nm is >50%.

Conversion of the high-mode solitons in strongly nonlocal nonlinear media

NASA Astrophysics Data System (ADS)

Zhang, Xiaping

2017-01-01

The conversion of high-mode solitons propagating in Strongly Nonlocal Nonlinear Media (SNNM) in three coordinate systems, namely, the elliptic coordinate system, the rectangular coordinate system and the cylindrical coordinate system, based on the Snyder-Mitchell Model that describes the paraxial beam propagating in SNNM, is discussed. Through constituting the trial solution with modulating the Gaussian beam by Ince polynomials, the closed-solution of Gaussian beams in elliptic coordinate is accessed. The Ince-Gaussian (IG) beams constitute the exact and continuous transition modes between Hermite-Gaussian beams and Laguerre-Gaussian (LG) beams, which is controlled by the elliptic parameter. The conditions of conversion in the three types of solitons are given in relation to the Gouy phase invariability in stable propagation. The profiles of the IG breather at a different propagating distance are numerically obtained, and the conversions of a few IG solitons are illustrated. The difference between the IG soliton and the corresponding LG soliton is remarkable from the Poynting vector and phase plots at their profiles along the propagating axis.

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

PubMed Central

Schröder, Tim; Trusheim, Matthew E.; Walsh, Michael; Li, Luozhou; Zheng, Jiabao; Schukraft, Marco; Sipahigil, Alp; Evans, Ruffin E.; Sukachev, Denis D.; Nguyen, Christian T.; Pacheco, Jose L.; Camacho, Ryan M.; Bielejec, Edward S.; Lukin, Mikhail D.; Englund, Dirk

2017-01-01

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ∼32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ∼2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ∼51 GHz and close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ∼1.4 times the natural linewidth. This method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors. PMID:28548097

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

DOE PAGES

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael; ...

2017-05-26

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Scalable focused ion beam creation of nearly lifetime-limited single quantum emitters in diamond nanostructures

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

Schroder, Tim; Trusheim, Matthew E.; Walsh, Michael

The controlled creation of defect centre—nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here we demonstrate direct, maskless creation of atom-like single silicon vacancy (SiV) centres in diamond nanostructures via focused ion beam implantation with ~32 nm lateral precision and <50 nm positioning accuracy relative to a nanocavity. We determine the Si+ ion to SiV centre conversion yield to be ~2.5% and observe a 10-fold conversion yield increase by additional electron irradiation. Low-temperature spectroscopy reveals inhomogeneously broadened ensemble emission linewidths of ~51 GHz andmore » close to lifetime-limited single-emitter transition linewidths down to 126±13 MHz corresponding to ~1.4 times the natural linewidth. Furthermore, this method for the targeted generation of nearly transform-limited quantum emitters should facilitate the development of scalable solid-state quantum information processors.« less

Status of a Power Processor for the Prometheus-1 Electric Propulsion System

NASA Technical Reports Server (NTRS)

Pinero, Luis R.; Hill, Gerald M.; Aulisio, Michael; Gerber, Scott; Griebeler, Elmer; Hewitt, Frank; Scina, Joseph

2006-01-01

NASA is developing technologies for nuclear electric propulsion for proposed deep space missions in support of the Exploration initiative under Project Prometheus. Electrical power produced by the combination of a fission-based power source and a Brayton power conversion and distribution system is used by a high specific impulse ion propulsion system to propel the spaceship. The ion propulsion system include the thruster, power processor and propellant feed system. A power processor technology development effort was initiated under Project Prometheus to develop high performance and lightweight power-processing technologies suitable for the application. This effort faces multiple challenges including developing radiation hardened power modules and converters with very high power capability and efficiency to minimize the impact on the power conversion and distribution system as well as the heat rejection system. This paper documents the design and test results of the first version of the beam supply, the design of a second version of the beam supply and the design and test results of the ancillary supplies.

Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges

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

Bouchard, Frédéric; De Leon, Israel; Schulz, Sebastian A.

Orbital angular momentum associated with the helical phase-front of optical beams provides an unbounded “space” for both classical and quantum communications. Among the different approaches to generate and manipulate orbital angular momentum states of light, coupling between spin and orbital angular momentum allows a faster manipulation of orbital angular momentum states because it depends on manipulating the polarisation state of light, which is simpler and generally faster than manipulating conventional orbital angular momentum generators. In this work, we design and fabricate an ultra-thin spin-to-orbital angular momentum converter, based on plasmonic nano-antennas and operating in the visible wavelength range that ismore » capable of converting spin to an arbitrary value of orbital angular momentum ℓ. The nano-antennas are arranged in an array with a well-defined geometry in the transverse plane of the beam, possessing a specific integer or half-integer topological charge q. When a circularly polarised light beam traverses this metasurface, the output beam polarisation switches handedness and the orbital angular momentum changes in value by ℓ=±2qℏ per photon. We experimentally demonstrate ℓ values ranging from ±1 to ±25 with conversion efficiencies of 8.6% ± 0.4%. Our ultra-thin devices are integratable and thus suitable for applications in quantum communications, quantum computations, and nano-scale sensing.« less

High-pulse energy Q-switched Tm3+:YAG laser for nonlinear frequency conversion to the mid-IR

NASA Astrophysics Data System (ADS)

Stöppler, Georg; Kieleck, Christelle; Eichhorn, Marc

2010-10-01

For some medical fields in laser surgery and as a pump source for nonlinear materials to generate mid-IR radiation, e.g. for countermeasure applications, it is very useful to have a solid-state laser with high pulse energy at 2 μm. The rare earth ion Thulium offers a cross relaxation and can thus be directly diode pumped with common laser diodes around 800 nm for an efficient pumping. However, it was not considered for high pulse energy operation due to the high saturation fluence of around 62 J/cm2 at 2 μm. A limiting factor has always been the damage threshold of the optical elements inside the cavity. One of the reasons is the strong thermal lens of YAG, which affects a change of the beam radius inside the resonator and additionally degrades the beam quality with increasing pump power. Using a new pump geometry of the Tm3+:YAG laser system, it is now possible to reach pulse energies > 13 mJ at a diffraction limited beam quality of M2 < 1.1. The Q-switched Tm3+:YAG laser system uses an AOM operating at 100 Hz and will be described in detail. Due to the high pulse energy and very good beam quality, this laser is very interesting for nonlinear parametric frequency conversion.

1.5% root-mean-square flat-intensity laser beam formed using a binary-amplitude spatial light modulator.

PubMed

Liang, Jinyang; Kohn, Rudolph N; Becker, Michael F; Heinzen, Daniel J

2009-04-01

We demonstrate a digital micromirror device (DMD)-based optical system that converts a spatially noisy quasi-Gaussian to an eighth-order super-Lorentzian flat-top beam. We use an error-diffusion algorithm to design the binary pattern for the Texas Instruments DLP device. Following the DMD, a telescope with a pinhole low-pass filters the beam and scales it to the desired sized image. Experimental measurements show a 1% root-mean-square (RMS) flatness over a diameter of 0.28 mm in the center of the flat-top beam and better than 1.5% RMS flatness over its entire 1.43 mm diameter. The power conversion efficiency is 37%. We develop an alignment technique to ensure that the DMD pattern is correctly positioned on the incident beam. An interferometric measurement of the DMD surface flatness shows that phase uniformity is maintained in the output beam. Our approach is highly flexible and is able to produce not only flat-top beams with different parameters, but also any slowly varying target beam shape. It can be used to generate the homogeneous optical lattice required for Bose-Einstein condensate cold atom experiments.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer

DOE PAGES

Reusswig, Philip D.; Nechayev, Sergey; Scherer, Jennifer M.; ...

2015-10-05

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd 3+ -doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CWmore » solar lasing threshold of 23 W-cm -2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.« less

A path to practical Solar Pumped Lasers via Radiative Energy Transfer

PubMed Central

Reusswig, Philip D.; Nechayev, Sergey; Scherer, Jennifer M.; Hwang, Gyu Weon; Bawendi, Moungi G.; Baldo, Marc. A.; Rotschild, Carmel

2015-01-01

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd3+-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm−2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns. PMID:26434400

A path to practical Solar Pumped Lasers via Radiative Energy Transfer.

PubMed

Reusswig, Philip D; Nechayev, Sergey; Scherer, Jennifer M; Hwang, Gyu Weon; Bawendi, Moungi G; Baldo, Marc A; Rotschild, Carmel

2015-10-05

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd(3+)-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm(-2), or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.

Third harmonic frequency generation by type-I critically phase-matched LiB3O5 crystal by means of optically active quartz crystal.

PubMed

Gapontsev, Valentin P; Tyrtyshnyy, Valentin A; Vershinin, Oleg I; Davydov, Boris L; Oulianov, Dmitri A

2013-02-11

We present a method of third harmonic generation at 355 nm by frequency mixing of fundamental and second harmonic radiation of an ytterbium nanosecond pulsed all-fiber laser in a type-I phase-matched LiB(3)O(5) (LBO) crystal where originally orthogonal polarization planes of the fundamental and second harmonic beams are aligned by an optically active quartz crystal. 8 W of ultraviolet light at 355 nm were achieved with 40% conversion efficiency from 1064 nm radiation. The conversion efficiency obtained in a type-I phase-matched LBO THG crystal was 1.6 times higher than the one achieved in a type-II LBO crystal at similar experimental conditions. In comparison to half-wave plates traditionally used for polarization alignment the optically active quartz crystal has much lower temperature dependence and requires simpler optical alignment.

Efficient Performance of Electrostatic Spray-Deposited TiO2 Blocking Layers in Dye-Sensitized Solar Cells after Swift Heavy Ion Beam Irradiation.

PubMed

Sudhagar, P; Asokan, K; Jung, June Hyuk; Lee, Yong-Gun; Park, Suil; Kang, Yong Soo

2011-12-01

A compact TiO2 layer (~1.1 μm) prepared by electrostatic spray deposition (ESD) and swift heavy ion beam (SHI) irradiation using oxygen ions onto a fluorinated tin oxide (FTO) conducting substrate showed enhancement of photovoltaic performance in dye-sensitized solar cells (DSSCs). The short circuit current density (Jsc = 12.2 mA cm(-2)) of DSSCs was found to increase significantly when an ESD technique was applied for fabrication of the TiO2 blocking layer, compared to a conventional spin-coated layer (Jsc = 8.9 mA cm(-2)). When SHI irradiation of oxygen ions of fluence 1 × 10(13) ions/cm(2) was carried out on the ESD TiO2, it was found that the energy conversion efficiency improved mainly due to the increase in open circuit voltage of DSSCs. This increased energy conversion efficiency seems to be associated with improved electronic energy transfer by increasing the densification of the blocking layer and improving the adhesion between the blocking layer and the FTO substrate. The adhesion results from instantaneous local melting of the TiO2 particles. An increase in the electron transport from the blocking layer may also retard the electron recombination process due to the oxidized species present in the electrolyte. These findings from novel treatments using ESD and SHI irradiation techniques may provide a new tool to improve the photovoltaic performance of DSSCs.

Efficient Performance of Electrostatic Spray-Deposited TiO2 Blocking Layers in Dye-Sensitized Solar Cells after Swift Heavy Ion Beam Irradiation

PubMed Central

2011-01-01

A compact TiO2 layer (~1.1 μm) prepared by electrostatic spray deposition (ESD) and swift heavy ion beam (SHI) irradiation using oxygen ions onto a fluorinated tin oxide (FTO) conducting substrate showed enhancement of photovoltaic performance in dye-sensitized solar cells (DSSCs). The short circuit current density (Jsc = 12.2 mA cm-2) of DSSCs was found to increase significantly when an ESD technique was applied for fabrication of the TiO2 blocking layer, compared to a conventional spin-coated layer (Jsc = 8.9 mA cm-2). When SHI irradiation of oxygen ions of fluence 1 × 1013 ions/cm2 was carried out on the ESD TiO2, it was found that the energy conversion efficiency improved mainly due to the increase in open circuit voltage of DSSCs. This increased energy conversion efficiency seems to be associated with improved electronic energy transfer by increasing the densification of the blocking layer and improving the adhesion between the blocking layer and the FTO substrate. The adhesion results from instantaneous local melting of the TiO2 particles. An increase in the electron transport from the blocking layer may also retard the electron recombination process due to the oxidized species present in the electrolyte. These findings from novel treatments using ESD and SHI irradiation techniques may provide a new tool to improve the photovoltaic performance of DSSCs. PMID:27502653

Invited article: Broadband highly-efficient dielectric metadevices for polarization control

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

Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. Furthermore, by employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-platesmore » that can operate across multiple telecom bands with ~99% polarization conversion efficiency.« less

Invited article: Broadband highly-efficient dielectric metadevices for polarization control

DOE PAGES

Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.; ...

2016-06-06

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. Furthermore, by employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-platesmore » that can operate across multiple telecom bands with ~99% polarization conversion efficiency.« less

Theoretical studies of solar pumped lasers

NASA Technical Reports Server (NTRS)

Harries, Wynford L.

1990-01-01

One concept for collecting solar energy is to use large solar collectors and then use lasers as energy converters whose output beams act as transmission lines to deliver the energy to a destination. The efficiency of the process would be improved if the conversion could be done directly using solar pumped lasers, and the possibility of making such lasers is studied. There are many applications for such lasers, and these are examined. By including the applications first, the requirements for the lasers will be more evident. They are especially applicable to the Space program, and include cases where no other methods of delivering power seem possible. Using the lasers for conveying information and surveillance is also discussed. Many difficulties confront the designer of an efficient system for power conversion. These involve the nature of the solar spectrum, the method of absorbing the energy, the transfer of power into laser beams, and finally, the far field patterns of the beams. The requirements of the lasers are discussed. Specific laser configurations are discussed. The thrust is into gas laser systems, because for space applications, the laser could be large, and also the medium would be uniform and not subject to thermal stresses. Dye and solid lasers are treated briefly. For gas lasers, a chart of the various possibilities is shown, and the various families of gas lasers divided according to the mechanisms of absorbing solar radiation and of lasing. Several specific models are analyzed and evaluated. Overall conclusions for the program are summarized, and the performances of the lasers related to the requirements of various applications.

Efficient, high power, Q-switched Nd:YLF slab laser end-pumped by diode stack

NASA Astrophysics Data System (ADS)

Zhang, Hengli; Li, Daijun; Shi, Peng; Diart, Rober; Shell, Alexander; Haas, Claus R.; Du, Keming

2005-06-01

A high power diode stack end-pumped electro-optically Q-switched Nd:YLF slab laser with a stable and off-axis negative-branch confocal unstable hybrid resonator was demonstrated. By using a cylindrical lens in the stable direction the thermal lens effect was compensated. Pulse energy of 25 mJ was obtained with a pulse width of 22.4 ns at repetition rates of 500 Hz and a conversion efficiency of 22%. The stability was better than 0.8% and the beam propagation M2 factor was about 1.2.

Efficient sintering of nanocrystalline titanium dioxide films for dye solar cells via raster scanning laser

NASA Astrophysics Data System (ADS)

Mincuzzi, Girolamo; Vesce, Luigi; Reale, Andrea; Di Carlo, Aldo; Brown, Thomas M.

2009-09-01

By identifying the right combination of laser parameters, in particular the integrated laser fluence Φ, we fabricated dye solar cells (DSCs) with UV laser-sintered TiO2 films exhibiting a power conversion efficiency η =5.2%, the highest reported for laser-sintered devices. η is dramatically affected by Φ and a clear trend is reported. Significantly, DSCs fabricated by raster scanning the laser beam to sinter the TiO2 films are made as efficient as those with oven-sintered ones. These results, confirmed on three batches of cells, demonstrate the remarkable potential (noncontact, local, low cost, rapid, selective, and scalable) of scanning laser processing applied to DSC technology.

Broadband non-polarizing terahertz beam splitters with variable split ratio

NASA Astrophysics Data System (ADS)

Wei, Minggui; Xu, Quan; Wang, Qiu; Zhang, Xueqian; Li, Yanfeng; Gu, Jianqiang; Tian, Zhen; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2017-08-01

Seeking effective terahertz functional devices has always aroused extensive attention. Of particular interest is the terahertz beam splitter. Here, we have proposed, designed, manufactured, and tested a broadband non-polarizing terahertz beam splitter with a variable split ratio based on an all-dielectric metasurface. The metasurface was created by patterning a dielectric surface of the N-step phase gradient and etching to a few hundred micrometers. The conversion efficiency as high as 81% under the normal incidence at 0.7 THz was achieved. Meanwhile, such a splitter works well over a broad frequency range. The split ratio of the proposed design can be continuously tuned by simply shifting the metasurface, and the angle of emergences can also be easily adjusted by choosing the step of phase gradients. The proposed design is non-polarizing, and its performance is kept under different polarizations.

Three dimensional particle-in-cell simulations of electron beams created via reflection of intense laser light from a water target

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

Ngirmang, Gregory K., E-mail: ngirmang.1@osu.edu; Orban, Chris; Feister, Scott

We present 3D Particle-in-Cell (PIC) modeling of an ultra-intense laser experiment by the Extreme Light group at the Air Force Research Laboratory using the Large Scale Plasma (LSP) PIC code. This is the first time PIC simulations have been performed in 3D for this experiment which involves an ultra-intense, short-pulse (30 fs) laser interacting with a water jet target at normal incidence. The laser-energy-to-ejected-electron-energy conversion efficiency observed in 2D(3v) simulations were comparable to the conversion efficiencies seen in the 3D simulations, but the angular distribution of ejected electrons in the 2D(3v) simulations displayed interesting differences with the 3D simulations' angular distribution;more » the observed differences between the 2D(3v) and 3D simulations were more noticeable for the simulations with higher intensity laser pulses. An analytic plane-wave model is discussed which provides some explanation for the angular distribution and energies of ejected electrons in the 2D(3v) simulations. We also performed a 3D simulation with circularly polarized light and found a significantly higher conversion efficiency and peak electron energy, which is promising for future experiments.« less

Efficient quasi-monoenergetic ion beams up to 18 MeV/nucleon via self-generated plasma fields in relativistic laser plasmas

NASA Astrophysics Data System (ADS)

Palaniyappan, Sasi; Huang, Chengkun; Gautier, Donald; Hamilton, Christopher; Santiago, Miguel; Kreuzer, Christian; Shah, Rahul; Fernandez, Juan; Los Alamos National Laboratory Team; Ludwig-Maximilian-University Team

2015-11-01

Table-top laser-plasma ion accelerators seldom achieve narrow energy spreads, and never without serious compromises in efficiency, particle yield, etc. Using massive computer simulations, we identify a self-organizing scheme that exploits persisting self-generated plasma electric (~ TV/m) and magnetic (~ 104 Tesla) fields to reduce the ion energy spread after the laser exits the plasma - separating the ion acceleration from the energy spread reduction. Consistent with the scheme, we experimentally demonstrate aluminum and carbon ion beams with narrow spectral peaks at energies up to 310 MeV (11.5 MeV/nucleon) and 220 MeV (18.3 MeV/nucleon), respectively, with high conversion efficiency (~ 5%, i.e., 4J out of 80J laser). This is achieved with 0.12 PW high-contrast Gaussian laser pulses irradiating planar foils with optimal thicknesses of up to 250 nm that scale with laser intensity. When increasing the focused laser intensity fourfold (by reducing the focusing optic f/number twofold), the spectral-peak energy increases twofold. These results pave the way for next generation compact accelerators suitable for applications. For example, 400 MeV (33.3 MeV/nucleon) carbon-ion beam with narrow energy spread required for ion fast ignition could be generated using PW-class lasers.

Modulated phase matching and high-order harmonic enhancement mediated by the carrier-envelope phase

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

Faccio, Daniele; CNISM and Department of Physics and Mathematics, Universita dell'Insubria, Via Valleggio 11, I-22100 Como; Serrat, Carles

2010-01-15

The process of high-order harmonic generation in gases is numerically investigated in the presence of a few-cycle pulsed-Bessel-beam pump, featuring a periodic modulation in the peak intensity due to large carrier-envelope-phase mismatch. A two-decade enhancement in the conversion efficiency is observed and interpreted as the consequence of a mechanism known as a nonlinearly induced modulation in the phase mismatch.

Solar energy collection system

NASA Technical Reports Server (NTRS)

Selcuk, M. K. (Inventor)

1977-01-01

An improved solar energy collection system, having enhanced energy collection and conversion capabilities, is delineated. The system is characterized by a plurality of receivers suspended above a heliostat field comprising a multiplicity of reflector surfaces, each being adapted to direct a concentrated beam of solar energy to illuminate a target surface for a given receiver. A magnitude of efficiency, suitable for effectively competing with systems employed in collecting and converting energy extracted from fossil fuels, is indicated.

How coupling affects closely packed rectenna arrays used for wireless power transmission

NASA Astrophysics Data System (ADS)

Walls, Deidra; Choi, Sang H.; Yoon, Hargsoon; Geddis, Demetris; Song, Kyo D.

2017-04-01

The development of power transmission by microwave beam power harvesting attracts manufactures for use of wireless power transmission. Optimizing maximum conversion efficiency is affected by many design parameters, and has been mainly focused previously. Combining several rectennas in one array potentially aides in the amount of microwave energy that can be harvested for energy conversion. Closely packed rectenna arrays is the result of the demand to minimize size and weight for flexibility. This paper specifically focuses on the coupling effects on power; mutual coupling, comparing sparameters and gain total while varying effective parameters. This paper investigates how coupling between each dipole positively and negatively affects the microwave energy, harvesting, and the design limitations.

High power high repetition rate diode side-pumped Q-switched Nd:YAG rod laser

NASA Astrophysics Data System (ADS)

Lebiush, E.; Lavi, R.; Tzuk, Y.; Jackel, S.; Lallouz, R.; Tsadka, S.

1998-01-01

A Q-switched diode side-pumped Nd:YAG rod laser is presented. The design is based on close coupled diodes which are mounted side by side to a laser rod cut at Brewster angle. No intra-cavity optics are needed to compensate for the induced thermal lensing of the rod. This laser produces 10 W average power with 30 ns pulse width and beam quality of 1.3 times diffraction limited at 10 kHz repetition rate. The light to light conversion efficiency is 12%. The same average power and beam quality is kept while operating the laser at repetition rates up to 50 kHz.

Metasurface holograms reaching 80% efficiency.

PubMed

Zheng, Guoxing; Mühlenbernd, Holger; Kenney, Mitchell; Li, Guixin; Zentgraf, Thomas; Zhang, Shuang

2015-04-01

Surfaces covered by ultrathin plasmonic structures--so-called metasurfaces--have recently been shown to be capable of completely controlling the phase of light, representing a new paradigm for the design of innovative optical elements such as ultrathin flat lenses, directional couplers for surface plasmon polaritons and wave plate vortex beam generation. Among the various types of metasurfaces, geometric metasurfaces, which consist of an array of plasmonic nanorods with spatially varying orientations, have shown superior phase control due to the geometric nature of their phase profile. Metasurfaces have recently been used to make computer-generated holograms, but the hologram efficiency remained too low at visible wavelengths for practical purposes. Here, we report the design and realization of a geometric metasurface hologram reaching diffraction efficiencies of 80% at 825 nm and a broad bandwidth between 630 nm and 1,050 nm. The 16-level-phase computer-generated hologram demonstrated here combines the advantages of a geometric metasurface for the superior control of the phase profile and of reflectarrays for achieving high polarization conversion efficiency. Specifically, the design of the hologram integrates a ground metal plane with a geometric metasurface that enhances the conversion efficiency between the two circular polarization states, leading to high diffraction efficiency without complicating the fabrication process. Because of these advantages, our strategy could be viable for various practical holographic applications.

Characteristics of a KA-band third-harmonic peniotron driven by a high-quality linear axis-encircling electron beam

NASA Astrophysics Data System (ADS)

Zhao, Xiaoyun; Tuo, Xianguo; Ge, Qing; Peng, Ying

2017-12-01

We employ a high-quality linear axis-encircling electron beam generated by a Cuccia coupler to drive a Ka-band third-harmonic peniotron and develop a self-consistent nonlinear calculation code to numerically analyze the characteristics of the designed peniotron. It is demonstrated that through a Cuccia coupler, a 6 kV, 0.5 A pencil beam and an input microwave power of 16 kW at 10 GHz can generate a 37 kV, 0.5 A linear axis-encircling beam, and it is characterized by a very low velocity spread. Moreover, the electron beam guiding center deviation can be adjusted easily. Driven by such a beam, a 30 GHz, Ka-band third-harmonic peniotron is predicted to achieve a conversion efficiency of 51.0% and a microwave output power of 9.44 kW; the results are in good agreement with the Magic3D simulation. Using this code, we studied the factors influencing the peniotron performance, and it can provide some guidelines for the design of a Ka-band third-harmonic peniotron driven by a linear electron beam and can promote the application of high-harmonic peniotrons in practice.

Evaluation of cumulative dose for cone‐beam computed tomography (CBCT) scans within phantoms made from different compositions using Monte Carlo simulations

PubMed Central

Martin, Colin J.; Sankaralingam, Marimuthu; Oomen, Kurian; Gentle, David J.

2015-01-01

Measurement of cumulative dose f(0,150) with a small ionization chamber within standard polymethyl methacrylate (PMMA) CT head and body phantoms, 150 mm in length, is a possible practical method for cone‐beam computed tomography (CBCT) dosimetry. This differs from evaluating cumulative dose under scatter equilibrium conditions within an infinitely long phantom f(0,∞), which is proposed by AAPM TG‐111 for CBCT dosimetry. The aim of this study was to investigate the feasibility of using f(0,150) to estimate values for f(0,∞) in long head and body phantoms made of PMMA, polyethylene (PE), and water, using beam qualities for tube potentials of 80−140 kV. The study also investigated the possibility of using 150 mm PE phantoms for assessment of f(0,∞) within long PE phantoms, the ICRU/AAPM phantom. The influence of scan parameters, composition, and length of the phantoms was investigated. The capability of f(0,150) to assess f(0,∞) has been defined as the efficiency and assessed in terms of the ratios ϵ(f(0,150)/f(0,∞)). The efficiencies were calculated using Monte Carlo simulations for an On‐Board Imager (OBI) system mounted on a TrueBeam linear accelerator. Head and body scanning protocols with beams of width 40−500 mm were used. Efficiencies ϵ(PMMA/PMMA) and ϵ(PE/PE) as a function of beam width exhibited three separate regions. For beam widths <150 mm, ϵ(PMMA/PMMA) and ϵ(PE/PE) values were greater than 90% for the head and body phantoms. The efficiency values then fell rapidly with increasing beam width before levelling off at 74% for ϵ(PMMA/PMMA) and 69% for ϵ(PE/PE) for a 500 mm beam width. The quantities ϵ(PMMA/PE) and ϵ(PMMA/Water) varied with beam width in a different manner. Values at the centers of the phantoms for narrow beams were lower and increased to a steady state for ∼100−150 mm wide beams, before declining with increasing the beam width, whereas values at the peripheries decreased steadily with beam width. Results for ϵ(PMMA/PMMA) were virtually independent of tube potential, but there was more variation for ϵ(PMMA/PE) and ϵ(PMMA/Water). f(0,150) underestimated f(0,∞) for beam widths used for CBCT scans, thus it is necessary to use long phantoms, or apply conversion factors (Cfs) to measurements with standard PMMA CT phantoms. The efficiency values have been used to derive (Cfs) to allow evaluation of f(0,∞) from measurements of f(0,150). The (Cfs) only showed a weak dependence on scan parameters and scanner type, and so may be suitable for general application. PACS number: 87.55.K‐, 87.57.Q‐, 87.57.uq. PMID:26699590

Longitudinal density modulation and energy conversion in intense beams.

PubMed

Harris, J R; Neumann, J G; Tian, K; O'Shea, P G

2007-08-01

Density modulation of charged particle beams may occur as a consequence of deliberate action, or may occur inadvertently because of imperfections in the particle source or acceleration method. In the case of intense beams, where space charge and external focusing govern the beam dynamics, density modulation may, under some circumstances, be converted to velocity modulation, with a corresponding conversion of potential energy to kinetic energy. Whether this will occur depends on the properties of the beam and the initial modulation. This paper describes the evolution of discrete and continuous density modulations on intense beams and discusses three recent experiments related to the dynamics of density-modulated electron beams.

SU‐C‐105‐05: Reference Dosimetry of High‐Energy Electron Beams with a Farmer‐Type Ionization Chamber

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

Muir, B; Rogers, D

2013-06-15

Purpose: To investigate gradient effects and provide Monte Carlo calculated beam quality conversion factors to characterize the Farmer‐type NE2571 ion chamber for high‐energy reference dosimetry of clinical electron beams. Methods: The EGSnrc code system is used to calculate the absorbed dose to water and to the gas in a fully modeled NE2571 chamber as a function of depth in a water phantom. Electron beams incident on the surface of the phantom are modeled using realistic BEAMnrc accelerator simulations and electron beam spectra. Beam quality conversion factors are determined using calculated doses to water and to air in the chamber inmore » high‐energy electron beams and in a cobalt‐60 reference field. Calculated water‐to‐air stopping power ratios are employed for investigation of the overall ion chamber perturbation factor. Results: An upstream shift of 0.3–0.4 multiplied by the chamber radius, r-cav, both minimizes the variation of the overall ion chamber perturbation factor with depth and reduces the difference between the beam quality specifier (R{sub 5} {sub 0}) calculated using ion chamber simulations and that obtained with simulations of dose‐to‐water in the phantom. Beam quality conversion factors are obtained at the reference depth and gradient effects are optimized using a shift of 0.2r-cav. The photon‐electron conversion factor, k-ecal, amounts to 0.906 when gradient effects are minimized using the shift established here and 0.903 if no shift of the data is used. Systematic uncertainties in beam quality conversion factors are investigated and amount to between 0.4 to 1.1% depending on assumptions used. Conclusion: The calculations obtained in this work characterize the use of an NE2571 ion chamber for reference dosimetry of high‐energy electron beams. These results will be useful as the AAPM continues to review their reference dosimetry protocols.« less

Hollow wall to stabilize and enhance ignition hohlraums

NASA Astrophysics Data System (ADS)

Vandenboomgaerde, M.; Grisollet, A.; Bonnefille, M.; Clérouin, J.; Arnault, P.; Desbiens, N.; Videau, L.

2018-01-01

In the context of the indirect-drive scheme of the inertial-confinement fusion, performance of the gas-filled hohlraums at the National Ignition Facility appears to be reduced. Experiments ascertain a limited efficacy of the laser beam propagation and x-ray conversion. One identified issue is the growth of the gold plasma plume (or bubble) which is generated near the ends of the hohlraum by the impact of the laser beams. This bubble impedes the laser propagation towards the equator of the hohlraum. Furthermore, for high foot or low foot laser pulses, the gold-gas interface of the bubble can be unstable. If this instability should grow to mixing, the x-ray conversion could be degraded. A novel hollow-walled hohlraum is designed, which drastically reduces the growth of the gold bubble and stabilizes the gold-gas interface. The hollow walls are built from the combination of a thin gold foil and a gold domed-wall. We theoretically explain how the bubble expansion can be delayed and the gold-gas interface stabilized. This advanced design lets the laser beams reach the waist of the hohlraum. As a result, the x-ray drive on the capsule is enhanced, and more spherical implosions are obtained. Furthermore, this design only requires intermediate gas fill density to be efficient.

Optical Frequency Optimization of a High Intensity Laser Power Beaming System Utilizing VMJ Photovoltaic Cells

NASA Technical Reports Server (NTRS)

Raible, Daniel E.; Dinca, Dragos; Nayfeh, Taysir H.

2012-01-01

An effective form of wireless power transmission (WPT) has been developed to enable extended mission durations, increased coverage and added capabilities for both space and terrestrial applications that may benefit from optically delivered electrical energy. The high intensity laser power beaming (HILPB) system enables long range optical 'refueling" of electric platforms such as micro unmanned aerial vehicles (MUAV), airships, robotic exploration missions and spacecraft platforms. To further advance the HILPB technology, the focus of this investigation is to determine the optimal laser wavelength to be used with the HILPB receiver, which utilizes vertical multi-junction (VMJ) photovoltaic cells. Frequency optimization of the laser system is necessary in order to maximize the conversion efficiency at continuous high intensities, and thus increase the delivered power density of the HILPB system. Initial spectral characterizations of the device performed at the NASA Glenn Research Center (GRC) indicate the approximate range of peak optical-to-electrical conversion efficiencies, but these data sets represent transient conditions under lower levels of illumination. Extending these results to high levels of steady state illumination, with attention given to the compatibility of available commercial off-the-shelf semiconductor laser sources and atmospheric transmission constraints is the primary focus of this paper. Experimental hardware results utilizing high power continuous wave (CW) semiconductor lasers at four different operational frequencies near the indicated band gap of the photovoltaic VMJ cells are presented and discussed. In addition, the highest receiver power density achieved to date is demonstrated using a single photovoltaic VMJ cell, which provided an exceptionally high electrical output of 13.6 W/sq cm at an optical-to-electrical conversion efficiency of 24 percent. These results are very promising and scalable, as a potential 1.0 sq m HILPB receiver of similar construction would be able to generate 136 kW of electrical power under similar conditions.

Development of a fast scintillator based beam phase measurement system for compact superconducting cyclotrons

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

Bhattacharjee, Tanushyam; Kanti Dey, Malay; Dhara, Partha

2013-05-15

In an isochronous cyclotron, measurements of central phase of the ion beam with respect to rf and the phase width provide a way to tune the cyclotron for maximum energy gain per turn and efficient extraction. We report here the development of a phase measurement system and the measurements carried out at the Variable Energy Cyclotron Centre's (VECC's) K= 500 superconducting cyclotron. The technique comprises detecting prompt {gamma}-rays resulting from the interaction of cyclotron ion beam with an aluminium target mounted on a radial probe in coincidence with cyclotron rf. An assembly comprising a fast scintillator and a liquid light-guidemore » inserted inside the cyclotron was used to detect the {gamma}-rays and to transfer the light signal outside the cyclotron where a matching photo-multiplier tube was used for light to electrical signal conversion. The typical beam intensity for this measurement was a few times 10{sup 11} pps.« less

Space-based laser-driven MHD generator: Feasibility study

NASA Technical Reports Server (NTRS)

Choi, S. H.

1986-01-01

The feasibility of a laser-driven MHD generator, as a candidate receiver for a space-based laser power transmission system, was investigated. On the basis of reasonable parameters obtained in the literature, a model of the laser-driven MHD generator was developed with the assumptions of a steady, turbulent, two-dimensional flow. These assumptions were based on the continuous and steady generation of plasmas by the exposure of the continuous wave laser beam thus inducing a steady back pressure that enables the medium to flow steadily. The model considered here took the turbulent nature of plasmas into account in the two-dimensional geometry of the generator. For these conditions with the plasma parameters defining the thermal conductivity, viscosity, electrical conductivity for the plasma flow, a generator efficiency of 53.3% was calculated. If turbulent effects and nonequilibrium ionization are taken into account, the efficiency is 43.2%. The study shows that the laser-driven MHD system has potential as a laser power receiver for space applications because of its high energy conversion efficiency, high energy density and relatively simple mechanism as compared to other energy conversion cycles.

Properties and Frequency Conversion of High-Brightness Diode-Laser Systems

NASA Astrophysics Data System (ADS)

Boller, Klaus-Jochen; Beier, Bernard; Wallenstein, Richard

An overview of recent developments in the field of high-power, high-brightness diode-lasers, and the optically nonlinear conversion of their output into other wavelength ranges, is given. We describe the generation of continuous-wave (CW) laser beams at power levels of several hundreds of milliwatts to several watts with near-perfect spatial and spectral properties using Master-Oscillator Power-Amplifier (MOPA) systems. With single- or double-stage systems, using amplifiers of tapered or rectangular geometry, up to 2.85 W high-brightness radiation is generated at wavelengths around 810nm with AlGaAs diodes. Even higher powers, up to 5.2W of single-frequency and high spatial quality beams at 925nm, are obtained with InGaAs diodes. We describe the basic properties of the oscillators and amplifiers used. A strict proof-of-quality for the diode radiation is provided by direct and efficient nonlinear optical conversion of the diode MOPA output into other wavelength ranges. We review recent experiments with the highest power levels obtained so far by direct frequency doubling of diode radiation. In these experiments, 100mW single-frequency ultraviolet light at 403nm was generated, as well as 1W of single-frequency blue radiation at 465nm. Nonlinear conversion of diode radiation into widely tunable infrared radiation has recently yielded record values. We review the efficient generation of widely tunable single-frequency radiation in the infrared with diode-pumped Optical Parametric Oscillators (OPOs). With this system, single-frequency output radiation with powers of more than 0.5W was generated, widely tunable around wavelengths of 2.1,m and 1.65,m and with excellent spectral and spatial quality. These developments are clear indicators of recent advances in the field of high-brightness diode-MOPA systems, and may emphasize their future central importance for applications within a vast range of optical wavelengths.

PASOTRON high-energy microwave source

NASA Astrophysics Data System (ADS)

Goebel, Dan M.; Schumacher, Robert W.; Butler, Jennifer M.; Hyman, Jay, Jr.; Santoru, Joseph; Watkins, Ron M.; Harvey, Robin J.; Dolezal, Franklin A.; Eisenhart, Robert L.; Schneider, Authur J.

1992-04-01

A unique, high-energy microwave source, called PASOTRON (Plasma-Assisted Slow-wave Oscillator), has been developed. The PASOTRON utilizes a long-pulse E-gun and plasma- filled slow-wave structure (SWS) to produce high-energy pulses from a simple, lightweight device that utilizes no externally produced magnetic fields. Long pulses are obtained from a novel E-gun that employs a low-pressure glow discharge to provide a stable, high current- density electron source. The electron accelerator consists of a high-perveance, multi-aperture array. The E-beam is operated in the ion-focused regime where the plasma filling the SWS space-charge neutralizes the beam, and the self-pinch force compresses the beamlets and increases the beam current density. A scale-model PASOTRON, operating as a backward- wave oscillator in C-band with a 100-kV E-beam, has produced output powers in the 3 to 5 MW range and pulse lengths of over 100 microsecond(s) ec, corresponding to an integrated energy per pulse of up to 500 J. The E-beam to microwave-radiation power conversion efficiency is about 20%.

High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

NASA Astrophysics Data System (ADS)

Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

2018-04-01

High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

Electrode Coverage Optimization for Piezoelectric Energy Harvesting from Tip Excitation

PubMed Central

Chen, Guangzhu; Bai, Nan

2018-01-01

Piezoelectric energy harvesting using cantilever-type structures has been extensively investigated due to its potential application in providing power supplies for wireless sensor networks, but the low output power has been a bottleneck for its further commercialization. To improve the power conversion capability, a piezoelectric beam with different electrode coverage ratios is studied theoretically and experimentally in this paper. A distributed-parameter theoretical model is established for a bimorph piezoelectric beam with the consideration of the electrode coverage area. The impact of the electrode coverage on the capacitance, the output power and the optimal load resistance are analyzed, showing that the piezoelectric beam has the best performance with an electrode coverage of 66.1%. An experimental study was then carried out to validate the theoretical results using a piezoelectric beam fabricated with segmented electrodes. The experimental results fit well with the theoretical model. A 12% improvement on the Root-Mean-Square (RMS) output power was achieved with the optimized electrode converge ratio (66.1%). This work provides a simple approach to utilizing piezoelectric beams in a more efficient way. PMID:29518934

Laser-plasmas in the relativistic-transparency regime: Science and applications

NASA Astrophysics Data System (ADS)

Fernández, Juan C.; Cort Gautier, D.; Huang, Chengkung; Palaniyappan, Sasikumar; Albright, Brian J.; Bang, Woosuk; Dyer, Gilliss; Favalli, Andrea; Hunter, James F.; Mendez, Jacob; Roth, Markus; Swinhoe, Martyn; Bradley, Paul A.; Deppert, Oliver; Espy, Michelle; Falk, Katerina; Guler, Nevzat; Hamilton, Christopher; Hegelich, Bjorn Manuel; Henzlova, Daniela; Ianakiev, Kiril D.; Iliev, Metodi; Johnson, Randall P.; Kleinschmidt, Annika; Losko, Adrian S.; McCary, Edward; Mocko, Michal; Nelson, Ronald O.; Roycroft, Rebecca; Santiago Cordoba, Miguel A.; Schanz, Victor A.; Schaumann, Gabriel; Schmidt, Derek W.; Sefkow, Adam; Shimada, Tsutomu; Taddeucci, Terry N.; Tebartz, Alexandra; Vogel, Sven C.; Vold, Erik; Wurden, Glen A.; Yin, Lin

2017-05-01

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at "table-top" scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (˜104 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (˜0.1 T V/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 μm laser pulses irradiating planar foils up to 250 nm thick at 2-8 × 1020 W/cm2. These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ˜2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. The plans and prospects for further improvements and applications are also discussed.

Laser-plasmas in the relativistic-transparency regime: science and applications

DOE PAGES

Fernandez, Juan Carlos; Gautier, Donald Cort; Huang, Chengkun; ...

2017-05-30

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at “table-top” scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (~10 4 T, according to particle-in-cell simulations of the experiments) at the rear-sidemore » of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (~0.1 TV/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 μm laser pulses irradiating planar foils up to 250 nm thick at 2–8 × 10 20 W/cm 2. These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ~2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. Finally, we discuss the plans and prospects for further improvements and applications.« less

Development of a two photon/laser induced fluorescence technique for the detection of atmospheric OH radicals

NASA Technical Reports Server (NTRS)

Bradshaw, John

1990-01-01

The development of a new mid-IR laser source was the primary goal. Backward propagating stimulated D2 Raman frequency down conversion of a commercially available 1.06 micron Nd:YAG laser was shown to generate an efficient source of 1.56 micron radiation with near diffraction limited beam quality. The efficient generation of a 2.9 micron laser source was also achieved using backward propagating CH4 Raman frequency down conversion of the 1.56 micron pump. Slightly higher efficiencies were obtained for frequency down conversion of the 1.06 micron Nd:YAG using the H2 Raman shift yielding a near diffraction limited source in the 200 mJ range at 1.9 micron. Similar conversion efficiencies are anticipated as a result of extending the wavelength coverage of recently available Ti:sapphire pulse laser to not only cover the 740 to 860 nm fundamental wavelength range but also the .95 to 1.15 and 1.06 to 1.33 micron range using D2 and H2, respectively. The anticipated sensitivity of a TP-LIF OH sensor using this mid-IR source would give signal limited detection of 1.4 x 10(exp 5) OH/cu cm under boundary layer conditions and 5.5 x 10(exp 4) OH/cu cm under free troposphere sampling conditions for a five minute signal integration period. This level of performance coupled with the techniques non-perturbing nature and freedom from both interferences and background would allow reliable tropospheric OH measurement to be obtained under virtually any ambient condition of current interest, including interstitial and sampling.

Image-rotating, 4-mirror, ring optical parametric oscillator

DOEpatents

Smith, Arlee V.; Armstrong, Darrell J.

2004-08-10

A device for optical parametric amplification utilizing four mirrors oriented in a nonplanar configuration where the optical plane formed by two of the mirrors is orthogonal to the optical plane formed by the other two mirrors and with the ratio of lengths of the laser beam paths approximately constant regardless of the scale of the device. With a cavity length of less than approximately 110 mm, a conversion efficiency of greater than 45% can be achieved.

Frequency conversion system

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

2001-01-01

Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

The first measurements of soft x-ray flux from ignition scale Hohlraums at the National Ignition Facility using DANTE (invited)

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

Kline, J. L.; Widmann, K.; Warrick, A.

2010-10-15

The first 96 and 192 beam vacuum Hohlraum target experiments have been fielded at the National Ignition Facility demonstrating radiation temperatures up to 340 eV and fluxes of 20 TW/sr as viewed by DANTE representing an {approx}20 times flux increase over NOVA/Omega scale Hohlraums. The vacuum Hohlraums were irradiated with 2 ns square laser pulses with energies between 150 and 635 kJ. They produced nearly Planckian spectra with about 30{+-}10% more flux than predicted by the preshot radiation hydrodynamic simulations. To validate these results, careful verification of all component calibrations, cable deconvolution, and software analysis routines has been conducted. Inmore » addition, a half Hohlraum experiment was conducted using a single 2 ns long axial quad with an irradiance of {approx}2x10{sup 15} W/cm{sup 2} for comparison with NIF Early Light experiments completed in 2004. We have also completed a conversion efficiency test using a 128-beam nearly uniformly illuminated gold sphere with intensities kept low (at 1x10{sup 14} W/cm{sup 2} over 5 ns) to avoid sensitivity to modeling uncertainties for nonlocal heat conduction and nonlinear absorption mechanisms, to compare with similar intensity, 3 ns OMEGA sphere results. The 2004 and 2009 NIF half-Hohlraums agreed to 10% in flux, but more importantly, the 2006 OMEGA Au Sphere, the 2009 NIF Au sphere, and the calculated Au conversion efficiency agree to {+-}5% in flux, which is estimated to be the absolute calibration accuracy of the DANTEs. Hence we conclude that the 30{+-}10% higher than expected radiation fluxes from the 96 and 192 beam vacuum Hohlraums are attributable to differences in physics of the larger Hohlraums.« less

Efficient photovoltaic heterojunctions of indium tin oxides on silicon

NASA Technical Reports Server (NTRS)

Dubow, J. B.; Sites, J. R.; Burk, D. E.

1976-01-01

Heterojunction diodes of indium tin oxide films sputtered on to p-silicon using ion-beam techniques display significant photovoltaic effects when exposed to sunlight. Galvanomagnetic and optical measurements confirm that the oxide films are highly degenerate transparent semiconductors. At a tin oxide concentration of 10%, an open-circuit voltage of 0.51 V was observed along with a short-circuit current of 32 mA/sq cm, a fill factor of 0.70, and a conversion efficiency of 12%. As the concentration was raised to 70%, the voltage remained steady, the current fell to 27 mA/sq cm, and the fill factor fell to 0.60

One joule output from a diode-array-pumped Nd:YAG laser with side-pumped rod geometry

NASA Technical Reports Server (NTRS)

Kasinski, Jeffrey J.; Hughes, Will; Dibiase, Don; Bournes, Patrick; Burnham, Ralph

1992-01-01

Output of 1.25 J per pulse (1.064 micron) with an absolute optical efficiency of 28 percent and corresponding electrical efficiency of 10 percent was demonstrated in a diode-array-pumped Nd:YAG laser using a side-pumped rod geometry in a master-oscillator/power-amplifier configuration. In Q-switched operation, an output of 0.75 J in a 17-ns pulse was obtained. The fundamental laser output was frequency doubled in KTP with 60 percent conversion efficiency to obtain 0.45 J in a 16-ns pulse at 532 nm. The output beam had high spatial quality with pointing stability better than 40 microrad and a shot-to-shot pulse energy fluctuation of less than +/-3 percent.

The effect of thermal de-phasing on the beam quality of a high-power single-pass second harmonic generation

NASA Astrophysics Data System (ADS)

Sadat Hashemi, Somayeh; Ghavami Sabouri, Saeed; Khorsandi, Alireza

2018-04-01

We present a theoretical model in order to study the effect of a thermally loaded crystal on the quality of a second-harmonic (SH) beam generated in a high-power pumping regime. The model is provided based on using a particular structure of oven considered for MgO:PPsLT nonlinear crystal to compensate for the thermal de-phasing effect that as the pumping power reaches up to 50 W degrades the conversion efficiency and beam quality of the interacting beams. Hereupon, the quality of fundamental beam is involved in the modeling to investigate the final effect on the beam quality of generated SH beam. Beam quality evaluation is subsequently simulated using Hermite-Gaussian modal decomposition approach for a range of fundamental beam qualities varied from 1 to 3 and for different levels of input powers. To provide a meaningful comparison numerical simulation is correlated with real data deduced from a high-power SH generation (SHG) experimental device. It is found that when using the open-top oven scheme and fixing the fundamental M 2-factor at nearly 1, for a range of input powers changing from 15 to 30 W, the M 2-factor of SHG beam is degraded from 9% to 24%, respectively, confirming very good consistency with the reported experimental results.

High efficiency fourth-harmonic generation from nanosecond fiber master oscillator power amplifier

NASA Astrophysics Data System (ADS)

Mu, Xiaodong; Steinvurzel, Paul; Rose, Todd S.; Lotshaw, William T.; Beck, Steven M.; Clemmons, James H.

2016-03-01

We demonstrate high power, deep ultraviolet (DUV) conversion to 266 nm through frequency quadrupling of a nanosecond pulse width 1064 nm fiber master oscillator power amplifier (MOPA). The MOPA system uses an Yb-doped double-clad polarization-maintaining large mode area tapered fiber as the final gain stage to generate 0.5-mJ, 10 W, 1.7- ns single mode pulses at a repetition rate of 20 kHz with measured spectral bandwidth of 10.6 GHz (40 pm), and beam qualities of Mx 2=1.07 and My 2=1.03, respectively. Using LBO and BBO crystals for the second-harmonic generation (SHG) and fourth-harmonic generation (FHG), we have achieved 375 μJ (7.5 W) and 92.5 μJ (1.85 W) at wavelengths of 532 nm and 266 nm, respectively. To the best of our knowledge these are the highest narrowband infrared, green and UV pulse energies obtained to date from a fully spliced fiber amplifier. We also demonstrate high efficiency SHG and FHG with walk-off compensated (WOC) crystal pairs and tightly focused pump beam. An SHG efficiency of 75%, FHG efficiency of 47%, and an overall efficiency of 35% from 1064 nm to 266 nm are obtained.

Efficient visible and UV generation by frequency conversion of a mode-filtered fiber amplifier

NASA Astrophysics Data System (ADS)

Kliner, Dahv A. V.; Di Teodoro, Fabio; Koplow, Jeffrey P.; Moore, Sean W.; Smith, Arlee V.

2003-07-01

We have generated the second, third, fourth, and fifth harmonics of the output of a Yb-doped fiber amplifier seeded by a passively Q-switched Nd:YAG microchip laser. The fiber amplifier employed multimode fiber (25 μm core diameter, V ~ 7.4) to provide high-peak-power pulses, but diffraction-limited beam quality was obtained by use of bend-loss-induced mode filtering. The amplifier output had a pulse duration of 0.97 ns and smooth, transform-limited temporal and spectral profiles (~500 MHz linewidth). We obtained high nonlinear conversion efficiencies using a simple optical arrangement and critically phase-matched crystals. Starting with 320 mW of average power at 1064 nm (86 ´J per pulse at a 3.7 kHz repetition rate), we generated 160 mW at 532 nm, 38 mW at 355 nm, 69 mW at 266 nm, and 18 mW at 213 nm. The experimental results are in excellent agreement with calculations. Significantly higher visible and UV powers will be possible by operating the fiber amplifier at higher repetition rates and pulse energies and by further optimizing the nonlinear conversion scheme.

Lamb wave propagation in monocrystalline silicon wafers.

PubMed

Fromme, Paul; Pizzolato, Marco; Robyr, Jean-Luc; Masserey, Bernard

2018-01-01

Monocrystalline silicon wafers are widely used in the photovoltaic industry for solar panels with high conversion efficiency. Guided ultrasonic waves offer the potential to efficiently detect micro-cracks in the thin wafers. Previous studies of ultrasonic wave propagation in silicon focused on effects of material anisotropy on bulk ultrasonic waves, but the dependence of the wave propagation characteristics on the material anisotropy is not well understood for Lamb waves. The phase slowness and beam skewing of the two fundamental Lamb wave modes A 0 and S 0 were investigated. Experimental measurements using contact wedge transducer excitation and laser measurement were conducted. Good agreement was found between the theoretically calculated angular dependency of the phase slowness and measurements for different propagation directions relative to the crystal orientation. Significant wave skew and beam widening was observed experimentally due to the anisotropy, especially for the S 0 mode. Explicit finite element simulations were conducted to visualize and quantify the guided wave beam skew. Good agreement was found for the A 0 mode, but a systematic discrepancy was observed for the S 0 mode. These effects need to be considered for the non-destructive testing of wafers using guided waves.

Single-mode annular chirally-coupled core fibers for fiber lasers

NASA Astrophysics Data System (ADS)

Zhang, Haitao; Hao, He; He, Linlu; Gong, Mali

2018-03-01

Chirally-coupled core (CCC) fiber can transmit single fundamental mode and effectively suppresses higher-order mode (HOM) propagation, thus improve the beam quality. However, the manufacture of CCC fiber is complicated due to its small side core. To decrease the manufacture difficulty in China, a novel fiber structure is presented, defined as annular chirally-coupled core (ACCC) fiber, replacing the small side core by a larger side annulus. In this paper, we designed the fiber parameters of this new structure, and demonstrated that the new structure has a similar property of single mode with traditional CCC fiber. Helical coordinate system was introduced into the finite element method (FEM) to analyze the mode field in the fiber, and the beam propagation method (BPM) was employed to analyze the influence of the fiber parameters on the mode loss. Based on the result above, the fiber structure was optimized for efficient single-mode transmission, in which the core diameter is 35 μm with beam quality M2 value of 1.04 and an optical to optical conversion efficiency of 84%. In this fiber, fundamental mode propagates in an acceptable loss, while the HOMs decay rapidly.

Influence of Illumination on the Electrical Properties of p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs Heterojunction Grown by Molecular Beam Epitaxy (MBE)

NASA Astrophysics Data System (ADS)

Jum'h, I.; Abd El-Sadek, M. S.; Al-Taani, H.; Yahia, I. S.; Karczewski, G.

2017-02-01

Heterostructure p-(ZnMgTe/ZnTe:N)/CdTe/n-(CdTe:I)/GaAs was evaporated using molecular beam epitaxy and investigated for photovoltaic energy conversion application. The electrical properties of the studied heterostructure were measured and characterized in order to understand the relevant electrical transport mechanisms. Electrical properties derived from the current-voltage ( I- V) characteristics of solar cells provide essential information necessary for the analysis of performance losses and device efficiency. I- V characteristics are investigated in dark conditions and under different light intensities. All the electrical and power parameters of the heterostructure were measured, calculated and explained.

Compact intra-cavity frequency doubled line beam green laser by a laser diode array pumped

NASA Astrophysics Data System (ADS)

Yan, Boxia; Qi, Yan; Wang, Yanwei

2016-10-01

Compact, high power, and low-cost green laser light sources are needed in projection-related applications such as digital cinema, rear-projection television, simulators, and command and control stations. We report a LD array directly pumped intracavity SHG Nd:YVO4/PPMgLN laser without lens or waveguide in this letter. A compact 3.12 W green laser was demonstrated by intra-cavity frequency doubled using a PPMgLN bulk crystal by a 19-emitter LD array pumped(single bar), the conversion efficiency from input LD array was 9.2%. A line-beam output suitable for laser projectors was generated, which has the potential to be scalable to small volumes and low costs for laser projection displays.

Laser or charged-particle-beam fusion reactor with direct electric generation by magnetic flux compression

DOEpatents

Lasche, G.P.

1983-09-29

The invention is a laser or particle-beam-driven fusion reactor system which takes maximum advantage of both the very short pulsed nature of the energy release of inertial confinement fusion (ICF) and the very small volumes within which the thermonuclear burn takes place. The pulsed nature of ICF permits dynamic direct energy conversion schemes such as magnetohydrodynamic (MHD) generation and magnetic flux compression; the small volumes permit very compact blanket geometries. By fully exploiting these characteristics of ICF, it is possible to design a fusion reactor with exceptionally high power density, high net electric efficiency, and low neutron-induced radioactivity. The invention includes a compact blanket design and method and apparatus for obtaining energy utilizing the compact blanket.

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

Palma, Giuseppina; Cozzarini, Luca; Capria, Ennio

A home-made system for incident photon-to-electron conversion efficiency (IPCE) characterization, based on a double-beam UV-Vis spectrophotometer, has been set up. In addition to its low cost (compared to the commercially available apparatuses), the double-beam configuration gives the advantage to measure, autonomously and with no need for supplementary equipment, the lamp power in real time, compensating possible variations of the spectral emission intensity and quality, thus reducing measurement times. To manage the optical and electronic components of the system, a custom software has been developed. Validations carried out on a common silicon-based photodiode and on a dye-sensitized solar cell confirm themore » possibility to adopt this system for determining the IPCE of solar cells, including dye-sensitized ones.« less

An X-band high-impedance relativistic klystron amplifier with an annular explosive cathode

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

Zhu, Danni; Zhang, Jun, E-mail: zhangjun@nudt.edu.cn; Zhong, Huihuang

2015-11-15

The feasibility of employing an annular beam instead of a solid one in the X-band high-impedance relativistic klystron amplifier (RKA) is investigated in theory and simulation. Small-signal theory analysis indicates that the optimum bunching distance, fundamental current modulation depth, beam-coupling coefficient, and beam-loaded quality factor of annular beams are all larger than the corresponding parameters of solid beams at the same beam voltage and current. An annular beam RKA and a solid beam RKA with almost the same geometric parameters are compared in particle-in-cell simulation. Output microwave power of 100 MW, gain of 50 dB, and power conversion efficiency of 42% aremore » obtained in an annular beam RKA. The annular beam needs a 15% lower uniform guiding magnetic field than the solid beam. Our investigations demonstrate that we are able to use a simple annular explosive cathode immersed in a lower uniform magnetic field instead of a solid thermionic cathode in a complicated partially shielding magnetic field for designing high-impedance RKA, which avoids high temperature requirement, complicated electron-optical system, large area convergence, high current density, and emission uniformity for the solid beam. An equivalent method for the annular beam and the solid beam on bunching features is proposed and agrees with the simulation. The annular beam has the primary advantages over the solid beam that it can employ the immersing uniform magnetic field avoiding the complicated shielding magnetic field system and needs a lower optimum guiding field due to the smaller space charge effect.« less

Plasma chemical conversion of sulphur hexafluoride initiated by a pulsed electron beam

NASA Astrophysics Data System (ADS)

Kholodnaya, Galina; Sazonov, Roman; Ponomarev, Denis; Guzeeva, Tatiana

2017-01-01

This paper presents the results of the experimental investigation of plasma chemical conversion of sulphur hexafluoride initiated by a pulsed electron beam (TEA-500 pulsed electron accelerator) with the following characteristics: 400-450 keV electron energy, 60 ns pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. Experiments were conducted on the effect of the pulsed electron beam on SF6 and on mixtures of SF6 with O2, Ar, or N2. For the mixture of SF6 and oxygen, the results indicated chemical reactions involving the formation of a number of products of which one is sulphur, confirming the Wray - Fluorescence Analysis. The plasma chemical conversion of SF6 initiated by the pulsed electron beam was not detected when SF6 was mixed with Ar or N2, suggesting a possible mechanism for the reaction of SF6 in the presence of O2.

A dual-mode operation overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic mode output

NASA Astrophysics Data System (ADS)

Bai, Zhen; Zhang, Jun; Zhong, Huihuang

2016-04-01

An overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic (TEM) mode output is designed and presented, by using a kind of coaxial slow wave structure (SWS) with large transversal dimension and small distance between inner and outer conductors. The generator works in dual-mode operation mechanism. The electron beam synchronously interacts with 7π/8 mode of quasi-TEM, at the meanwhile exchanges energy with 3π/8 mode of TM01. The existence of TM01 mode, which is traveling wave, not only increases the beam-wave interaction efficiency but also improves the extraction efficiency. The large transversal dimension of coaxial SWS makes its power capacity higher than that of other reported millimeter-wave devices and the small distance between inner and outer conductors allows only two azimuthally symmetric modes to coexist. The converter after the SWS guarantees the mode purity of output power. Particle-in-cell simulation shows that when the diode voltage is 400 kV and beam current is 3.8 kA, the generation of microwave at 32.26 GHz with an output power of 611 MW and a conversion efficiency of 40% is obtained. The power percentage carried by TEM mode reaches 99.7% in the output power.

A dual-mode operation overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic mode output

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

Bai, Zhen; Zhang, Jun, E-mail: zhangjun@nudt.edu.cn; Zhong, Huihuang

2016-04-15

An overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic (TEM) mode output is designed and presented, by using a kind of coaxial slow wave structure (SWS) with large transversal dimension and small distance between inner and outer conductors. The generator works in dual-mode operation mechanism. The electron beam synchronously interacts with 7π/8 mode of quasi-TEM, at the meanwhile exchanges energy with 3π/8 mode of TM{sub 01}. The existence of TM{sub 01} mode, which is traveling wave, not only increases the beam-wave interaction efficiency but also improves the extraction efficiency. The large transversal dimension ofmore » coaxial SWS makes its power capacity higher than that of other reported millimeter-wave devices and the small distance between inner and outer conductors allows only two azimuthally symmetric modes to coexist. The converter after the SWS guarantees the mode purity of output power. Particle-in-cell simulation shows that when the diode voltage is 400 kV and beam current is 3.8 kA, the generation of microwave at 32.26 GHz with an output power of 611 MW and a conversion efficiency of 40% is obtained. The power percentage carried by TEM mode reaches 99.7% in the output power.« less

Two-color beam improvement of the colloidal particle lens array assisted surface nanostructuring

NASA Astrophysics Data System (ADS)

Afanasiev, Andrei; Bredikhin, Vladimir; Pikulin, Alexander; Ilyakov, Igor; Shishkin, Boris; Akhmedzhanov, Rinat; Bityurin, Nikita

2015-05-01

We consider laser nanostructuring of the material surface by means of a colloidal particle lens array. Here, the monolayer of dielectric micro- or nanospheres placed on the surface acts as an array of near-field lenses that focus the laser radiation into the multitude of distinct spots, allowing the formation of many structures in a single stage. We show that conversion of a small part of the energy of the femtosecond beam into the second harmonic (SH) is an efficient way to increase the surface density of obtained nanostructures. By combining the fundamental frequency and the SH, one benefits both from the power of the former and from the focusing ability of the latter. This combination provides an efficient nanostructuring with sphere diameter close to the wavelength of the second harmonic. The possibility to create arrays of nanostructures with surface density above 5 × 10 8 cm - 2 with femtosecond Ti:sapphire laser operating at 800 nm was demonstrated by employing 0.45 μm spheres.

A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

NASA Astrophysics Data System (ADS)

Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

2013-05-01

A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.

Simulation of a gigawatt level Ku-band overmoded Cerenkov type oscillator operated at low guiding magnetic field

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

Zhang, Hua; Shu, Ting, E-mail: mrtingshu@qq.com; Ju, Jinchuan

2014-03-15

We present the simulation results of a Ku-band overmoded Cerenkov type high power microwave oscillator. A guiding magnetic field as low as 0.6 T has been operated in the device. Overmoded slow wave structures with gradually tapered vanes are used in order to increase power capacity and the efficiency of beam-wave interaction. The drift cavity is adopted to enhance the beam-wave interaction of the device. After numerical optimization, the designed generator with an output microwave power of 1.2 GW, a frequency of 13.8 GHz, and a power conversion efficiency as high as 38% can be achieved, when the diode voltage and currentmore » are, respectively, 540 kV and 5.8 kA. The power compositions of TM{sub 0n} modes of the output microwave have been analyzed, the results of which show that TM{sub 01} mode takes over almost 95% of the power proportion.« less

Tests of positive ion beams from a microwave ion source for AMS

NASA Astrophysics Data System (ADS)

Schneider, R. J.; von Reden, K. F.; Hayes, J. M.; Wills, J. S. C.; Kern, W. G. E.; Kim, S.-W.

2000-10-01

A test facility has been constructed to evaluate high-current positive ion beams from small gaseous samples for AMS applications. The major components include a compact permanent magnet microwave ion source built at the AECL Chalk River Laboratory and now on loan from the University of Toronto, and a double-focusing spectrometer magnet on loan from Argonne National Laboratory. Samples are introduced by means of a silica capillary injection system. Loop injection into a carrier gas provides a stable feed for the microwave driven plasma. The magnetic analysis system is utilized to isolate carbon ions derived from CO 2 samples from other products of the plasma discharge, including argon ions of the carrier gas. With a smaller discharge chamber, we hope to exceed a conversion efficiency of 14% for carbon ions produced per atom, which we reported at AMS-7. The next step will be to construct an efficient charge-exchange cell, to produce negative ions for injection into the WHOI recombinator injector.

Energy harvesting from low frequency applications using piezoelectric materials

DOE PAGES

Li, Huidong; Tian, Chuan; Deng, Z. Daniel

2014-11-06

This paper reviewed the state of research on piezoelectric energy harvesters. Various types of harvester configurations, piezoelectric materials, and techniques used to improve the mechanical-to-electrical energy conversion efficiency were discussed. Most of the piezoelectric energy harvesters studied today have focused on scavenging mechanical energy from vibration sources due to their abundance in both natural and industrial environments. Cantilever beams have been the most studied structure for piezoelectric energy harvester to date because of the high responsiveness to small vibrations.

Efficient solar-pumped Nd:YAG laser by a double-stage light-guide/V-groove cavity

NASA Astrophysics Data System (ADS)

Almeida, Joana; Liang, Dawei

2011-05-01

Since the first reported Nd:YAG solar laser, researchers have been exploiting parabolic mirrors and heliostats for enhancing laser output performance. We are now investigating the production of an efficient solar-pumped laser for the reduction of magnesium from magnesium oxide, which could be an alternative solution to fossil fuel. Therefore both high conversion efficiency and excellent beam quality are imperative. By using a single fused silica light guide of rectangular cross section, highly concentrated solar radiation at the focal spot of a stationary parabolic mirror is efficiently transferred to a water-flooded V-groove pump cavity. It allows for the double-pass absorption of pump light along a 4mm diameter, 30mm length, 1.1at% Nd:YAG rod. Optimum pumping parameters and solar laser output power are found through ZEMAXTM non-sequential ray-tracing and LASCADTM laser cavity analysis. 11.0 W of multimode laser output power with excellent beam profile is numerically calculated, corresponding to 6.1W/m2 collection efficiency. To validate the proposed pumping scheme, an experimental setup of the double-stage light-guide/V-groove cavity was built. 78% of highly concentrated solar radiation was efficiently transmitted by the fused silica light guide. The proposed pumping scheme can be an effective solution for enhancing solar laser performances when compared to other side-pump configurations.

Heating efficiency evaluation with mimicking plasma conditions of integrated fast-ignition experiment.

PubMed

Fujioka, Shinsuke; Johzaki, Tomoyuki; Arikawa, Yasunobu; Zhang, Zhe; Morace, Alessio; Ikenouchi, Takahito; Ozaki, Tetsuo; Nagai, Takahiro; Abe, Yuki; Kojima, Sadaoki; Sakata, Shohei; Inoue, Hiroaki; Utsugi, Masaru; Hattori, Shoji; Hosoda, Tatsuya; Lee, Seung Ho; Shigemori, Keisuke; Hironaka, Youichiro; Sunahara, Atsushi; Sakagami, Hitoshi; Mima, Kunioki; Fujimoto, Yasushi; Yamanoi, Kohei; Norimatsu, Takayoshi; Tokita, Shigeki; Nakata, Yoshiki; Kawanaka, Junji; Jitsuno, Takahisa; Miyanaga, Noriaki; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Nagatomo, Hideo; Azechi, Hiroshi

2015-06-01

A series of experiments were carried out to evaluate the energy-coupling efficiency from heating laser to a fuel core in the fast-ignition scheme of laser-driven inertial confinement fusion. Although the efficiency is determined by a wide variety of complex physics, from intense laser plasma interactions to the properties of high-energy density plasmas and the transport of relativistic electron beams (REB), here we simplify the physics by breaking down the efficiency into three measurable parameters: (i) energy conversion ratio from laser to REB, (ii) probability of collision between the REB and the fusion fuel core, and (iii) fraction of energy deposited in the fuel core from the REB. These three parameters were measured with the newly developed experimental platform designed for mimicking the plasma conditions of a realistic integrated fast-ignition experiment. The experimental results indicate that the high-energy tail of REB must be suppressed to heat the fuel core efficiently.

Electro-optic harmonic conversion to switch a laser beam out of a cavity

DOEpatents

Haas, Roger A.; Henesian, Mark A.

1987-01-01

The invention is a switch to permit a laser beam to escape a laser cavity through the use of an externally applied electric field across a harmonic conversion crystal. Amplification takes place in the laser cavity, and then the laser beam is switched out by the laser light being harmonically converted with dichroic or polarization sensitive elements present to alter the optical path of the harmonically converted laser light. Modulation of the laser beam can also be accomplished by varying the external electric field.

Generation of 46 W green-light by frequency doubling of 96 W picosecond unpolarized Yb-doped fiber amplifier

NASA Astrophysics Data System (ADS)

Qi, Yaoyao; Yu, Haijuan; Zhang, Jingyuan; Zhang, Ling; He, Chaojian; Lin, Xuechun

2018-05-01

We demonstrated a high efficiency and high average power picosecond green light source based on SHG (second harmonic generation) of an unpolarized ytterbium-doped fiber amplifier chain. Using single-pass frequency doubling in two temperature-tuned type-I phase-matching LBO crystals, we were able to generate 46 W, >70 ps pulses at 532 nm from a fundamental beam at 1064 nm, whose output is 96 W, 4.8 μJ, with a repetition frequency of 20 MHz and nearly diffraction limited. The optical conversion efficiency was ∼48% in a highly compact design. To the best of our knowledge, this is the first reported on ps green source through SHG of an unpolarized fiber laser with such a high output and high efficiency.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends.

PubMed

Wang, G; Peebles, W A; Doyle, E J; Crocker, N A; Wannberg, C; Lau, C; Hanson, G R; Doane, J L

2017-10-01

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ∼40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE 11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. It was observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ∼1.5%-3%. The polarization rotation due to the helical corrugations was in the range ∼1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ∼2.5 dB at 50 GHz and ∼6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. The primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends

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

Wang, Guiding; Peebles, W. A.; Doyle, E. J.

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ~40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. We observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ~1.5%-3%. The polarizationmore » rotation due to the helical corrugations was in the range ~1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ~2.5 dB at 50 GHz and ~6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. Finally, the primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.« less

Sci-Thur PM: YIS - 07: Monte Carlo simulations to obtain several parameters required for electron beam dosimetry.

PubMed

Muir, B; Rogers, D; McEwen, M

2012-07-01

When current dosimetry protocols were written, electron beam data were limited and had uncertainties that were unacceptable for reference dosimetry. Protocols for high-energy reference dosimetry are currently being updated leading to considerable interest in accurate electron beam data. To this end, Monte Carlo simulations using the EGSnrc user-code egs_chamber are performed to extract relevant data for reference beam dosimetry. Calculations of the absorbed dose to water and the absorbed dose to the gas in realistic ion chamber models are performed as a function of depth in water for cobalt-60 and high-energy electron beams between 4 and 22 MeV. These calculations are used to extract several of the parameters required for electron beam dosimetry - the beam quality specifier, R 50 , beam quality conversion factors, k Q and k R50 , the electron quality conversion factor, k' R50 , the photon-electron conversion factor, k ecal , and ion chamber perturbation factors, P Q . The method used has the advantage that many important parameters can be extracted as a function of depth instead of determination at only the reference depth as has typically been done. Results obtained here are in good agreement with measured and other calculated results. The photon-electron conversion factors obtained for a Farmer-type NE2571 and plane-parallel PTW Roos, IBA NACP-02 and Exradin A11 chambers are 0.903, 0.896, 0.894 and 0.906, respectively. These typically differ by less than 0.7% from the contentious TG-51 values but have much smaller systematic uncertainties. These results are valuable for reference dosimetry of high-energy electron beams. © 2012 American Association of Physicists in Medicine.

Average Power and Brightness Scaling of Diamond Raman Lasers

DTIC Science & Technology

2012-01-07

was also reported [16] for Brewster angled surfaces (63.7 degrees from [110]) at rates similar to the present study when taking into consideration the... Brewster   cut  crystals were investigated.      The  output  power,  conversion  efficiency  and  beam  properties  of  the  DRL  were  investigated as...efficiency are likely to be achieved without the use of thermal  lens  or birefringence compensation.          By using an upgraded 50 W pump laser we have

Power combination of two phase-locked high power microwave beams from a new coaxial microwave source based on dual beams

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

Li, Yangmei; Zhang, Xiaoping, E-mail: plinafly@163.com; Zhang, Jiande

2014-10-15

The new coaxial high power microwave source based on dual beams has demonstrated two phase-locked output microwave beams generated by its two sub-sources. In order to achieve a single higher output power, we present a three-port waveguide-based power combiner to combine the two microwave beams. Particle-in-cell simulation results show that when the diode voltage is 675 kV and the guiding magnetic field is 0.8 T, a combined microwave with an average power of about 4.0 GW and a frequency of 9.74 GHz is generated; the corresponding power conversion efficiency is 29%. The combination effect of the combiner is further validated in the diodemore » voltage range from 675 kV to 755 kV as well as in the pulse regime. The simulations indicate that the maximum surface axial electric field strength of the electrodynamic structure is 720 kV/cm, which is relatively low corresponding to an output power of 4.0 GW. The stable combined output suggests the probability of long-pulse operation for the combined source.« less

Waveguide Harmonic Generator for the SIM

NASA Technical Reports Server (NTRS)

Chang, Daniel; Poberezhskiy, Ilya; Mulder, Jerry

2008-01-01

A second-harmonic generator (SHG) serves as the source of the visible laser beam in an onboard calibration scheme for NASA's planned Space Interferometry Mission (SIM), which requires an infrared laser beam and a visible laser beam coherent with the infrared laser beam. The SHG includes quasi-phase-matched waveguides made of MgO-doped, periodically poled lithium niobate, pigtailed with polarization- maintaining optical fibers. Frequency doubling by use of such waveguides affords the required combination of coherence and sufficient conversion efficiency for the intended application. The spatial period of the poling is designed to obtain quasi-phase- matching at a nominal middle excitation wavelength of 1,319.28 nm. The SHG is designed to operate at a warm bias (ambient temperature between 20 and 25 C) that would be maintained in its cooler environment by use of electric heaters; the heater power would be adjusted to regulate the temperature precisely and thereby maintain the required precision of the spatial period. At the state of development at the time of this reporting, the SHG had been packaged and subjected to most of its planned space-qualification tests.

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

Nishiuchi, Mamiko; Pirozhkov, Alexander S.; Sakaki, Hironao

From the interaction between the high-contrast ({approx}more than 10{sup 10}) 130 TW Ti:sapphire laser pulse and Stainless Steel-2.5 um-thick tape target, proton beam with energies up to 23 MeV with the conversion efficiency of {approx}1% is obtained. After plasma mirror installation for contrast improvement, from the interaction between the 30 TW laser pulse and thin-foil target installed on the target holder with the hole whose shape is associated with the design of the well-known Wehnelt electrode of electron-gun, a 7 MeV intense proton beam is controlled dynamically and energy selected by the self-induced quasi-static electric field on the target holder.more » From the highly divergent beam having continuous spectrum, which are the typical features of the laser-driven proton beams from the interactions between the short-pulse laser and solid target, the spatial distribution of 7 MeV proton bunch is well manipulated to be focused to an small spots with an angular distribution of {approx}10 mrad. The number of protons included in the bunch is >10{sup 6}.« less

Orbit-induced localized spin angular momentum in strong focusing of optical vectorial vortex beams

NASA Astrophysics Data System (ADS)

Li, Manman; Cai, Yanan; Yan, Shaohui; Liang, Yansheng; Zhang, Peng; Yao, Baoli

2018-05-01

Light beams may carry optical spin or orbital angular momentum, or both. The spin and orbital parts manifest themselves by the ellipticity of the state of polarization and the vortex structure of phase of light beams, separately. Optical spin and orbit interaction, arising from the interaction between the polarization and the spatial structure of light beams, has attracted enormous interest recently. The optical spin-to-orbital angular momentum conversion under strong focusing is well known, while the converse process, orbital-to-spin conversion, has not been reported so far. In this paper, we predict in theory that the orbital angular momentum can induce a localized spin angular momentum in strong focusing of a spin-free azimuthal polarization vortex beam. This localized longitudinal spin of the focused field can drive the trapped particle to spin around its own axis. This investigation provides a new degree of freedom for spinning particles by using a vortex phase, which may have considerable potentials in optical spin and orbit interaction, light-beam shaping, or optical manipulation.

Scaling high-order harmonic generation from laser-solid interactions to ultrahigh intensity.

PubMed

Dollar, F; Cummings, P; Chvykov, V; Willingale, L; Vargas, M; Yanovsky, V; Zulick, C; Maksimchuk, A; Thomas, A G R; Krushelnick, K

2013-04-26

Coherent x-ray beams with a subfemtosecond (<10(-15)  s) pulse duration will enable measurements of fundamental atomic processes in a completely new regime. High-order harmonic generation (HOHG) using short pulse (<100  fs) infrared lasers focused to intensities surpassing 10(18)  W cm(-2) onto a solid density plasma is a promising means of generating such short pulses. Critical to the relativistic oscillating mirror mechanism is the steepness of the plasma density gradient at the reflection point, characterized by a scale length, which can strongly influence the harmonic generation mechanism. It is shown that for intensities in excess of 10(21)  W cm(-2) an optimum density ramp scale length exists that balances an increase in efficiency with a growth of parametric plasma wave instabilities. We show that for these higher intensities the optimal scale length is c/ω0, for which a variety of HOHG properties are optimized, including total conversion efficiency, HOHG divergence, and their power law scaling. Particle-in-cell simulations show striking evidence of the HOHG loss mechanism through parametric instabilities and relativistic self-phase modulation, which affect the produced spectra and conversion efficiency.

Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC71BM devices

PubMed Central

Zhang, Yiwei; Parnell, Andrew J.; Pontecchiani, Fabio; Cooper, Joshaniel F. K.; Thompson, Richard L.; Jones, Richard A. L.; King, Stephen M.; Lidzey, David G.; Bernardo, Gabriel

2017-01-01

We demonstrate that the inclusion of a small amount of the co-solvent 1,8-diiodooctane in the preparation of a bulk-heterojunction photovoltaic device increases its power conversion efficiency by 20%, through a mechanism of transient plasticisation. We follow the removal of 1,8-diiodooctane directly after spin-coating using ellipsometry and ion beam analysis, while using small angle neutron scattering to characterise the morphological nanostructure evolution of the film. In PffBT4T-2OD/PC71BM devices, the power conversion efficiency increases from 7.2% to above 8.7% as a result of the coarsening of the phase domains. This coarsening process is assisted by thermal annealing and the slow evaporation of 1,8-diiodooctane, which we suggest, acts as a plasticiser to promote molecular mobility. Our results show that 1,8-diiodooctane can be completely removed from the film by a thermal annealing process at temperatures ≤100 °C and that there is an interplay between the evaporation rate of 1,8-diiodooctane and the rate of domain coarsening in the plasticized film which helps elucidate the mechanism by which additives improve device efficiency. PMID:28287164

Highly Efficient Small Form Factor LED Retrofit Lamp

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

Steven Allen; Fred Palmer; Ming Li

2011-09-11

This report summarizes work to develop a high efficiency LED-based MR16 lamp downlight at OSRAM SYLVANIA under US Department of Energy contract DE-EE0000611. A new multichip LED package, electronic driver, and reflector optic were developed for these lamps. At steady-state, the lamp luminous flux was 409 lumens (lm), luminous efficacy of 87 lumens per watt (LPW), CRI (Ra) of 87, and R9 of 85 at a correlated color temperature (CCT) of 3285K. The LED alone achieved 120 lumens per watt efficacy and 600 lumen flux output at 25 C. The driver had 90% electrical conversion efficiency while maintaining excellent powermore » quality with power factor >0.90 at a power of only 5 watts. Compared to similar existing MR16 lamps using LED sources, these lamps had much higher efficacy and color quality. The objective of this work was to demonstrate a LED-based MR16 retrofit lamp for replacement of 35W halogen MR16 lamps having (1) luminous flux of 500 lumens, (2) luminous efficacy of 100 lumens per watt, (3) beam angle less than 40{sup o} and center beam candlepower of at least 1000 candelas, and (4) excellent color quality.« less

Feasibility of Traveling Wave Direct Energy Conversion of Fission Reaction Fragments

NASA Technical Reports Server (NTRS)

Tarditi, A. G.; George, J. A.; Miley, G. H.; Scott, J. H.

2013-01-01

Fission fragment direct energy conversion has been considered in the past for the purpose of increasing nuclear power plant efficiency and for advanced space propulsion. Since the fragments carry electric charge (typically in the order of 20 e) and have 100 MeV-range kinetic energy, techniques utilizing very high-voltage DC electrodes have been considered. This study is focused on a different approach: the kinetic energy of the charged fission fragments is converted into alternating current by means of a traveling wave coupling scheme (Traveling Wave Direct Energy Converter, TWDEC), thereby not requiring the utilization of high voltage technology. A preliminary feasibility analysis of the concept is introduced based on a conceptual level study and on a particle simulation model of the beam dynamics.

A study of electric transmission lines for use on the lunar surface

NASA Technical Reports Server (NTRS)

Gaustad, Krista L.; Gordon, Lloyd B.; Weber, Jennifer R.

1994-01-01

The sources for electrical power on a lunar base are said to include solar/chemical, nuclear (static conversion), and nuclear (dynamic conversion). The transmission of power via transmission lines is more practical than power beaming or superconducting because of its low cost and reliable, proven technology. Transmission lines must have minimum mass, maximum efficiency, and the ability to operate reliably in the lunar environment. The transmission line design includes conductor material, insulator material, conductor geometry, conductor configuration, line location, waveform, phase selection, and frequency. This presentation oulines the design. Liquid and gaseous dielectrics are undesirable for long term use in the lunar vacuum due to a high probability of loss. Thus, insulation for high voltage transmission line will most likely be solid dielectric or vacuum insulation.

A home-made system for IPCE measurement of standard and dye-sensitized solar cells.

PubMed

Palma, Giuseppina; Cozzarini, Luca; Capria, Ennio; Fraleoni-Morgera, Alessandro

2015-01-01

A home-made system for incident photon-to-electron conversion efficiency (IPCE) characterization, based on a double-beam UV-Vis spectrophotometer, has been set up. In addition to its low cost (compared to the commercially available apparatuses), the double-beam configuration gives the advantage to measure, autonomously and with no need for supplementary equipment, the lamp power in real time, compensating possible variations of the spectral emission intensity and quality, thus reducing measurement times. To manage the optical and electronic components of the system, a custom software has been developed. Validations carried out on a common silicon-based photodiode and on a dye-sensitized solar cell confirm the possibility to adopt this system for determining the IPCE of solar cells, including dye-sensitized ones.

Some Thoughts on the Role of non-LTE Physics in ICF

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

Colvin, J. D.

An effort to develop sub-critical-density high-Z metal-doped and pure metal foams as laser-driven x-ray sources is described. The main idea is that the laser beams preferentially heat the electrons, and if the plasma is sufficiently low density so that the heating rate is greater than the equilibration rate via electron-ion collisions, then the electron temperature in the plasma is much greater than the ion temperature as long as the laser is on. In such a situation the plasma is not in local thermal equilibrium (LTE), it heats supersonically and volumetrically, and the conversion efficiency of laser beam energy to multi-keVmore » L-shell and K-shell radiation is much higher than what it would be in LTE plasma.« less

Heralding efficiency and correlated-mode coupling of near-IR fiber-coupled photon pairs

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

Dixon, P. Ben; Rosenberg, Danna; Stelmakh, Veronika

We report on a systematic experimental study of heralding efficiency and generation rate of telecom-band infrared photon pairs generated by spontaneous parametric down-conversion and coupled to single mode optical fibers. We define the correlated-mode coupling efficiency--an inherent source efficiency--and explain its relation to heralding efficiency. For our experiment, we developed a reconfigurable computer controlled pump-beam and collection-mode optical apparatus which we used to measure the generation rate and correlated-mode coupling efficiency. The use of low-noise, high-efficiency superconducting-nanowire single-photon-detectors in this setup allowed us to explore focus configurations with low overall photon flux. The measured data agree well with theory andmore » we demonstrated a correlated-mode coupling efficiency of 97%±2%, which is the highest efficiency yet achieved for this type of system. These results confirm theoretical treatments and demonstrate that very high overall heralding efficiencies can, in principle, be achieved in quantum optical systems. We expect that these results and techniques will be widely incorporated into future systems that require, or benefit from, a high heralding efficiency.« less

Heralding efficiency and correlated-mode coupling of near-IR fiber-coupled photon pairs

DOE PAGES

Dixon, P. Ben; Rosenberg, Danna; Stelmakh, Veronika; ...

2014-10-06

We report on a systematic experimental study of heralding efficiency and generation rate of telecom-band infrared photon pairs generated by spontaneous parametric down-conversion and coupled to single mode optical fibers. We define the correlated-mode coupling efficiency--an inherent source efficiency--and explain its relation to heralding efficiency. For our experiment, we developed a reconfigurable computer controlled pump-beam and collection-mode optical apparatus which we used to measure the generation rate and correlated-mode coupling efficiency. The use of low-noise, high-efficiency superconducting-nanowire single-photon-detectors in this setup allowed us to explore focus configurations with low overall photon flux. The measured data agree well with theory andmore » we demonstrated a correlated-mode coupling efficiency of 97%±2%, which is the highest efficiency yet achieved for this type of system. These results confirm theoretical treatments and demonstrate that very high overall heralding efficiencies can, in principle, be achieved in quantum optical systems. We expect that these results and techniques will be widely incorporated into future systems that require, or benefit from, a high heralding efficiency.« less

Electron string ion sources for carbon ion cancer therapy accelerators

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

Boytsov, A. Yu.; Donets, D. E.; Donets, E. D.

2015-08-15

The type of the Electron String Ion Sources (ESIS) is considered to be the appropriate one to produce pulsed C{sup 4+} and C{sup 6+} ion beams for cancer therapy accelerators. In fact, the new test ESIS Krion-6T already now provides more than 10{sup 10} C{sup 4+} ions per pulse and about 5 × 10{sup 9} C{sup 6+} ions per pulse. Such ion sources could be suitable to apply at synchrotrons. It has also been found that Krion-6T can provide more than 10{sup 11} C{sup 6+} ions per second at the 100 Hz repetition rate, and the repetition rate can bemore » increased at the same or larger ion output per second. This makes ESIS applicable at cyclotrons as well. ESIS can be also a suitable type of ion source to produce the {sup 11}C radioactive ion beams. A specialized cryogenic cell was experimentally tested at the Krion-2M ESIS for pulse injection of gaseous species into the electron string. It has been shown in experiments with stable methane that the total conversion efficiency of methane molecules to C{sup 4+} ions reached 5%÷10%. For cancer therapy with simultaneous irradiation and precise dose control (positron emission tomography) by means of {sup 11}C, transporting to the tumor with the primary accelerated {sup 11}C{sup 4+} beam, this efficiency is preliminarily considered to be large enough to produce the {sup 11}C{sup 4+} beam from radioactive methane and to inject this beam into synchrotrons.« less

Laser-plasmas in the relativistic-transparency regime: Science and applications

PubMed Central

Cort Gautier, D.; Palaniyappan, Sasikumar; Albright, Brian J.; Favalli, Andrea; Hunter, James F.; Mendez, Jacob; Roth, Markus; Deppert, Oliver; Espy, Michelle; Guler, Nevzat; Hamilton, Christopher; Hegelich, Bjorn Manuel; Henzlova, Daniela; Ianakiev, Kiril D.; Iliev, Metodi; Johnson, Randall P.; Kleinschmidt, Annika; Losko, Adrian S.; McCary, Edward; Mocko, Michal; Nelson, Ronald O.; Roycroft, Rebecca; Schanz, Victor A.; Schaumann, Gabriel; Schmidt, Derek W.; Sefkow, Adam; Taddeucci, Terry N.; Yin, Lin

2017-01-01

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at “table-top” scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (∼104 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (∼0.1 T V/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 μm laser pulses irradiating planar foils up to 250 nm thick at 2–8 × 1020 W/cm2. These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ∼2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. The plans and prospects for further improvements and applications are also discussed. PMID:28652684

High helicity vortex conversion in a rubidium vapor

NASA Astrophysics Data System (ADS)

Chopinaud, Aurélien; Jacquey, Marion; Viaris de Lesegno, Bruno; Pruvost, Laurence

2018-06-01

The orbital angular momentum (OAM) of light is a quantity explored for communication and quantum technology, its key strength being a wide set of values offering a large basis for quantum working. In this context we have studied the vortex conversion from a red optical vortex to a blue one, for OAMs ranging -30 to +30 . The conversion is realized in a rubidium vapor, via the 5 S1 /2-5 D5 /285Rb two-photon transition done with a Gaussian beam at 780 nm plus a Laguerre-Gaussian beam at 776 nm with the OAM ℓ , producing a radiation at 420 nm . With copropagating input beams, we demonstrate a conversion from red to blue for high-ℓ input vortices. We show that the output blue vortex respects the azimuthal phase matching, has a size determined by the product of the input beams, and a power decreasing with ℓ , in agreement with their overlap. Its propagation indicates that the generated blue wave is a nearly pure Laguerre-Gaussian mode. The vortex converter thus permits a correct OAM transmission.

Compact high-efficiency 100-W-level diode-side-pumped Nd:YAG laser with linearly polarized TEM00 mode output.

PubMed

Xu, Yi-Ting; Xu, Jia-Lin; Guo, Ya-Ding; Yang, Feng-Tu; Chen, Yan-Zhong; Xu, Jian; Xie, Shi-Yong; Bo, Yong; Peng, Qin-Jun; Cui, Dafu; Xu, Zu-Yan

2010-08-20

We present a compact high-efficiency and high-average-power diode-side-pumped Nd:YAG rod laser oscillator operated with a linearly polarized fundamental mode. The oscillator resonator is based on an L-shaped convex-convex cavity with an improved module and a dual-rod configuration for birefringence compensation. Under a pump power of 344 W, a linearly polarized average output power of 101.4 W at 1064 nm is obtained, which corresponds to an optical-to-optical conversion efficiency of 29.4%. The laser is operated at a repetition rate of 400 Hz with a beam quality factor of M(2)=1.14. To the best of our knowledge, this is the highest optical-to-optical efficiency for a side-pumped TEM(00) Nd:YAG rod laser oscillator with a 100-W-level output ever reported.

SU-E-T-204: Comparison of Absorbed-Dose to Water in High-Energy Photon Beams Based On Addendum AAPM TG-51, IAEA TRS-398, and JSMP 12

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

Kinoshita, N; Kita, A; Yoshioka, C

Purpose: Several clinical reference dosimetry protocols for absorbed-dose to water have recently been published: The American Association of Physicists in Medicine (AAPM) published an Addendum to the AAPM’s TG-51 (Addendum TG-51) in April 2014, and the Japan Society of Medical Physics (JSMP) published the Japan Society of Medical Physics 12 (JSMP12), a clinical reference dosimetry protocol, in September 2012. This investigation compared and evaluated the absorbed-dose to water of high-energy photon beams according to Addendum TG-51, International Atomic Energy Agency Technical Report Series No. 398 (TRS-398), and JSMP12. Methods: Differences in the respective beam quality conversion factors with Addendum TG-51,more » TRS-398, and JSMP12 were analyzed and the absorbed-dose to water using 6- and 10-MV photon beams was measured according to the protocols recommended in Addendum TG-51, TRS-398, and JSMP12. The measurements were conducted using two Farmer-type ionization chambers, Exradin A12 and PTW 30013. Results: The beam quality conversion factors for both the 6- and 10-MV photon beams with Addendum TG-51 were within 0.6%, in agreement with the beam quality conversion factors with TRS-398 and JSMP12. The Exradin A12 provided an absorbed-dose to water ratio from 1.003 to 1.006 with TRS-398 / Addendum TG-51 and from 1.004 to 1.005 with JSMP 12 / Addendum TG-51, whereas the PTW 30013 provided a ratio of 1.001 with TRS-398 / Addendum TG-51 and a range from 0.997 to 0.999 with JSMP 12 / Addendum TG-51. Conclusion: Despite differences in the beam quality conversion factor, no major differences were seen in the absorbed-dose to water with Addendum TG-51, TRS-398, and JSMP12. However, Addendum TG-51 provides the most recent data for beam quality conversion factors based on Monte Carlo simulation and greater detail for the measurement protocol. Therefore, the absorbed-dose to water measured with Addendum TG-51 is an estimate with less uncertainty.« less

Guided ultrasonic wave beam skew in silicon wafers

NASA Astrophysics Data System (ADS)

Pizzolato, Marco; Masserey, Bernard; Robyr, Jean-Luc; Fromme, Paul

2018-04-01

In the photovoltaic industry, monocrystalline silicon wafers are employed for solar cells with high conversion efficiency. Micro-cracks induced by the cutting process in the thin wafers can lead to brittle wafer fracture. Guided ultrasonic waves would offer an efficient methodology for the in-process non-destructive testing of wafers to assess micro-crack density. The material anisotropy of the monocrystalline silicon leads to variations of the guided wave characteristics, depending on the propagation direction relative to the crystal orientation. Selective guided ultrasonic wave excitation was achieved using a contact piezoelectric transducer with custom-made wedges for the A0 and S0 Lamb wave modes and a transducer holder to achieve controlled contact pressure and orientation. The out-of-plane component of the guided wave propagation was measured using a non-contact laser interferometer. The phase slowness (velocity) of the two fundamental Lamb wave modes was measured experimentally for varying propagation directions relative to the crystal orientation and found to match theoretical predictions. Significant wave beam skew was observed experimentally, especially for the S0 mode, and investigated from 3D finite element simulations. Good agreement was found with the theoretical predictions based on nominal material properties of the silicon wafer. The important contribution of guided wave beam skewing effects for the non-destructive testing of silicon wafers was demonstrated.

Cross-polarized wave generation (XPW) for ultrafast laser pulse characterization and intensity contrast enhancement

NASA Astrophysics Data System (ADS)

Iliev, Marin

Good pulse quality, high peak power and tunable central wavelength are amongst the most desired qualities in modern lasers. The nonlinear effect cross-polarized wave generation (XPW), can be used in ultrafast laser systems to achieve various pulse quality enhancements. The XPW yield depends on the cube of the input intensity and acts as a spatio-temporal filter. It is orthogonally polarized to the input pulse and highly Gaussian. If the input pulse is well compressed, the output spectrum is smoother and broader. These features make XPW an ideal reference signal in pulse characterization techniques. This thesis presents a detailed analysis of the XPW conversion process, and describes novel applications to pulse characterization and high-quality pulse cleaning. An extensive computer model was developed to describe XPW generation via solution of the full coupled non-linear differential equations. The model accounts for dispersion inside the nonlinear crystal and uses split-step Fourier optics beam propagation to simulate the evolution of the electro-magnetic fields of the pump and XPW through free-space and imaging systems. A novel extension to the self-referenced spectral interferometry (SRSI) pulse characterization technique allows the retrieval of the energy and spectral content of the amplified spontaneous emission (ASE) present in ultrashort pulse amplifier systems. A novel double-pass XPW conversion scheme is presented. In it the beam passes through a single XPW crystal (BaF2) and is re-imaged with a curved mirror. The technique resulted in good (˜30%) efficiency without the spatial aberrations commonly seen in another arrangement that uses two crystals in succession. The modeling sheds light on the complicated nonlinear beam dynamics of the double-crystal conversion, including self- and cross-phase modulation, self-focusing, and the effects of, relative on-axis phase-difference, relative beam sizes, and wave-front curvature matching on seeded XPW conversion. Finally, a design is presented for exploiting the clean-up properties of XPW at the output of an optical parametric generation (OPA) setup in conjunction with an extremely compact prism compressor. The prisms material, separation and geometry are designed carefully to work at the correct wavelength of the OPA setup and are extrapolated to accommodate wavelengths, such as 2mum of parametric wave generation.

Characterization of the fast electrons distribution produced in a high intensity laser target interaction

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

Westover, B.; Lawrence Livermore National Laboratory, Livermore, California 94550; Chen, C. D.

2014-03-15

Experiments on the Titan laser (∼150 J, 0.7 ps, 2 × 10{sup 20} W cm{sup −2}) at the Lawrence Livermore National Laboratory were carried out in order to study the properties of fast electrons produced by high-intensity, short pulse laser interacting with matter under conditions relevant to Fast Ignition. Bremsstrahlung x-rays produced by these fast electrons were measured by a set of compact filter-stack based x-ray detectors placed at three angles with respect to the target. The measured bremsstrahlung signal allows a characterization of the fast electron beam spectrum, conversion efficiency of laser energy into fast electron kinetic energy and angular distribution. A Monte Carlo codemore » Integrated Tiger Series was used to model the bremsstrahlung signal and infer a laser to fast electron conversion efficiency of 30%, an electron slope temperature of about 2.2 MeV, and a mean divergence angle of 39°. Simulations were also performed with the hybrid transport code ZUMA which includes fields in the target. In this case, a conversion efficiency of laser energy to fast electron energy of 34% and a slope temperature between 1.5 MeV and 4 MeV depending on the angle between the target normal direction and the measuring spectrometer are found. The observed temperature of the bremsstrahlung spectrum, and therefore the inferred electron spectrum are found to be angle dependent.« less

Terahertz difference frequency generation in quantum cascade lasers on silicon

NASA Astrophysics Data System (ADS)

Jung, Seungyong; Kim, Jae Hyun; Jiang, Yifan; Vijayraghavan, Karun; Belkin, Mikhail A.

2017-02-01

We demonstrate that an application of a III-V-on-silicon hybrid concept to terahertz (THz) Cherenkov difference frequency generation (DFG) quantum cascade laser (QCL) sources (THz DFG-QCLs) can dramatically improve THz output power and mid-infrared-to-THz conversion efficiency. Completely processed THz DFG-QCLs grown on a 660-μm-thick native InP substrate are transfer-printed onto a 1-mm-thick high-resistive Si substrate using a 100-nm-thick SU-8 as an adhesive layer. Room temperature device performance of the reference InP and hybrid Si THz DFG-QCLs of the same ridge width (22 μm) and cavity length (4.2 mm) have been experimentally compared. The target THz frequency of 3.5 THz is selected for both devices using the dual-period first order surface gratings to select the mid-infrared pump wavelength of 994 cm-1 and 1110 cm-1. At the maximum bias current, the reference InP and hybrid Si devices produced THz power of 50 μW and 270 μW, respectively. The mid-infrared-to-THz conversion efficiency corresponds to 60 μW/W2 and 480 μW/W2, respectively, resulting in 5 times higher THz power and 8 times higher conversion efficiency from the best-performing hybrid devices. A hybrid Si device integrated in a Littrow external-cavity setup showed wavelength tuning from 1.3 THz to 4.3 THz with beam-steering free operation.

TLD and OSLD dosimetry systems for remote audits of radiotherapy external beam calibration.

PubMed

Alvarez, P; Kry, S F; Stingo, F; Followill, D

2017-11-01

The Imaging and Radiation Oncology Core QA Center in Houston (IROC-H) performs remote dosimetry audits of more than 20,000 megavoltage photon and electron beams each year. Both a thermoluminescent dosimeter (TLD-100) and optically stimulated luminescent dosimeter (OSLD; nanoDot) system are commissioned for this task, with the OSLD system being predominant due to the more time-efficient read-out process. The measurement apparatus includes 3 TLD or 2 OSLD in an acrylic mini-phantom, which are irradiated by the institution under reference geometry. Dosimetry systems are calibrated based on the signal-to-dose conversion established with reference dosimeters irradiated in a Co-60 beam, using a reference dose of 300 cGy for TLD and 100 cGy for OSLD. The uncertainty in the dose determination is 1.3% for TLD and 1.6% for OSLD at the one sigma level. This accuracy allows for a tolerance of ±5% to be used.

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

Rakhman, A.; Hafez, Mohamed A.; Nanda, Sirish K.

Here, a high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO 3 crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancementmore » of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.0 GeV and 50 μA.« less

Alignment system for SGII-Up laser facility

NASA Astrophysics Data System (ADS)

Gao, Yanqi; Cui, Yong; Li, Hong; Gong, Lei; Lin, Qiang; Liu, Daizhong; Zhu, Baoqiang; Ma, Weixin; Zhu, Jian; Lin, Zunqi

2018-03-01

The SGII-Up laser facility in Shanghai is one of the most important high-power laser facilities in China. It is designed to obtain 24 kJ (3ω) of energy with a square pulse of 3 ns using eight laser beams (two bundles). To satisfy the requirements for the safety, efficiency, and quality, an alignment system is developed for this facility. This alignment system can perform automatic alignment of the preamplifier system, main amplifier system, and harmonic conversion system within 30 min before every shot during the routine operation of the facility. In this article, an overview of the alignment system is first presented. Then, its alignment characteristics are discussed, along with the alignment process. Finally, experimental results, including the alignment results and the facility performance, are reported. The results show that the far-field beam pointing alignment accuracy is better than 3 μrad, and the alignment error of the near-field beam centering is no larger than 1 mm. These satisfy the design requirements very well.

Electron beam combined with hydrothermal treatment for enhancing the enzymatic convertibility of sugarcane bagasse

NASA Astrophysics Data System (ADS)

Duarte, C. L.; Ribeiro, M. A.; Oikawa, H.; Mori, M. N.; Napolitano, C. M.; Galvão, C. A.

2012-08-01

The use of microbial cellulolytic enzymes is the most efficient process to liberate glucose from cellulose in biomass without the formation of fermentation inhibitors. A combination of pretreatment technologies is an alternative way to increase the access of enzymes to cellulose, and consequently, the conversion yield. In this way, the present study reports on the enzymatic hydrolysis of SCB submitted to three kinds of pretreatment: electron beam processing (EBP), and EBP followed by hydrothermal (TH) and diluted acid (AH) treatment. SCB samples were irradiated using a radiation dynamics electron beam accelerator, and then submitted to thermal and acid (0.1% sulfuric acid) hydrolysis for 40 and 60 min at 180 °C. These samples were submitted to enzymatic hydrolysis (EH) using commercial preparations, including Celluclast 1.5 L and beta-glycosidase. The addition of diluted acid improved TH treatment allowing for a shorter application time. EBP with 50 kGy increased the enzymatic hydrolysis yield of cellulose by 20% after TH and 30% after AH.

Review of laser-driven ion sources and their applications.

PubMed

Daido, Hiroyuki; Nishiuchi, Mamiko; Pirozhkov, Alexander S

2012-05-01

For many years, laser-driven ion acceleration, mainly proton acceleration, has been proposed and a number of proof-of-principle experiments have been carried out with lasers whose pulse duration was in the nanosecond range. In the 1990s, ion acceleration in a relativistic plasma was demonstrated with ultra-short pulse lasers based on the chirped pulse amplification technique which can provide not only picosecond or femtosecond laser pulse duration, but simultaneously ultra-high peak power of terawatt to petawatt levels. Starting from the year 2000, several groups demonstrated low transverse emittance, tens of MeV proton beams with a conversion efficiency of up to several percent. The laser-accelerated particle beams have a duration of the order of a few picoseconds at the source, an ultra-high peak current and a broad energy spectrum, which make them suitable for many, including several unique, applications. This paper reviews, firstly, the historical background including the early laser-matter interaction studies on energetic ion acceleration relevant to inertial confinement fusion. Secondly, we describe several implemented and proposed mechanisms of proton and/or ion acceleration driven by ultra-short high-intensity lasers. We pay special attention to relatively simple models of several acceleration regimes. The models connect the laser, plasma and proton/ion beam parameters, predicting important features, such as energy spectral shape, optimum conditions and scalings under these conditions for maximum ion energy, conversion efficiency, etc. The models also suggest possible ways to manipulate the proton/ion beams by tailoring the target and irradiation conditions. Thirdly, we review experimental results on proton/ion acceleration, starting with the description of driving lasers. We list experimental results and show general trends of parameter dependences and compare them with the theoretical predictions and simulations. The fourth topic includes a review of scientific, industrial and medical applications of laser-driven proton or ion sources, some of which have already been established, while the others are yet to be demonstrated. In most applications, the laser-driven ion sources are complementary to the conventional accelerators, exhibiting significantly different properties. Finally, we summarize the paper.

LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

NASA Astrophysics Data System (ADS)

Ximendes, Erving Clayton; Rocha, Uéslen; Kumar, Kagola Upendra; Jacinto, Carlos; Jaque, Daniel

2016-06-01

We report on Ytterbium and Neodymium codoped LaF3 core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd3+ → Yb3+ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.

Flat-topped broadband rugate filters.

PubMed

Imenes, Anne G; McKenzie, David R

2006-10-20

A method of creating rugate interference filters that have flat-topped reflectance across an extended spectral region is presented. The method applies known relations from the classical coupled wave theory to develop a set of equations that gives the spatial frequency distribution of rugate cycles to achieve constant reflectance across a given spectral region. Two examples of the application of this method are discussed: a highly reflective coating for eye protection against harmful laser radiation incident from normal to 45 degrees , and a spectral beam splitter for efficient solar power conversion.

970-nm ridge waveguide diode laser bars for high power DWBC systems

NASA Astrophysics Data System (ADS)

Wilkens, Martin; Erbert, Götz; Wenzel, Hans; Knigge, Andrea; Crump, Paul; Maaßdorf, Andre; Fricke, Jörg; Ressel, Peter; Strohmaier, Stephan; Schmidt, Berthold; Tränkle, Günther

2018-02-01

de lasers are key components in material processing laser systems. While mostly used as pump sources for solid state or fiber lasers, direct diode laser systems using dense wavelength multiplexing have come on the market in recent years. These systems are realized with broad area lasers typically, resulting in beam quality inferior to disk or fiber lasers. We will present recent results of highly efficient ridge waveguide (RW) lasers, developed for dense-wavelength-beamcombining (DWBC) laser systems expecting beam qualities comparable to solid state laser systems and higher power conversion efficiencies (PCE). The newly developed RW lasers are based on vertical structures with an extreme double asymmetric large optical cavity. Besides a low vertical divergence these structures are suitable for RW-lasers with (10 μm) broad ridges, emitting in a single mode with a good beam quality. The large stripe width enables a lateral divergence below 10° (95 % power content) and a high PCE by a comparably low series resistance. We present results of single emitters and small test arrays under different external feedback conditions. Single emitters can be tuned from 950 nm to 975 nm and reach 1 W optical power with more than 55 % PCE and a beam quality of M2 < 2 over the full wavelength range. The spectral width is below 30 pm FWHM. 5 emitter arrays were stabilized using the same setup. Up to now we reached 3 W optical power, limited by power supply, with 5 narrow spectral lines.

Experimental characterization of a direct conversion amorphous selenium detector with thicker conversion layer for dual-energy contrast-enhanced breast imaging.

PubMed

Scaduto, David A; Tousignant, Olivier; Zhao, Wei

2017-08-01

Dual-energy contrast-enhanced imaging is being investigated as a tool to identify and localize angiogenesis in the breast, a possible indicator of malignant tumors. This imaging technique requires that x-ray images are acquired at energies above the k-shell binding energy of an appropriate radiocontrast agent. Iodinated contrast agents are commonly used for vascular imaging, and require x-ray energies greater than 33 keV. Conventional direct conversion amorphous selenium (a-Se) flat-panel imagers for digital mammography show suboptimal absorption efficiencies at these higher energies. We use spatial-frequency domain image quality metrics to evaluate the performance of a prototype direct conversion flat-panel imager with a thicker a-Se layer, specifically fabricated for dual-energy contrast-enhanced breast imaging. Imaging performance was evaluated in a prototype digital breast tomosynthesis (DBT) system. The spatial resolution, noise characteristics, detective quantum efficiency, and temporal performance of the detector were evaluated for dual-energy imaging for both conventional full-field digital mammography (FFDM) and DBT. The zero-frequency detective quantum efficiency of the prototype detector is improved by approximately 20% over the conventional detector for higher energy beams required for imaging with iodinated contrast agents. The effect of oblique entry of x-rays on spatial resolution does increase with increasing photoconductor thickness, specifically for the most oblique views of a DBT scan. Degradation of spatial resolution due to focal spot motion was also observed. Temporal performance was found to be comparable to conventional mammographic detectors. Increasing the a-Se thickness in direct conversion flat-panel imagers results in better performance for dual-energy contrast-enhanced breast imaging. The reduction in spatial resolution due to oblique entry of x-rays is appreciable in the most extreme clinically relevant cases, but may not profoundly affect reconstructed images due to the algorithms and filters employed. Degradation to projection domain spatial resolution is thus outweighed by the improvement in detective quantum efficiency for high-energy x-rays. © 2017 American Association of Physicists in Medicine.

Particle simulation of electromagnetic emissions from electrostatic instability driven by an electron ring beam on the density gradient

NASA Astrophysics Data System (ADS)

Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej

2018-04-01

This paper presents the wave mode conversion between electrostatic and electromagnetic waves on the plasma density gradient. We use 2-D electromagnetic code KEMPO2 implemented with the generation of density gradient to simulate such a conversion process. In the dense region, we use ring beam instability to generate electron Bernstein waves and we study the temporal evolution of wave spectra, velocity distributions, Poynting flux, and electric and magnetic energies to observe the wave mode conversion. Such a conversion process can be a source of electromagnetic emissions which are routinely measured by spacecraft on the plasmapause density gradient.

Current Status of Study on Hydrogen Production with Space Solar Power Systems (SSPS)

NASA Astrophysics Data System (ADS)

Mori, M.; Kagawa, H.; Nagayama, H.; Saito, Y.

2004-12-01

Japan Aerospace Exploration Agency (JAXA) has been conducting studies on Space Solar Power Systems (SSPS) using microwave and laser beams for years since FY1998 organizing a special committee and working groups. The microwave based SSPS are huge solar power systems that generate GW power by solar cells. The electric power is transmitted via microwave from the SSPS to the ground. In the laser based SSPS, a solar condenser equipped with lenses or mirrors and laser-generator would be put into orbit. A laser beam would be sent to Earth-based hydrogen generating device. We are proposing a roadmap that consists of a stepwise approach to achieve commercial SSPS in 20-30 years. The first step is 50kW class Technology Demonstration Satellite to demonstrate microwave power transmission. The second step is to demonstrate robotic assembly of 10MW class large scale flexible structure in space on ISS co-orbit. The third step is to build a prototype SSPS in GEO. The final step is to build commercial SSPS in GEO. We continue the study of SSPS concepts and architectures, technology flight demonstration and major technology development. System design of tens of kW class Technology Demonstration Satellite and conceptual study of 10MW class demonstration system on ISS co-orbit are also conducted. Several key technologies which are needed to be developed in appropriate R&D roadmap, such as high-voltage solar cell array, fiber type of direct solar pumping solid-state laser, high efficiency magnetron, thermal control technology and control technology of large scale flexible structure etc. are also investigated. In the study of concept design of commercial SSPS mentioned above, we have studied some configurations of both microwave based SSPS and laser based SSPS. In case of microwave based SSPS, the solar energy must be converted to electricity and then converted to a microwave beam. The on-ground rectifying antenna will collect the microwave beam and convert it to electricity to connect to commercial power grids. From the past experiences of the conceptual design of the1GW class SSPS, it is clear that system with the mirrors and modularized unit which integrated solar cells and microwave power transmitters is promising. In this type of SSPS, the solar lights are directed to the energy conversion unit integrated solar cells and microwave power transmitters using mirrors. The key factor in designing systems is feasibility of thermal system. Considering above these factors, some reference models are being considered now. FY2003 reference model is the model for formation flight without the center truss which connect to primary mirrors to energy conversion unit. Using this model as basis, we are carrying out examination from various viewpoints aiming at the cost minimum to build and maintain the systems. In case of laser based SSPS, the laser beam would be directly produced from the solar light using the direct solar pumping solid-state laser device. This laser beams would be collected on ground and used to produce hydrogen from seawater. The receiving / energy conversion station is settled on an ocean, and producing hydrogen can be stored and transported by ships to consumers. In designing laser based SSPS, conversion efficiency of the direct solar pumping solid-state laser and feasibility of thermal system are critical factors. Since magnification of solar concentrator is very high, improvement of thermal control system is important. Feasibility of its ground facilities and production technology of hydrogen using laser beams has been also studied. Both hydrogen generating systems with photo-catalyst device and electrolytic ones have been examined. From the past experiences of this study, high efficient electric power generating technology using the solar cell which suited the wavelength of laser is promising. The life cycle cost model of laser based SSPS was created and evaluated its validity. Sensitivity analysis of laser based SSPS are also continued aiming at hydrogen generating cost of around 20 cent per Nm3 . This paper presents a summary of studies on SSPS that JAXA has examined.

High-quality LaVO 3 films as solar energy conversion material

DOE PAGES

Zhang, Hai -Tian; Brahlek, Matthew; Ji, Xiaoyu; ...

2017-03-21

Mott insulating oxides and their heterostructures have recently been identified as potential photovoltaic materials with favorable absorption properties and an intrinsic built-in electric field that can efficiently separate excited electron hole pairs. At the same time, they are predicted to overcome the Shockley-Queisser limit due to strong electron electron interaction present. Despite these premises a high concentration of defects commonly observed in Mott insulating films acting as recombination centers can derogate the photovoltaic conversion efficiency. With use of the self-regulated growth kinetics in hybrid molecular beam epitaxy, this obstacle can be overcome. High-quality, stoichiometric LaVO 3 films were grown withmore » defect densities of in-gap states up to 2 orders of magnitude lower compared to the films in the literature, and a factor of 3 lower than LaVO 3 bulk single crystals. Photoconductivity measurements revealed a significant photoresponsivity increase as high as tenfold of stoichiometric LaVO 3 films compared to their nonstoichiometric counterparts. Furthermore, this work marks a critical step toward the realization of high-performance Mott insulator solar cells beyond conventional semiconductors.« less

A double-stream Xe:He jet plasma emission in the vicinity of 6.7 nm

NASA Astrophysics Data System (ADS)

Chkhalo, N. I.; Garakhin, S. A.; Golubev, S. V.; Lopatin, A. Ya.; Nechay, A. N.; Pestov, A. E.; Salashchenko, N. N.; Toropov, M. N.; Tsybin, N. N.; Vodopyanov, A. V.; Yulin, S.

2018-05-01

We present the results of investigations of extreme ultraviolet (EUV) light emission in the range from 5 to 10 nm. The light source was a pulsed "double-stream" Xe:He gas jet target irradiated by a laser beam with a power density of ˜1011 W/cm2. The radiation spectra were measured with a Czerny-Turner monochromator with a plane diffraction grating. The conversion efficiency of the laser energy into EUV radiation caused by Xe+14…+16 ion emission in the range of 6-8 nm was measured using a calibrated power meter. The conversion efficiency of the laser radiation into EUV in the vicinity of 6.7 nm was (2.17 ± 0.13)% in a 1 nm spectral band. In the spectral band of the real optical system (0.7% for La/B multilayer mirrors) emitted into the half-space, it was (0.1 ± 0.006)%. The results of this study provide an impetus for further research on laser plasma sources for maskless EUV lithography at a wavelength of 6.7 nm.

High-Quality LaVO3 Films as Solar Energy Conversion Material.

PubMed

Zhang, Hai-Tian; Brahlek, Matthew; Ji, Xiaoyu; Lei, Shiming; Lapano, Jason; Freeland, John W; Gopalan, Venkatraman; Engel-Herbert, Roman

2017-04-12

Mott insulating oxides and their heterostructures have recently been identified as potential photovoltaic materials with favorable absorption properties and an intrinsic built-in electric field that can efficiently separate excited electron-hole pairs. At the same time, they are predicted to overcome the Shockley-Queisser limit due to strong electron-electron interaction present. Despite these premises a high concentration of defects commonly observed in Mott insulating films acting as recombination centers can derogate the photovoltaic conversion efficiency. With use of the self-regulated growth kinetics in hybrid molecular beam epitaxy, this obstacle can be overcome. High-quality, stoichiometric LaVO 3 films were grown with defect densities of in-gap states up to 2 orders of magnitude lower compared to the films in the literature, and a factor of 3 lower than LaVO 3 bulk single crystals. Photoconductivity measurements revealed a significant photoresponsivity increase as high as tenfold of stoichiometric LaVO 3 films compared to their nonstoichiometric counterparts. This work marks a critical step toward the realization of high-performance Mott insulator solar cells beyond conventional semiconductors.

Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

NASA Astrophysics Data System (ADS)

Tawfieq, Mahmoud; Jensen, Ole Bjarlin; Hansen, Anders Kragh; Sumpf, Bernd; Paschke, Katrin; Andersen, Peter E.

2015-03-01

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7 W sum-frequency generated green laser at 509 nm is obtained, by frequency adding of 6.17 W from a 978 nm tapered diode laser with 8.06 W from a 1063 nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226 mW (CW) and 185 mW (mode-locked) at 1.7 W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54 nm (FWHM), indicating less than 20 fs pulse width.

Characterization of multilayer Thick-GEM geometries as 10B converters aiming thermal neutron detection

NASA Astrophysics Data System (ADS)

Natal da Luz, H.; Souza, F. A.; Moralles, M.; Carlin, N.; Oliveira, R. A. N.; Bregant, M.; Suaide, A. A. P.; Chubaci, J. F. D.; Matsuoka, M.; Silva, T. F.; Moro, M. V.; Rodrigues, C. L.; Munhoz, M. G.

2018-02-01

Boron-based thermal neutron detectors have recently regained some attention from the instrumentation community as a strong alternative to helium-3 detectors. From the existing concepts exploiting boron layers in position sensitive detectors, the Cascade [1] is the one that takes full advantage of the 2D capabilities of gaseous detectors, with the position resolution not limited by the architecture of the detector. In this work, a proposal for the Cascade detector, based on Thick-GEMs is presented, together with some preliminary studies of the suitable pitch that optimizes the neutron conversion efficiency, while keeping the collection efficiency intact. The characterization of Thick-GEM prototypes produced in Brazil with hole pitch from 0.75 to 3 mm shows that these devices already present a stable performance at low gains, also resulting in fair energy resolution, when cascaded with a standard KaptonTM 50 µm GEM. Results of the first attempts of boron film depositions with Ion Beam Assisted Deposition and characterization by Ion Beam Analysis are also presented.

Advanced laser architectures for high power eyesafe illuminators

NASA Astrophysics Data System (ADS)

Baranova, N.; Pati, B.; Stebbins, K.; Bystryak, I.; Rayno, M.; Ezzo, K.; DePriest, C.

2018-02-01

Q-Peak has demonstrated a novel pulsed eyesafe laser architecture operating with >50 mJ pulse energies at Pulse Repetition Frequencies (PRFs) as high as 320 Hz. The design leverages an Optical Parametric Oscillator (OPO) and Optical Parametric Amplifier (OPA) geometry, which provides the unique capability for high power in a comparatively compact package, while also offering the potential for additional eyesafe power scaling. The laser consists of a Commercial Off-the-Shelf (COTS) Q-switched front-end seed laser to produce pulse-widths around 10 ns at 1.06-μm, which is then followed by a pair of Multi-Pass Amplifier (MPA) architectures (comprised of side-pumped, multi-pass Nd:YAG slabs with a compact diode-pump-array imaging system), and finally involving two sequential nonlinear optical conversion architectures for transfer into the eyesafe regime. The initial seed beam is first amplified through the MPA, and then split into parallel optical paths. An OPO provides effective nonlinear conversion on one optical path, while a second MPA further amplifies the 1.06-μm beam for use in pumping an OPA on the second optical path. These paths are then recombined prior to seeding the OPA. Each nonlinear conversion subsystem utilizes Potassium Titanyl Arsenate (KTA) for effective nonlinear conversion with lower risk to optical damage. This laser architecture efficiently produces pulse energies of >50 mJ in the eyesafe band at PRFs as high as 320 Hz, and has been designed to fit within a volume of 4,500 in3 (0.074 m3 ). We will discuss theoretical and experimental details of the nonlinear optical system for achieving higher eyesafe powers.

Polymer-based solar cells having an active area of 1.6 cm{sup 2} fabricated via spray coating

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

Scarratt, N. W.; Griffin, J.; Zhang, Y.

We demonstrate the fabrication of polymer solar cells in which both a PEDOT:PSS hole transport and a PCDTBT:PC{sub 71}BM photoactive layer are deposited by spray-casting. Two device geometries are explored, with devices having a pixel area of 165 mm{sup 2} attaining a power conversion efficiency of 3.7%. Surface metrology indicates that the PEDOT:PSS and PCDTBT:PC{sub 71}BM layers have a roughness of 2.57 nm and 1.18 nm over an area of 100 μm{sup 2}. Light beam induced current mapping reveals fluctuations in current generation efficiency over length-scales of ∼2 mm, with the average photocurrent being 75% of its maximum value.

Electron Bernstein Wave Emission Studies on the TJ-II Stellarator

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

Caughman, John B; Fernandez, A.; Cappa, A.

2009-01-01

Electron Bernstein Wave (EBW) heating is important for high-beta plasma experiments and will be used for heating over-dense plasmas on TJ-II. TJ-II is a medium sized Heliac operating at CIEMAT in Madrid, whose plasmas are created and heated by ECH via two 300 kW gyrotrons at second harmonic X-mode (53.2 GHz), with additional heating provided by two neutral beam injectors. Theoretical work has shown that the most suitable scheme for launching EBWs in TJ-II is O-X-B mode conversion, which has acceptable heating efficiency for central densities above 1.2 x 1019 m-3.[1] A system based on a 28 GHz-100ms diode gyrotronmore » will be used to deliver 300 kW through a corrugated waveguide. The microwave heating beam will be directed and focused by a steering mirror located inside the vacuum vessel. Prior to the heating experiments, measurement of the thermal EBW emission (EBE) from the plasma is being made to help determine the optimum launch angle for EBW mode conversion, and also to provide an indication of the electron temperature evolution in over-dense plasmas. A dual-polarized quad-ridged broadband horn is used to measure the EBW emission and polarization at 28 GHz. Initial measurements indicate that the emission in under-dense plasmas corresponds to oblique electron cyclotron emission (ECE) and then converts to EBE when the plasma becomes over-dense during neutral beam injection.« less

High-power continuous-wave mid-infrared radiation generated by difference frequency mixing of diode-laser-seeded fiber amplifiers and its application to dual-beam spectroscopy

NASA Technical Reports Server (NTRS)

Lancaster, D. G.; Richter, D.; Curl, R. F.; Tittel, F. K.; Goldberg, L.; Koplow, J.

1999-01-01

We report the generation of up to 0.7 mW of narrow-linewidth (<60-MHz) radiation at 3.3 micrometers by difference frequency mixing of a Nd:YAG-seeded 1.6-W Yb fiber amplifier and a 1.5-micrometers diode-laser-seeded 0.6-W Er/Yb fiber amplifier in periodically poled LiNbO3. A conversion efficiency of 0.09%/W (0.47 mWW-2 cm-1) was achieved. A room-air CH4 spectrum acquired with a compact 80-m multipass cell and a dual-beam spectroscopic configuration indicates an absorption sensitivity of +/-2.8 x 10(-5) (+/-1 sigma), corresponding to a sub-parts-in-10(9) (ppb) CH4 sensitivity (0.8 ppb).

Control of energy sweep and transverse beam motion in induction linacs

NASA Astrophysics Data System (ADS)

Turner, W. C.

1991-05-01

Recent interest in the electron induction accelerator has focussed on its application as a driver for high power radiation sources; free electron laser (FEL), relativistic klystron (RK) and cyclotron autoresonance maser (CARM). In the microwave regime where many successful experiments have been carried out, typical beam parameters are: beam energy 1 to 10 MeV, current 1 to 3 kA and pulse width 50 nsec. Radiation source applications impose conditions on electron beam quality, as characterized by three parameters; energy sweep, transverse beam motion and brightness. These conditions must be maintained for the full pulse duration to assure high efficiency conversion of beam power to radiation. The microwave FEL that has been analyzed in the greatest detail requires energy sweep less than (+ or -) 1 pct., transverse beam motion less than (+ or -) 1 mm and brightness approx. 1 x 10(exp 8)A/sq m sq rad. In the visible region the requirements on these parameters become roughly an order of magnitude more strigent. With the ETAII accelerator at LLNL the requirements were achieved for energy sweep, transverse beam motion and brightness. The recent data and the advances that have made the improved beam quality possible are discussed. The most important advances are: understanding of focussing magnetic field errors and improvements in alignment of the magnetic axis, a redesign of the high voltage pulse distribution system between the magnetic compression modulators and the accelerator cells, and exploitation of a beam tuning algorithm for minimizing transverse beam motion. The prospects are briefly described for increasing the pulse repetition frequency to the range of 5 kHz and a delayed feedback method of regulating beam energy over very long pulse bursts, thus making average power megawatt level microwave sources at 140 GHz and above a possibility.

Laser power conversion system analysis, volume 2

NASA Technical Reports Server (NTRS)

Jones, W. S.; Morgan, L. L.; Forsyth, J. B.; Skratt, J. P.

1979-01-01

The orbit-to-ground laser power conversion system analysis investigated the feasibility and cost effectiveness of converting solar energy into laser energy in space, and transmitting the laser energy to earth for conversion to electrical energy. The analysis included space laser systems with electrical outputs on the ground ranging from 100 to 10,000 MW. The space laser power system was shown to be feasible and a viable alternate to the microwave solar power satellite. The narrow laser beam provides many options and alternatives not attainable with a microwave beam.

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

Pezzullo, Gianantonio

The Mu2e experiment will search for Charged Lepton Flavor Violation (CLFV) looking at the conversion of a muon into an electron in the field of an aluminum nucleus. Aboutmore » $$7\\cdot 10^{17}$$ muons, provided by a dedicated muon beam line in construction at the Fermi National Accelarator Laboratory (Fermilab), will be stopped in 3 years in the Aluminum target. The corresponding single event sensitivity will be $$2.5\\cdot 10^{-17}$$. The Standard Model of particle physics, even extendend to include the finite neutrino masses, predicts the ratio R μe between muon conversions and muon nuclear captures to be $$\\sim 10^{- 52}$$. Several extensions of the Standard Model predict R μe to be in the range of $$10^{-14} - 10^{-18}$$. % The current best experimental limit, set by the SINDRUM II experiment is $$7 \\cdot 10^{-13}$$ @ $$90\\%$$ CL. The Mu2e experiment plans to improve this experimental limit by four order of magnitude to test many of the possible extensions of the Standard Model. To reach this ambitious goal, the Mu2e experiment is expected to use an intense pulsed muon beam, and rely on a detector system composed of a straw tube tracker and a calorimeter made of pure CsI crystals. The calorimeter plays a central role in the Mu2e measurement, providing particle identification capabilities that are necessary for rejecting two of the most dangerous background sources that can mimic the μ⁻N → e⁻N conversion electron: cosmic muons and $$\\bar{p}$$ induced background. The calorimeter information allows also to improve the tracking performance. Thanks to a calorimeter-seeded track finder algorithm, it is possible to increase the track reconstruction efficiency, and make it more robust with respect to the occupancy level. Expected performances of the calorimeter have been studied in a beam test at the Beam Test Facility in Frascati (Rome, Italy). A reduced scale calorimeter prototype has been exposed to an electron beam, with energy varying from 80 to 140 MeV, for measuring the timing resolution and validate the Monte Carlo prediction. A timing resolution $$\\sigma_{\\rm t}<200$$ ps @ 100 MeV has been obtained. Combination of the background rejection performance, and the improvements in the track reconstruction, have then been used in the calculation of the expected Mu2e sensitivity.« less

Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types.

PubMed

Muir, B R; Rogers, D W O

2014-11-01

To provide a comprehensive investigation of electron beam reference dosimetry using Monte Carlo simulations of the response of 10 plane-parallel and 18 cylindrical ion chamber types. Specific emphasis is placed on the determination of the optimal shift of the chambers' effective point of measurement (EPOM) and beam quality conversion factors. The EGSnrc system is used for calculations of the absorbed dose to gas in ion chamber models and the absorbed dose to water as a function of depth in a water phantom on which cobalt-60 and several electron beam source models are incident. The optimal EPOM shifts of the ion chambers are determined by comparing calculations of R50 converted from I50 (calculated using ion chamber simulations in phantom) to R50 calculated using simulations of the absorbed dose to water vs depth in water. Beam quality conversion factors are determined as the calculated ratio of the absorbed dose to water to the absorbed dose to air in the ion chamber at the reference depth in a cobalt-60 beam to that in electron beams. For most plane-parallel chambers, the optimal EPOM shift is inside of the active cavity but different from the shift determined with water-equivalent scaling of the front window of the chamber. These optimal shifts for plane-parallel chambers also reduce the scatter of beam quality conversion factors, kQ, as a function of R50. The optimal shift of cylindrical chambers is found to be less than the 0.5 rcav recommended by current dosimetry protocols. In most cases, the values of the optimal shift are close to 0.3 rcav. Values of kecal are calculated and compared to those from the TG-51 protocol and differences are explained using accurate individual correction factors for a subset of ion chambers investigated. High-precision fits to beam quality conversion factors normalized to unity in a beam with R50 = 7.5 cm (kQ (')) are provided. These factors avoid the use of gradient correction factors as used in the TG-51 protocol although a chamber dependent optimal shift in the EPOM is required when using plane-parallel chambers while no shift is needed with cylindrical chambers. The sensitivity of these results to parameters used to model the ion chambers is discussed and the uncertainty related to the practical use of these results is evaluated. These results will prove useful as electron beam reference dosimetry protocols are being updated. The analysis of this work indicates that cylindrical ion chambers may be appropriate for use in low-energy electron beams but measurements are required to characterize their use in these beams.

Recent progress of the improved magnetically insulated transmission line oscillator.

PubMed

Fan, Yu-Wei; Zhong, Hui-Huang; Li, Zhi-Qiang; Shu, Ting; Zhang, Jian-De; Liu, Jin-Liang; Yang, Jian-Hua; Zhang, Jun; Yuan, Cheng-Wei; Luo, Ling

2008-03-01

The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube driven by a 550 kV, 57 kA, 50 ns electron beam. It has allowed us to generate 2.4 GW pulse of 22 ns duration. The recent progress of the improved MILO is presented in this paper. First, a field shaper cathode is introduced into the improved MILO to avoid the cathode flares in the triple point region. The experimental results show that the cathode flares are avoided, so the lifetime of the velvet cathode is longer than that of the taper cathode. Furthermore, the shot-to-shot reproducibility is better than that of the taper cathode. Second, In order to prolong the pulse duration and increase the radiated microwave power, a self-built 600 kV, 10 Omega, 80 ns pulser: SPARK-03 is employed to drive the improved MILO. Simulation and experimental investigation are performed. In simulation, when the improved MILO is driven by a 600 kV, 57 kA electron beam, high-power microwave is generated with output power of 4.15 GW, frequency of 1.76 GHz, and relevant power conversion efficiency of 12.0%. In experiments, when the diode voltage is 550 kV and current is 54 kA, the measured results are that the radiated microwave power is above 3.1 GW, the pulse duration is above 40 ns, the microwave frequency is about 1.755 GHz, and the power conversion efficiency is about 10.4%.

Optical domain analog to digital conversion methods and apparatus

DOEpatents

Vawter, Gregory A

2014-05-13

Methods and apparatus for optical analog to digital conversion are disclosed. An optical signal is converted by mapping the optical analog signal onto a wavelength modulated optical beam, passing the mapped beam through interferometers to generate analog bit representation signals, and converting the analog bit representation signals into an optical digital signal. A photodiode receives an optical analog signal, a wavelength modulated laser coupled to the photodiode maps the optical analog signal to a wavelength modulated optical beam, interferometers produce an analog bit representation signal from the mapped wavelength modulated optical beam, and sample and threshold circuits corresponding to the interferometers produce a digital bit signal from the analog bit representation signal.

Interaction of side-by-side fluidic harvesters in fractal grid-generated turbulence

NASA Astrophysics Data System (ADS)

Ferko, Kevin; Lachendro, David; Chiappazzi, Nick; Danesh-Yazdi, Amir H.

2018-03-01

While the vast majority of the literature in energy harvesting is dedicated to resonant harvesters, non-resonant harvesters, especially those that use turbulence-induced vibration to generate energy, have not been studied in as much detail. This is especially true for grid-generated turbulence. In this paper, the interaction of two side-by-side fluidic harvesters from a passive fractal grid-generated turbulent flow is considered. The fractal grid has been shown to significantly increase the turbulence generated in the flow which is the source of the vibration of the piezoelectric beams. In this experimental study, the influence of four parameters has been investigated: Beam lengths and configurations, mean flow velocity, distance from the grid and gap between the two beams. Experimental results show that the piezoelectric harvesters in fractal grid turbulence are capable of producing at least the same amount of power as those placed in passive rectangular grids with a larger pressure loss, allowing for a potentially significant increase in the efficiency of the energy conversion process, even though more experiments are required to study the behavior of the beams in homogeneous, fractal grid-generated turbulence.

Design of single-layer high-efficiency transmitting phase-gradient metasurface and high gain antenna

NASA Astrophysics Data System (ADS)

Zhang, Di; Yang, Xiaoqing; Su, Piqiang; Luo, Jiefang; Chen, Huijie; Yuan, Jianping; Li, Lixin

2017-12-01

In this paper, based on rotation phase-gradient principle, a single-layer, high-efficiency transmitting metasurface is designed and applied to high-gain antenna. In the case of circularly polarized incident wave, the PCR (polarization conversions ratio) of the metasurface element is greater than 90% in the band of 9.11-10.48 GHz. The transmitting wave emerges an anomalous refraction when left-handed circularly polarized wave are incident perpendicularly to the 1D phase-gradient metasurface, which is composed of cycle arrangement of 6 units with step value of 30°. The simulated anomalous refraction angle is 40.1°, coincided with the theoretical design value (40.6°). For further application, the 2D focused metasurface is designed to enhance the antenna performance while the left-handed circularly polarized antenna is placed at the focus. The simulated max gain is increased by 12 dB (182%) and the half-power beamwidth is reduced by 74.6°. The measured results are coincided with the simulations, which indicates the antenna has high directivity. The designed single-layer transmission metasurface has advantages of thin thickness (only 1.5 mm), high efficiency and light weight, and will have important application prospects in polarization conversion and beam control.

New PCBM/carbon based electron transport layer for perovskite solar cells.

PubMed

Mamun, Abdullah Al; Ava, Tanzila Tasnim; Zhang, Kai; Baumgart, Helmut; Namkoong, Gon

2017-07-21

Carbon is inherently abundant in nature and relatively inexpensive, which can potentially reduce the manufacturing cost of solar cells. In recent years, carbon has been used as a hole transport layer or counter electrode in perovskite solar cells. Herein, we demonstrate that carbon can also be used as a charge transport layer capable of enhancing the energy conversion efficiency of a CH 3 NH 3 PbI 3-x Cl x solar cell when carbon is combined with PCBM. Particularly, we have been able to deposit an ultra-flat carbon layer using an e-beam irradiation method, which exhibited much better conductivity than the competitive PCBM/C60 layer. In addition, quantitative analysis of interfacial charge dynamics shows that the quenching efficiency of PCBM/carbon is comparable to that of PCBM/C60 but better interface defect passivation and improved series and shunt resistances were observed when PCBM/carbon was employed. For the photovoltaic performance, the reference perovskite solar cell fabricated from the widely used PCBM/C60 has a power conversion efficiency (PCE) of 14% while the perovskite solar cell with PCBM/carbon has an increased PCE of 16%. Our results demonstrate the potential of the use of cost-effective carbon for perovskite solar cells, which could reduce production costs.

Ultrastable, high efficiency picosecond green light generation using K3B6O10Br series nonlinear optical crystals

NASA Astrophysics Data System (ADS)

Hou, Z. Y.; Xia, M. J.; Wang, L. R.; Xu, B.; Yan, D. X.; Meng, L. P.; Liu, L. J.; Xu, D. G.; Zhang, L.; Wang, X. Y.; Li, R. K.; Chen, C. T.

2017-09-01

Two perovskite-structure K3B6O10Br1-x Cl x (x  =  0 and 0.5) series nonlinear optical crystals were thoroughly investigated for their picosecond 532 nm laser pulses abilities and high power outputs were achieved via second harmonic generation (SHG) technique for the first time. SHG conversion efficiency of 57.3% with a 13.2 mm length K3B6O10Br (KBB) crystal was achieved using a laser source of pulse repetition rate of 10 Hz and pulse width of 25 ps, which is the highest conversion efficiency of ps visible laser based on KBB crystal. And by employing an 80 MHz, 10 ps fundamental laser beam, maximum power outputs of 12 W with K3B6O10Br0.5Cl0.5 (KBBC) and 11.86 W with KBB crystals were successfully demonstrated. Furthermore, the standard deviation jitters of the average power outputs are less than 0.6% and 1.17% by KBB and KBBC, respectively, showing ultrastable power stabilities favorable for practical applications. In addition, the other optical parameters including acceptance angle and temperature bandwidth were also investigated.

Technologies for Lunar Surface Power Systems Power Beaming and Transfer

NASA Astrophysics Data System (ADS)

Marzwell, Neville; Pogorzelski, Ronald J.; Chang, Kai; Little, Frank

2008-01-01

Wireless power transmission within a given working area is required or enabling for many NASA Exploration Systems. Fields of application include robotics, habitats, autonomous rendezvous and docking, life support, EVA, and many others. In robotics applications, for example, the robots must move in the working area without being hampered by power cables and, meanwhile, obtain a continuous and constant power from a power transmitter. The development of modern technology for transmitting electric power over free space has been studied for several decades, but its use in a system has been mainly limited to low power, 1-2 Vdc output voltage at a transmission distance of few meters for which relatively less than 0.5 mW/cm2 is required (e.g., Radio frequency identification RFID). Most of the rectenna conversion efficiency research to date has concentrated in low GHz frequency range of 2.45 to 10 GHz, with some work at 35 GHz. However, for space application, atmospheric adsorbtion is irrelevant and higher frequency systems with smaller transmit and receive apertures may be appropriate. For high power, most of the work on rectennas has concentrated on optimizing the conversion efficiency of the microwave rectifier element; the highest power demonstrated was 35 kW of power over a distance of 1.5 km. The objective of this paper is to establish the manner in which a very large number of very low power microwave devices can be synchronized to provide a beam of microwaves that can be used to efficiently and safely transport a significant amount of power to a remote location where it can be converted to dc (or ac) power by a ``rectenna.'' The proposed system is based on spatial power combining of the outputs of a large number of devices synchronized by mutual injection locking. We have demonstrated at JPL that such power could be achieved by combining 25 sources in a configuration that allows for convenient steering of the resulting beam of microwaves. Retrodirective beam steering for microwave power transmission (the ability to accurately track a moving receiver) has been demonstrated at Texas A&M. It is proposed that the next step in development of this concept is a modest scale up from 25 elements to 435 followed by a further scale up using such 435 element arrays as subarrays for a still larger retrodirective system. Ultimately, transmit antenna sizes on the order of 100 meters are envisioned permitting transfer levels on the order of 30 kW to aerial vehicles up to 20 km.

An Efficient Single Frequency Ho:YLF Laser for IPDA Lidar Applications

NASA Technical Reports Server (NTRS)

Yu, J.; Bai, Y.; Wong, T.; Reithmeier, K.; Petros, M.

2016-01-01

A highly efficient, versatile, single frequency 2-micron pulsed laser can be used in a pulsed Differential Absorption Lidar (DIAL) / Integrated Path Differential Absorption (IPDA) instrument to make precise, high-resolution measurements to investigate sources and sinks of CO2. For a direct detection IPDA lidar, the desired 2 ?m Ho:YLF laser should generate 30-40 mJ pulses at the repetition rate of 100 to 200 Hz, with short pulse length (<100 ns) and better than 2% wall plug efficiency. A Tm fiber laser in-band pumped Ho:YLF laser has been developed to meet this technical challenge. This Ho:YLF laser is designed in a four mirror ring resonator with bow tie configuration, which helps to obtain high beam quality. It is end-pumped by a 40 W linearly polarized Tm fiber laser at 1.94µm. The resonator length is 1.10 meters with output coupler reflectivity at 45%. The laser crystal size is 3 x 3 x 60 mm (w, h, l) with a doping concentration of 0.5% Holmium. The laser beam and pump beam are mode-matched in the active medium. Thus, the pump and laser beams have the same confocal parameters. Mode-matching is also helpful for operating the laser in a single transverse mode. The laser beam waist is slightly less than 0.5 mm at the center of the laser crystal. Based on quasi-four level modeling, pump absorption and saturation depend on laser intensity. Laser amplification and saturation also depend on the pump intensity in the crystal. The laser is injection seeded to obtain the single frequency required by an IPDA lidar measurement. The seed beam is entered into the resonator through an output coupler. The laser is mounted on a water cooled optical bench for stable and reliable operation. The size of the optical bench is 22.16 x 9.20 x 1.25 inches. It is stiffened so that the laser can be operated in any orientation of the optical bench. This packaged Ho:YLF laser is designed for either mobile trailer or airborne platform operation. The engineering prototype Ho:YLF laser has been fully characterized to demonstrate laser performance. Figure 1 shows the laser output power as a function of pump power at different pulse repetition rates from 100 Hz to 333 Hz. The threshold of the laser is less than 14 W. The slope efficiencies are 28%, 40%, 41% and 43% for pulse repetition rates of 100, 200, 250 and 333 Hz, respectively. Maximum power increases with the pulse repetition rate. Output power of 4.2 W, 6 W, 6.7 W, and 7.7 W is achieved for pulse repetition rates of 100, 200, 250 and 333Hz, respectively. This represents the optical conversion efficiency of 16.7%, 22.4%, 23.7%, and 26.5% at these various pulse repletion rates. It is the most efficient and compact Ho:YLF laser demonstrated in the high pulse energy (>20mJ) and moderate pulse repetition rate (100's Hz) operation range. As shown in Figure 1, the maximum pulse energy at 100 Hz is 42 mJ. This is limited due to optical damage. The laser stability is characterized and found to be very stable. A relative pulse energy standard deviation of 2% was measured. The beam quality of the Ho:YLF was measured by a Spiricon infrared laser beam camera. Figure 2 shows the beam profile image of the laser. Both the X-profile of the beam (horizontal direction) and the Y-profile of the beam (vertical direction) are well fitted by a Gaussian profile. The qualitative beam quality measurement shows excellent beam quality in both axis. The M-square value for the laser beam is measured at 1.06 and 1.09 for the x and y axis respectively.-

[Uncertainty of cross calibration-applied beam quality conversion factor for the Japan Society of Medical Physics 12].

PubMed

Kinoshita, Naoki; Kita, Akinobu; Takemura, Akihiro; Nishimoto, Yasuhiro; Adachi, Toshiki

2014-09-01

The uncertainty of the beam quality conversion factor (k(Q,Q0)) of standard dosimetry of absorbed dose to water in external beam radiotherapy 12 (JSMP12) is determined by combining the uncertainty of each beam quality conversion factor calculated for each type of ionization chamber. However, there is no guarantee that ionization chambers of the same type have the same structure and thickness, so there may be individual variations. We evaluated the uncertainty of k(Q,Q0) for JSMP12 using an ionization chamber dosimeter and linear accelerator without a specific device or technique in consideration of the individual variation of ionization chambers and in clinical radiation field. The cross calibration formula was modified and the beam quality conversion factor for the experimental values [(k(Q,Q0))field] determined using the modified formula. It's uncertainty was calculated to be 1.9%. The differences between (k(Q,Q0))field of experimental values and k(Q,Q0) for Japan Society of Medical Physics 12 (JSMP12) were 0.73% and 0.88% for 6- and 10-MV photon beams, respectively, remaining within ± 1.9%. This showed k(Q,Q0) for JSMP12 to be consistent with (k(Q,Q0))field of experimental values within the estimated uncertainty range. Although inter-individual differences may be generated, even when the same type of ionized chamber is used, k(Q,Q0) for JSMP12 appears to be consistent within the estimated uncertainty range of (k(Q,Q0)field.

Low-noise quantum frequency down-conversion of indistinguishable photons (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kambs, Benjamin; Kettler, Jan; Bock, Matthias; Becker, Jonas; Arend, Carsten; Jetter, Michael; Michler, Peter; Becher, Christoph

2016-04-01

Single-photon sources based on quantum dots have been shown to exhibit almost ideal properties such as high brightness and purity in terms of clear anti-bunching as well as high two-photon interference visibilities of the emitted photons, making them promising candidates for different quantum information applications such as quantum computing, quantum communication and quantum teleportation. However, as most single-photon sources also quantum dots typically emit light at wavelengths of electronic transitions within the visible or the near infrared range. In order to establish quantum networks with remote building blocks, low-loss single photons at telecom wavelengths are preferable, though. Despite recent progress on emitters of telecom-photons, the most efficient single-photon sources still work at shorter wavelengths. On that matter, quantum frequency down-conversion, being a nonlinear optical process, has been used in recent years to alter the wavelength of single photons to the telecom wavelength range while conserving their nonclassical properties. Characteristics such as lifetime, first-order coherence, anti-bunching and entanglement have been shown to be conserved or even improved due to background suppression during the conversion process, while the conservation of indistinguishability was yet to be shown. Here we present our experimental results on quantum frequency down-conversion of single photons emitted by an InAs/GaAs quantum dot at 903.6 nm following a pulsed excitation of a p-shell exciton at 884 nm. The emitted fluorescence photons are mixed with a strong pump-field at 2155 nm inside a periodically poled lithium niobate ridge waveguide and converted to 1557 nm. Common issues of a large background due to Raman-scattered pump-light photons spectrally overlapping with the converted single photons could largely be avoided, as the pump-wavelength was chosen to be fairly longer than the target wavelength. Additional narrowband spectral filtering at the telecom regime as a result of the small conversion bandwidth and using a high-performance fiber-Bragg-grating solely left the detector dark counts as the only noise source in our setup. Therefore, we could achieve conversion efficiencies of more than 20 %. In order to test the indistinguishability, sequentially emitted photons were fed into a Mach-Zehnder interferometer and spatially as well as temporally overlapped at the output beam splitter. Cross-correlation measurements between both output-ports of the beam splitter exhibit two-photon interference contrasts of more than 40 % prior to and after the down-conversion step. Accordingly, we demonstrate that the process of quantum frequency conversion preserves photon indistinguishability and can be used to establish a versatile source of indistinguishable single photons at the telecom C-Band. Furthermore our scheme allows for converting photons in a wavelength band from 900 nm to 910 nm to the same telecom target wavelength. This enables us to test indistinguishability of frequency-converted photons, originally stemming from different sources with dinstinguishable wavelengths.

Increasing conversion efficiency of two-step photon up-conversion solar cell with a voltage booster hetero-interface.

PubMed

Asahi, Shigeo; Kusaki, Kazuki; Harada, Yukihiro; Kita, Takashi

2018-01-17

Development of high-efficiency solar cells is one of the attractive challenges in renewable energy technologies. Photon up-conversion can reduce the transmission loss and is one of the promising concepts which improve conversion efficiency. Here we present an analysis of the conversion efficiency, which can be increased by up-conversion in a single-junction solar cell with a hetero-interface that boosts the output voltage. We confirm that an increase in the quasi-Fermi gap and substantial photocurrent generation result in a high conversion efficiency.

A solar simulator-pumped atomic iodine laser

NASA Technical Reports Server (NTRS)

Lee, J. H.; Weaver, W. R.

1981-01-01

An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 micron for over 10 ms was obtained for static filling of n-C3F7I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power observed was 4 W for which the system efficiency reached 0.1%. These results indicate that direct solar pumping of a gas laser for power conversion in space is indeed feasible.

Solar power satellite system definition study. Part 1 and part 2, volume 1: Executive summary

NASA Technical Reports Server (NTRS)

1977-01-01

The Solar Power Satellite principle is illustrated and it shows that in a geostationary orbit 36,000 km above the earth's equator, each SPS is in sunlight 99% of the time and in continuous line of sight contact with its ground receiving station. Electrical power produced on the satellite by photovoltaic or heat engine conversion of sunlight is then converted to radio frequency energy at high efficiency, and formed into a focused beam precisely aimed at the SP ground stations. The ground station receiving antenna reconverts the energy into electricity for distribution.

Generation conditions of CW Diode Laser Sustained Plasma

NASA Astrophysics Data System (ADS)

Nishimoto, Koji; Matsui, Makoto; Ono, Takahiro

2016-09-01

Laser sustained plasma was generated using 1 kW class continuous wave diode laser. The laser beam was focused on the seed plasma generated by arc discharge in 1 MPa xenon lamp. The diode laser has advantages of high energy conversion efficiency of 80%, ease of maintenance, compact size and availability of conventional quartz based optics. Therefore, it has a prospect of further development compared with conventional CO2 laser. In this study, variation of the plasma shape caused by laser power is observed and also temperature distribution in the direction of plasma radius is measured by optical emission spectroscopy.

Compact and efficient 2μm Tm:YAP lasers with mechanical or passive Q-switching

NASA Astrophysics Data System (ADS)

Cole, Brian; Goldberg, Lew

2017-02-01

We describe compact and efficient Q-switched diode-pumped, Tm:YAP lasers operating at 1.94μm. Laser CW and Q-switched performance is compared, using both compact mechanical as well as passive Q-switching. For passive Q-switching using a Cr:ZnS saturable absorber (unsaturated transmission of 95%), the laser produced 0.5mJ pulses with an average power of 4.4W and 6.5kW peak power, and had an optical efficiency of 30%. A resonant mirror mechanical Q-switch resulted in a 4 kHz PRF pulse train, with an optical slope efficiency of 52% and an optical-to-optical conversion efficiency of 41%. The laser generated 1.5 mJ, 45 ns FWHM, 33kW peak power pulses, and 6.2W of average output. A second mechanically Q-switched laser operating at 10 kHz PRF produced 1mJ, 35kW peak power pulses, generating 11W average power with an optical efficiency of 46%, and a beam quality of 1.4x diffraction limit.

High power pumped MID-IR wavelength devices using nonlinear frequency mixing (NFM)

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

2001-01-01

Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

High power pumped mid-IR wavelength systems using nonlinear frequency mixing (NFM) devices

NASA Technical Reports Server (NTRS)

Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

1999-01-01

Laser diode pumped mid-IR wavelength systems include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

A review of the Thermoelectronic Laser Energy Converter /TELEC/ Program at Lewis Research Center

NASA Technical Reports Server (NTRS)

Alger, D. L.; Manista, E. J.; Thompson, R. W.

1978-01-01

The investigation of the Thermoelectronic Laser Energy Converter (TELEC) concept at the Lewis Research Center (LeRC) began with a feasibility study of a 1 megawatt sized TELEC system. The TELEC was to use either cesium vapor or hydrogen as the plasma medium. The cesium vapor TELEC appears to be the more practical device studied with an overall calculated conversion efficiency of greater than 48%. Following this study, a small TELEC cell was fabricated which demonstrated the conversion of a small amount of laser power to electrical power. The cell developed a short circuit current of 0.7 amperes and an open circuit voltage, as extrapolated from volt-ampere curves, of about 1.5 volts. Work is now in progress to construct and test a cesium vapor TELEC capable of absorbing 20% of an incident 10 kW, 10.6 micrometer beam, and converting 35% of this power to electrical power.

Temperature-gated thermal rectifier for active heat flow control.

PubMed

Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

2014-08-13

Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (<1%). To the best of our knowledge, this is the first demonstration of solid-state active-thermal devices with a large rectification in the Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.

Simplifications of the RELIEF flow tagging system for laboratory use. [Raman Excitation plus Laser Induced Electronic Fluorescence

NASA Technical Reports Server (NTRS)

Lempert, Walter R.; Zhang, Boying; Miles, Richard B.; Diskin, Glenn

1991-01-01

The use of an O2:He stimulated Raman cell to generate the Stokes beam for the Raman vibrational pumping step of the RELIEF (Raman Excitation plus Laser-Induced Electronic Fluorescence) flow tagging method is reported. Use of the Raman cell rather than a dye laser provides pump and Stokes beams which are automatically frequency matched and temporally and spatially overlapped. The Nd:YAG pump laser is operated multilongitudinal mode, which eliminates the need for injection seeding, resulting in decreased operation complexity and improved stability with respect to acoustic noise. Results are presented for 1st Stokes conversion efficiency and stimulated Brillouin backscattering loss and are compared to the case of pure O2. Scanning CARS measurements of the Q-branch lineshape for both pure O2 and the O2:He mixture are also presented.

Report of a Rare Case: A Maxillary First Molar with Seven Canals Confirmed with Cone-Beam Computed Tomography

PubMed Central

Kumar, Rahul

2014-01-01

Introduction: Coronal anatomic variations in permanent maxillary molars are unusual; conversely variations involving the number of root canals or number of roots are more common. Methods and Materials: This case report presents a successful nonsurgical endodontic therapy of left maxillary first molar with three roots and seven root canals. This unusual morphology was diagnosed using a dental operating microscope (DOM) and confirmed with the help of cone-beam computed tomography (CBCT) images. Results: CBCT axial images showed that both of the palatal and distobuccal roots had Vertucci type II canal pattern, whereas the mesiobuccal root canal showed a Sert and Bayirli’s type XV configuration. Conclusion: The use of a DOM and CBCT imaging in endodontically challenging cases can facilitate a better understanding of the complex root canal anatomy, which ultimately enables the clinician to explore the root canal system, and therefore treat it far more efficiently. PMID:24688587

Terahertz generation by relativistic ponderomotive focusing of two co-axial Gaussian laser beams propagating in ripple density plasma

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

Kumar, Subodh; Singh, Ram Kishor, E-mail: ram007kishor@gmail.com; Sharma, R. P.

Terahertz (THz) generation by beating of two co-axial Gaussian laser beams, propagating in ripple density plasma, has been studied when both ponderomotive and relativistic nonlinearities are operative. When the two lasers co-propagate in rippled density plasma, electrons acquire a nonlinear velocity at beat frequency in the direction transverse to the direction of propagation. This nonlinear oscillatory velocity couples with the density ripple to generate a nonlinear current, which in turn generates THz radiation at the difference frequency. The necessary phase matching condition is provided by the density ripple. Relativistic ponderomotive focusing of the two lasers and its effects on yieldmore » of the generated THz amplitude have been discussed. Numerical results show that conversion efficiency of the order of 10{sup −3} can be achieved in the terahertz radiation generation with relativistic ponderomotive focusing.« less

Optimization of an angle-beam ultrasonic approach for characterization of impact damage in composites

NASA Astrophysics Data System (ADS)

Henry, Christine; Kramb, Victoria; Welter, John T.; Wertz, John N.; Lindgren, Eric A.; Aldrin, John C.; Zainey, David

2018-04-01

Advances in NDE method development are greatly improved through model-guided experimentation. In the case of ultrasonic inspections, models which provide insight into complex mode conversion processes and sound propagation paths are essential for understanding the experimental data and inverting the experimental data into relevant information. However, models must also be verified using experimental data obtained under well-documented and understood conditions. Ideally, researchers would utilize the model simulations and experimental approach to efficiently converge on the optimal solution. However, variability in experimental parameters introduce extraneous signals that are difficult to differentiate from the anticipated response. This paper discusses the results of an ultrasonic experiment designed to evaluate the effect of controllable variables on the anticipated signal, and the effect of unaccounted for experimental variables on the uncertainty in those results. Controlled experimental parameters include the transducer frequency, incidence beam angle and focal depth.

Candidate solar cell materials for photovoltaic conversion in a solar power satellite /SPS/

NASA Technical Reports Server (NTRS)

Glaser, P. E.; Almgren, D. W.

1978-01-01

In recognition of the obstacles to solar-generated baseload power on earth, proposals have been made to locate solar power satellites in geosynchronous earth orbit (GEO), where solar energy would be available 24 hours a day during most of the time of the year. In an SPS, the electricity produced by solar energy conversion will be fed to microwave generators forming part of a planar phase-array transmitting antenna. The antenna is designed to precisely direct a microwave beam of very low intensity to one or more receiving antennas at desired locations on earth. At the receiving antenna, the microwave energy will be safely and efficiently reconverted to electricity and then be transmitted to consumers. An SPS system will include a number of satellites in GEO. Attention is given to the photovoltaic option for solar energy conversion in GEO, solar cell requirements, the availability of materials, the implication of large production volumes, requirements for high-volume manufacture of solar cell arrays, and the effects of concentration ratio on solar cell array area.

High efficiency and good beam quality of electro-optic, cavity-dumped and double-end pumped Nd:YLF laser

NASA Astrophysics Data System (ADS)

Tang, X. X.; Fan, Z. W.; Qiu, J. S.; Lian, F. Q.; Zhang, X. L.

2012-06-01

In this paper, we describe a Nd:YLF laser based on high-speed RTP electro-optical cavity dumping technique. Two home-made 150 W fiber pump modules are used from both sides to pump Nd:YLF crystal. Coupling systems are the key elements in end-pumped solid-state lasers, the aberrations of which greatly affect the efficiency of the lasers. In order to get high efficient and good quality laser output, the optical software ZEMAX is used to design a four-piece coupling system. When the pumped energy is 32 mJ at the repetition rate of 1 Hz, the output energy is 6.5 mJ with 2.5 ns pulse width. When the pumped energy is 13.1 W at the repetition rate of 200 Hz, the output energy is 2.2 W with small M 2 factor where M {/x 2} is 1.04, and M {/y 2} is 1.05, and the light-light conversion efficiency is up to 16.8%.

Technique Developed for Optimizing Traveling-Wave Tubes

NASA Technical Reports Server (NTRS)

Wilson, Jeffrey D.

1999-01-01

A traveling-wave tube (TWT) is an electron beam device that is used to amplify electromagnetic communication waves at radio and microwave frequencies. TWT s are critical components in deep-space probes, geosynchronous communication satellites, and high-power radar systems. Power efficiency is of paramount importance for TWT s employed in deep-space probes and communications satellites. Consequently, increasing the power efficiency of TWT s has been the primary goal of the TWT group at the NASA Lewis Research Center over the last 25 years. An in-house effort produced a technique (ref. 1) to design TWT's for optimized power efficiency. This technique is based on simulated annealing, which has an advantage over conventional optimization techniques in that it enables the best possible solution to be obtained (ref. 2). A simulated annealing algorithm was created and integrated into the NASA TWT computer model (ref. 3). The new technique almost doubled the computed conversion power efficiency of a TWT from 7.1 to 13.5 percent (ref. 1).

Defective TiO 2 with high photoconductive gain for efficient and stable planar heterojunction perovskite solar cells

DOE PAGES

Li, Yanbo; Cooper, Jason K.; Liu, Wenjun; ...

2016-08-18

Formation of planar heterojunction perovskite solar cells exhibiting both high efficiency and stability under continuous operation remains a challenge. Here, we show this can be achieved by using a defective TiO 2 thin film as the electron transport layer. TiO 2 layers with native defects are deposited by electron beam evaporation in an oxygen-deficient environment. Deep-level hole traps are introduced in the TiO 2 layers and contribute to a high photoconductive gain and reduced photocatalytic activity. The high photoconductivity of the TiO 2 electron transport layer leads to improved efficiency for the fabricated planar devices. A maximum power conversion efficiencymore » of 19.0% and an average PCE of 17.5% are achieved. In addition, the reduced photocatalytic activity of the TiO 2 layer leads to enhanced long-Term stability for the planar devices. Under continuous operation near the maximum power point, an efficiency of over 15.4% is demonstrated for 100 h.« less

Enhanced proton acceleration in an applied longitudinal magnetic field

DOE PAGES

Arefiev, A.; Toncian, T.; Fiksel, G.

2016-10-31

Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the lasermore » energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.« less

Analysis of Hybrid Type Boron-Doped Carbon Stripper Foils in J-PARC RCS

NASA Astrophysics Data System (ADS)

Yamazaki, Y.; Yoshimoto, M.; Takeda, O.; Kinsho, M.; Taguchi, T.; Yamamoto, S.; Kurihara, T.; Sugai, I.

2013-03-01

J-PARC (Japan-Proton Accelerator Research Complex) requires a carbon stripper foil to strip electrons from the H- beam supplied by the linac before injection into the Rapid Cycling Synchrotron (RCS) [1]. The foil thickness is about μm (200μg/cm2) corresponding to conversion efficiency of 99.7% from the primary H- beams of 181MeV energy to H+. We have successfully developed the Hybrid type thick Boron-doped Carbon (HBC) stripper foil, which showed a drastic improvement the lifetime without thickness reduction and shrinkage at the irradiated area. We started to study carbon stripper foils microscopically why carbon foils have considerable endurance for the beam impact by boron-doped. At first step, we made a comparison of ion irradiation effect between normal carbon and HBC by the electric microscope, ion-induced analysis. In particular, it seems that grain size of boron-rich area became much larger by irradiation for HBC. It was also observed that the boron-rich grain grew up by taking around material and generated pinholes more than 100 nm near itself consequently.

Enhanced proton acceleration in an applied longitudinal magnetic field

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

Arefiev, A.; Toncian, T.; Fiksel, G.

Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the lasermore » energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.« less

Two-Photon Ghost Image and Interference-Diffraction

NASA Technical Reports Server (NTRS)

Shih, Y. H.; Sergienko, A. V.; Pittman, T. B.; Strekalov, D. V.; Klyshko, D. N.

1996-01-01

One of the most surprising consequences of quantum mechanics is entanglement of two or more distance particles. The two-particle entangled state was mathematically formulated by Schrodinger. Based on this unusual quantum behavior, EPR defined their 'physical reality' and then asked the question: 'Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?' One may not appreciate EPR's criterion of physical reality and insist that 'no elementary quantum phenomenon is a phenomenon until it is a recorded phenomenon'. Optical spontaneous parametric down conversion (SPDC) is the most effective mechanism to generate an EPR type entangled two-photon state. In SPDC, an optical beam, called the pump, is incident on a birefringent crystal. The pump is intense enough so that nonlinear effects lead to the conversion of pump photons into pairs of photons, historically called signal and idler. Technically, the SPDC is said to be type-1 or type-2, depending on whether the signal and idler beams have parallel or orthogonal polarization. The SPDC conversion efficiency is typically on the order of 10(exp -9) to 10(exp -11), depending on the SPDC nonlinear material. The signal and idler intensities are extremely low, only single photon detection devices can register them. The quantum entanglement nature of SPDC has been demonstrated in EPR-Bohm experiments and Bell's inequality measurements. The following two experiments were recently performed in our laboratory, which are more closely related to the original 1935 EPR gedankenezperiment. The first experiment is a two-photon optical imaging type experiment, which has been named 'ghost image' by the physics community. The signal and idler beams of SPDC are sent in different directions, so that the detection of the signal and idler photons can be performed by two distant photon counting detectors. An aperture object (mask) is placed in front of the signal photon detector and illuminated by the signal beam through a convex lens. Surprisingly, an image of this aperture is observed in the idler beam, by scanning the idler photon detector in the transverse plane of the idler beam, if we are sure that the idler photon detector 'catches' the 'twin brother' of the signal, which can be easily performed by a coincidence measurement. This effect is even more striking when we found that the object-lens-image relationship satisfies the Gaussian thin lens equation. The second experiment demonstrates two-photon 'ghost' interference-diffraction. The experimental set up is similar to the image experiment, except that rather than a lens and an aperture it is a Young's double-slit (or a single-slit) inserted into the path of the signal beam. We could not find any interference (or diffraction) pattern behind the slit. Surprisingly, an interference (or diffraction) pattern is observed when scanning the detector in the idler beam, if we are sure that the idler photon detector 'catches' the 'twin brother' of the signal.

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

Renaud, James, E-mail: james.renaud@mail.mcgill.ca; Seuntjens, Jan; Sarfehnia, Arman

Purpose: In this work, the authors describe an electron sealed water calorimeter (ESWcal) designed to directly measure absorbed dose to water in clinical electron beams and its use to derive electron beam quality conversion factors for two ionization chamber types. Methods: A functioning calorimeter prototype was constructed in-house and used to obtain reproducible measurements in clinical accelerator-based 6, 9, 12, 16, and 20 MeV electron beams. Corrections for the radiation field perturbation due to the presence of the glass calorimeter vessel were calculated using Monte Carlo (MC) simulations. The conductive heat transfer due to dose gradients and nonwater materials wasmore » also accounted for using a commercial finite element method software package. Results: The relative combined standard uncertainty on the ESWcal dose was estimated to be 0.50% for the 9–20 MeV beams and 1.00% for the 6 MeV beam, demonstrating that the development of a water calorimeter-based standard for electron beams over such a wide range of clinically relevant energies is feasible. The largest contributor to the uncertainty was the positioning (Type A, 0.10%–0.40%) and its influence on the perturbation correction (Type B, 0.10%–0.60%). As a preliminary validation, measurements performed with the ESWcal in a 6 MV photon beam were directly compared to results derived from the National Research Council of Canada (NRC) photon beam standard water calorimeter. These two independent devices were shown to agree well within the 0.43% combined relative uncertainty of the ESWcal for this beam type and quality. Absorbed dose electron beam quality conversion factors were measured using the ESWcal for the Exradin A12 and PTW Roos ionization chambers. The photon-electron conversion factor, k{sub ecal}, for the A12 was also experimentally determined. Nonstatistically significant differences of up to 0.7% were found when compared to the calculation-based factors listed in the AAPM’s TG-51 protocol. General agreement between the relative electron energy dependence of the PTW Roos data measured in this work and a recent MC-based study are also shown. Conclusions: This is the first time that water calorimetry has been successfully used to measure electron beam quality conversion factors for energies as low as 6 MeV (R{sub 50} = 2.25 cm)« less

Energy harvesting from controlled buckling of piezoelectric beams

NASA Astrophysics Data System (ADS)

Ansari, M. H.; Karami, M. Amin

2015-11-01

A piezoelectric vibration energy harvester is presented that can generate electricity from the weight of passing cars or crowds. The energy harvester consists of a piezoelectric beam, which buckles when the device is stepped on. The energy harvester can have a horizontal or vertical configuration. In the vertical (direct) configuration, the piezoelectric beam is vertical and directly sustains the weight of the vehicles or people. In the horizontal (indirect) configuration, the vertical weight is transferred to a horizontal axial force through a scissor-like mechanism. Buckling of the beam results in significant stresses and, thus, large power production. However, if the beam’s buckling is not controlled, the beam will fracture. To prevent this, the axial deformation is constrained to limit the deformations of the beam. In this paper, the energy harvester is analytically modeled. The considered piezoelectric beam is a general non-uniform beam. The natural frequencies, mode shapes, and the critical buckling force corresponding to each mode shape are calculated. The electro-mechanical coupling and the geometric nonlinearities are included in the model. The design criteria for the device are discussed. It is demonstrated that a device, realized with commonly used piezoelectric patches, can generate tens of milliwatts of power from passing car traffic. The proposed device could also be implemented in the sidewalks or integrated in shoe soles for energy generation. One of the key features of the device is its frequency up-conversion characteristics. The piezoelectric beam undergoes free vibrations each time the weight is applied to or removed from the energy harvester. The frequency of the free vibrations is orders of magnitude larger than the frequency of the load. The device is, thus, both efficient and insensitive to the frequency of the force excitations.

Optimization of pencil beam f-theta lens for high-accuracy metrology

NASA Astrophysics Data System (ADS)

Peng, Chuanqian; He, Yumei; Wang, Jie

2018-01-01

Pencil beam deflectometric profilers are common instruments for high-accuracy surface slope metrology of x-ray mirrors in synchrotron facilities. An f-theta optical system is a key optical component of the deflectometric profilers and is used to perform the linear angle-to-position conversion. Traditional optimization procedures of the f-theta systems are not directly related to the angle-to-position conversion relation and are performed with stops of large size and a fixed working distance, which means they may not be suitable for the design of f-theta systems working with a small-sized pencil beam within a working distance range for ultra-high-accuracy metrology. If an f-theta system is not well-designed, aberrations of the f-theta system will introduce many systematic errors into the measurement. A least-squares' fitting procedure was used to optimize the configuration parameters of an f-theta system. Simulations using ZEMAX software showed that the optimized f-theta system significantly suppressed the angle-to-position conversion errors caused by aberrations. Any pencil-beam f-theta optical system can be optimized with the help of this optimization method.

Efficient green lasers for high-resolution scanning micro-projector displays

NASA Astrophysics Data System (ADS)

Bhatia, Vikram; Bauco, Anthony S.; Oubei, Hassan M.; Loeber, David A. S.

2010-02-01

Laser-based projectors are gaining increased acceptance in mobile device market due to their low power consumption, superior image quality and small size. The basic configuration of such micro-projectors is a miniature mirror that creates an image by raster scanning the collinear red, blue and green laser beams that are individually modulated on a pixel-bypixel basis. The image resolution of these displays can be limited by the modulation bandwidth of the laser sources, and the modulation speed of the green laser has been one of the key limitations in the development of these displays. We will discuss how this limitation is fundamental to the architecture of many laser designs and then present a green laser configuration which overcomes these difficulties. In this green laser architecture infra-red light from a distributed Bragg-reflector (DBR) laser diode undergoes conversion to green light in a waveguided second harmonic generator (SHG) crystal. The direct doubling in a single pass through the SHG crystal allows the device to operate at the large modulation bandwidth of the DBR laser. We demonstrate that the resultant product has a small footprint (<0.7 cc envelope volume), high efficiency (>9% electrical-to-optical conversion) and large modulation bandwidth (>100 MHz).

A millimeter wave relativistic backward wave oscillator operating in TM{sub 03} mode with low guiding magnetic field

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

Ye, Hu; Wu, Ping; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an Shaanxi 710024

2015-06-15

A V-band overmoded relativistic backward wave oscillator (RBWO) guided by low magnetic field and operating on a TM{sub 03} mode is presented to increase both the power handling capacity and the wave-beam interaction conversion efficiency. Trapezoidal slow wave structures (SWSs) with shallow corrugations and long periods are adopted to make the group velocity of TM{sub 03} mode at the intersection point close to zero. The coupling impedance and diffraction Q-factor of the RBWO increase, while the starting current decreases owing to the reduction of the group velocity of TM{sub 03} mode. In addition, the TM{sub 03} mode dominates over themore » other modes in the startup of the oscillation. Via numerical simulation, the generation of the microwave pulse with an output power of 425 MW and a conversion efficiency of 32% are achieved at 60.5 GHz with an external magnetic field of 1.25 T. This RBWO can provide greater power handling capacity when operating on the TM{sub 03} mode than on the TM{sub 01} mode.« less

300 mW of coherent light at 488 nm using a generic approach

NASA Astrophysics Data System (ADS)

Karamehmedović, Emir; Pedersen, Christian; Andersen, Martin T.; Tidemand-Lichtenberg, Peter

2008-02-01

We present a generic approach for efficient generation of CW light with a predetermined wavelength within the visible or UV spectrum. Based on sum-frequency generation (SFG), the circulating intra-cavity field of a high-finesse diode pumped CW solid-state laser (DPSSL) and the output from a tapered, single-frequency external cavity diode laser (ECDL) are mixed inside a 10 mm periodically poled KTP crstal (pp-KTP). The pp-KTP is situated inside the DPSSL cavity to enhance conversion efficiency of the nonlinear mixing process. This approach combines different solid state technologies; the tuneability of ECDLs, the high intra-cavity filed of DPSSLs and flexible quasi phase matching in pp-tapered ECDL with a center wavelength of 766 nm in combination with a high finesse Nd:YVo4 laser at 1342 nm. Up to 308 mW of light at 488nm was measured in our experiments. The conversion of te ECDL beam was up to 47% after it was transmitted through a PM fiber, and up to 32% without fiber coupling. Replacing the seed laser and the nonlinear crystal makes it possible to generate light at virtually any desired wavelength withing the visible spectrum.

Development and investigation of silicon converter beta radiation 63Ni isotope

NASA Astrophysics Data System (ADS)

Krasnov, A. A.; Legotin, S. A.; Murashev, V. N.; Didenko, S. I.; Rabinovich, O. I.; Yurchuk, S. Yu; Omelchenko, Yu K.; Yakimov, E. B.; Starkov, V. V.

2016-02-01

In this paper the results of the creation and researching characteristics of, experimental betavoltaic converters (BVC), based on silicon are discussed. It was presented the features of structural and technological performance of planar 2 D- structure of BVC. To study the parameters of the converter stream the beta particles of the radioisotope was simulated by 63Ni electron flux from scanning electron microscope. It was investigated the dependence of the collecting electrons efficiency from the beam energy current-voltage characteristic was measured when irradiated by an electron beam, from which the value of the short-circuit current density equal to 126 nA / cm2 and the value of the open circuit voltage of 150 mV were obtained. The maximum power density at 70 mV is 9.5 nW / cm2, and the conversion efficiency is 2.1%. It was presented the results of experimental studies of the current-voltage characteristics of samples by irradiating a film 63Ni. The values of load voltage 111 mV and short circuit current density of 27 nA / cm2 were obtained. Maximum power density was 1.52 nW / cm2.

A 57GHz overmoded coaxial relativistic backward wave oscillator with high conversion efficiency and pure TM01 mode output

NASA Astrophysics Data System (ADS)

Chen, Siyao; Zhang, Jun; Bai, Zhen

2017-10-01

A 57GHz overmoded relativistic backward wave oscillator (RBWO) operating on the quasi-TEM mode with pure TM01 mode output is presented in this paper, by using outer trapezoidal slow wave structure (SWS) with large distance between inner and outer conductors. The large overmoded ratio can be obtained in coaxial devices to improve power handling capacity, while the large distance between inner and outer conductors can guarantee the electron beam transmit effectively. The 8π/9 mode of quasi-TEM synchronously interacts with the electron beam, while the TM01 mode diffracted by the quasi-TEM mode outputs. The existence of TM01 6π/9 mode in SWS can extract energy from the quasi-TEM mode (which has a high value of Qe) thus increasing the power handling capacity. Particle-in-cell simulation shows that generation with high power 560 MW and efficiency 43.5% is obtained under the diode voltage 520 kV and current 2.47 kA. And the microwave has the pure frequency spectrum of 56.8 GHz radiates in the pure TM01 mode (about 98%).

Design and 3D simulation of a two-cavity wide-gap relativistic klystron amplifier with high power injection

NASA Astrophysics Data System (ADS)

Bai, Xianchen; Yang, Jianhua; Zhang, Jiande

2012-08-01

By using an electromagnetic particle-in-cell (PIC) code, an S-band two-cavity wide-gap klystron amplifier (WKA) loaded with washers/rods structure is designed and investigated for high power injection application. Influences of the washers/rods structure on the high frequency characteristics and the basic operation of the amplifier are presented. Generally, the rod structure has great impacts on the space-charge potential depression and the resonant frequency of the cavities. Nevertheless, if only the resonant frequency is tuned to the desired operation frequency, effects of the rod size on the basic operation of the amplifier are expected to be very weak. The 3-dimension (3-D) PIC simulation results show an output power of 0.98 GW corresponding to an efficiency of 33% for the WKA, with a 594 keV, 5 kA electron beam guided by an external magnetic field of 1.5 Tesla. Moreover, if a conductive plane is placed near the output gap, such as the electron collector, the beam potential energy can be further released, and the RF power can be increased to about 1.07 GW with the conversion efficiency of about 36%.

A High-Power Broadband Terahertz Source Enabled by Three-Dimensional Light Confinement in a Plasmonic Nanocavity.

PubMed

Yardimci, Nezih Tolga; Cakmakyapan, Semih; Hemmati, Soroosh; Jarrahi, Mona

2017-06-23

The scope and potential uses of time-domain terahertz imaging and spectroscopy are mainly limited by the low optical-to-terahertz conversion efficiency of photoconductive terahertz sources. State-of-the-art photoconductive sources utilize short-carrier-lifetime semiconductors to recombine carriers that cannot contribute to efficient terahertz generation and cause additional thermal dissipation. Here, we present a novel photoconductive terahertz source that offers a significantly higher efficiency compared with terahertz sources fabricated on short-carrier-lifetime substrates. The key innovative feature of this source is the tight three-dimensional confinement of the optical pump beam around the terahertz nanoantennas that are used as radiating elements. This is achieved by means of a nanocavity formed by plasmonic structures and a distributed Bragg reflector. Consequently, almost all of the photo-generated carriers can be routed to the terahertz nanoantennas within a sub-picosecond time-scale. This results in a very strong, ultrafast current that drives the nanoantennas to produce broadband terahertz radiation. We experimentally demonstrate that this terahertz source can generate 4 mW pulsed terahertz radiation under an optical pump power of 720 mW over the 0.1-4 THz frequency range. This is the highest reported power level for terahertz radiation from a photoconductive terahertz source, representing more than an order of magnitude of enhancement in the optical-to-terahertz conversion efficiency compared with state-of-the-art photoconductive terahertz sources fabricated on short-carrier-lifetime substrates.

A High-Power Broadband Terahertz Source Enabled by Three-Dimensional Light Confinement in a Plasmonic Nanocavity

DOE PAGES

Yardimci, Nezih Tolga; Cakmakyapan, Semih; Hemmati, Soroosh; ...

2017-06-23

The scope and potential uses of time-domain terahertz imaging and spectroscopy are mainly limited by the low optical-to-terahertz conversion efficiency of photoconductive terahertz sources. State-of-theart photoconductive sources utilize short-carrier-lifetime semiconductors to recombine carriers that cannot contribute to efficient terahertz generation and cause additional thermal dissipation. Here, we present a novel photoconductive terahertz source that offers a significantly higher efficiency compared with terahertz sources fabricated on short-carrier-lifetime substrates. The key innovative feature of this source is the tight three-dimensional confinement of the optical pump beam around the terahertz nanoantennas that are used as radiating elements. This is achieved by means ofmore » a nanocavity formed by plasmonic structures and a distributed Bragg reflector. Consequently, almost all of the photo-generated carriers can be routed to the terahertz nanoantennas within a sub-picosecond time-scale. This results in a very strong, ultrafast current that drives the nanoantennas to produce broadband terahertz radiation. We experimentally demonstrate that this terahertz source can generate 4 mW pulsed terahertz radiation under an optical pump power of 720 mW over the 0.1–4 THz frequency range. This is the highest reported power level for terahertz radiation from a photoconductive terahertz source, representing more than an order of magnitude of enhancement in the optical-to-terahertz conversion efficiency compared with state-of-the-art photoconductive terahertz sources fabricated on shortcarrier- lifetime substrates.« less

Electro-optic voltage sensor with Multiple Beam Splitting

DOEpatents

Woods, Gregory K.; Renak, Todd W.; Crawford, Thomas M.; Davidson, James R.

2000-01-01

A miniature electro-optic voltage sensor system capable of accurate operation at high voltages without use of the dedicated voltage dividing hardware. The invention achieves voltage measurement without significant error contributions from neighboring conductors or environmental perturbations. The invention employs a transmitter, a sensor, a detector, and a signal processor. The transmitter produces a beam of electromagnetic radiation which is routed into the sensor. Within the sensor the beam undergoes the Pockels electro-optic effect. The electro-optic effect produces a modulation of the beam's polarization, which is in turn converted to a pair of independent conversely-amplitude-modulated signals, from which the voltage of the E-field is determined by the signal processor. The use of converse AM signals enables the signal processor to better distinguish signal from noise. The sensor converts the beam by splitting the beam in accordance with the axes of the beam's polarization state (an ellipse) into at least two AM signals. These AM signals are fed into a signal processor and processed to determine the voltage between a ground conductor and the conductor on which voltage is being measured.

Imaging RF Phased Array Receivers using Optically-Coherent Up-conversion for High Beam-Bandwidth Processing

DTIC Science & Technology

2017-03-01

It does so by using an optical lens to perform an inverse spatial Fourier Transform on the up-converted RF signals, thereby rendering a real-time... simultaneous beams or other engineered beam patterns. There are two general approaches to array-based beam forming: digital and analog. In digital beam...of significantly limiting the number of beams that can be formed simultaneously and narrowing the operational bandwidth. An alternate approach that

Experimental observation of spatial quantum noise reduction below the standard quantum limit with bright twin beams of light

NASA Astrophysics Data System (ADS)

Kumar, Ashok; Nunley, Hayden; Marino, Alberto

2016-05-01

Quantum noise reduction (QNR) below the standard quantum limit (SQL) has been a subject of interest for the past two to three decades due to its wide range of applications in quantum metrology and quantum information processing. To date, most of the attention has focused on the study of QNR in the temporal domain. However, many areas in quantum optics, specifically in quantum imaging, could benefit from QNR not only in the temporal domain but also in the spatial domain. With the use of a high quantum efficiency electron multiplier charge coupled device (EMCCD) camera, we have observed spatial QNR below the SQL in bright narrowband twin light beams generated through a four-wave mixing (FWM) process in hot rubidium atoms. Owing to momentum conservation in this process, the twin beams are momentum correlated. This leads to spatial quantum correlations and spatial QNR. Our preliminary results show a spatial QNR of over 2 dB with respect to the SQL. Unlike previous results on spatial QNR with faint and broadband photon pairs from parametric down conversion (PDC), we demonstrate spatial QNR with spectrally and spatially narrowband bright light beams. The results obtained will be useful for atom light interaction based quantum protocols and quantum imaging. Work supported by the W.M. Keck Foundation.

Recent Progress Made in the Development of High-Energy UV Transmitter

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Armstrong, Darrell J.

2007-01-01

In this paper, the status of an all-solid-state UV converter development for ozone sensing applications is discussed. A high energy Nd:YAG laser for pumping the UV converter arrangement was recently reported. The pump is an all-solid-state, single longitudinal mode, and conductively cooled Nd:YAG laser operating at 1064 nm wavelength. Currently, this pump laser provides an output pulse energy of greater than 1J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of approx. 2. The spatial profile of the output beam is a rectangular super Gaussian. This Nd:YAG pump laser has been developed to pump the nonlinear optics based UV converter arrangement to generate 320 nm and 308 nm wavelengths by means of 532 nm wavelength. Previously, this UV converter arrangement has demonstrated IR-to-UV conversion efficiency of 24% using a flash lamp pumped laser providing a round, flat top spatial profile. Recently, the UV converter was assembled and tested at NASA LaRC for pumping with the diode pumped Nd:YAG laser. With current spatial profile, the UV converter was made operational. Current efforts to maximize the nonlinear conversion efficiency by refining its spatial profile to match RISTRA OPO requirements are progressing.

Report on the Failure of Roof Beams at Sir John Cass's Foundation and Red Coat Church of England Secondary School, Stepney. Building Research Establishment Current Paper 58/74.

ERIC Educational Resources Information Center

Bate, S. C. C.

Two beams forming part of the roof over the swimming pool at the school collapsed. The investigation showed that the cause of the failure was loss of strength due to conversion of high alumina cement concrete followed by sulphate attack leading to disruption of the concrete. The degree of conversion and loss of strength was greater than expected…

Experimental preparation of the Werner state via spontaneous parametric down-conversion

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

Zhang Yongsheng; Huang Yunfeng; Li Chuanfeng

2002-12-01

We present an experiment for preparing a Werner state via spontaneous parametric down-conversion and controlled decoherence of photons in this paper. In this experiment two independent {beta}-barium borate crystals are used to produce down-conversion light beams, which are mixed to prepare the Werner state.

Cavity-enhanced frequency doubling from 795nm to 397.5nm ultra-violet coherent radiation with PPKTP crystals in the low pump power regime.

PubMed

Wen, Xin; Han, Yashuai; Bai, Jiandong; He, Jun; Wang, Yanhua; Yang, Baodong; Wang, Junmin

2014-12-29

We demonstrate a simple, compact and cost-efficient diode laser pumped frequency doubling system at 795 nm in the low power regime. In two configurations, a bow-tie four-mirror ring enhancement cavity with a PPKTP crystal inside and a semi-monolithic PPKTP enhancement cavity, we obtain 397.5nm ultra-violet coherent radiation of 35mW and 47mW respectively with a mode-matched fundamental power of about 110mW, corresponding to a conversion efficiency of 32% and 41%. The low loss semi-monolithic cavity leads to the better results. The constructed ultra-violet coherent radiation has good power stability and beam quality, and the system has huge potential in quantum optics and cold atom physics.

Ecological conversion efficiency and its influencers in twelve species of fish in the Yellow Sea Ecosystem

NASA Astrophysics Data System (ADS)

Tang, Qisheng; Guo, Xuewu; Sun, Yao; Zhang, Bo

2007-09-01

The ecological conversion efficiencies in twelve species of fish in the Yellow Sea Ecosystem, i.e., anchovy ( Engraulis japonicus), rednose anchovy ( Thrissa kammalensis), chub mackerel ( Scomber japonicus), halfbeak ( Hyporhamphus sajori), gizzard shad ( Konosirus punctatus), sand lance ( Ammodytes personatus), red seabream ( Pagrus major), black porgy ( Acanthopagrus schlegeli), black rockfish ( Sebastes schlegeli), finespot goby ( Chaeturichthys stigmatias), tiger puffer ( Takifugu rubripes), and fat greenling ( Hexagrammos otakii), were estimated through experiments conducted either in situ or in a laboratory. The ecological conversion efficiencies were significantly different among these species. As indicated, the food conversion efficiencies and the energy conversion efficiencies varied from 12.9% to 42.1% and from 12.7% to 43.0%, respectively. Water temperature and ration level are the main factors influencing the ecological conversion efficiencies of marine fish. The higher conversion efficiency of a given species in a natural ecosystem is acquired only under the moderate environment conditions. A negative relationship between ecological conversion efficiency and trophic level among ten species was observed. Such a relationship indicates that the ecological efficiency in the upper trophic levels would increase after fishing down marine food web in the Yellow Sea ecosystem.

Design, construction and evaluation of a 12.2 GHz, 4.0 kW-CW coupled-cavity traveling wave tube

NASA Technical Reports Server (NTRS)

Ayers, W. R.; Harman, W. A.

1973-01-01

An analytical and experimental program to study design techniques and to utilize these techniques to optimize the performance of an X-band 4 kW, CW traveling wave tube ultimately intended for satellite-borne television broadcast transmitters is described. The design is based on the coupled-cavity slow-wave circuit with velocity resynchronization to maximize the conversion efficiency. The design incorporates a collector which is demountable from the tube. This was done to facilitate multistage depressed collector experiments employing a NASA designed axisymmetric, electrostatic collector for linear beam microwave tubes after shipment of the tubes to NASA.

High-power single-pass pumped diamond Raman oscillator

NASA Astrophysics Data System (ADS)

Heinzig, Matthias; Walbaum, Till; Williams, Robert J.; Kitzler, Ondrej; Mildren, Richard P.; Schreiber, Thomas; Eberhardt, Ramona; Tünnermann, Andreas

2018-02-01

We present our recent advances on power scaling of a high-power single-pass pumped CVD-diamond Raman oscillator at 1.2 μm. The single pass scheme reduced feedback to the high gain fiber amplifier, which pumps the oscillator. The Yb-doped multi-stage fiber amplifier itself enables up to 1 kW output power at a narrow linewidth of 0.16 nm. We operate this laser in quasi-cw mode at 10% duty cycle and on-time (pulse) duration of 10 ms. With a maximum conversion efficiency of 39%, a maximum steady-state output power of 380 W and diffraction limited beam quality was achieved.

Demonstration of high-energy 2 omega (526.5 nm) operation on the National Ignition Facility Laser System.

PubMed

Heestand, G M; Haynam, C A; Wegner, P J; Bowers, M W; Dixit, S N; Erbert, G V; Henesian, M A; Hermann, M R; Jancaitis, K S; Knittel, K; Kohut, T; Lindl, J D; Manes, K R; Marshall, C D; Mehta, N C; Menapace, J; Moses, E; Murray, J R; Nostrand, M C; Orth, C D; Patterson, R; Sacks, R A; Saunders, R; Shaw, M J; Spaeth, M; Sutton, S B; Williams, W H; Widmayer, C C; White, R K; Whitman, P K; Yang, S T; Van Wonterghem, B M

2008-07-01

A single beamline of the National Ignition Facility (NIF) has been operated at a wavelength of 526.5 nm (2 omega) by frequency converting the fundamental 1053 nm (1 omega) wavelength with an 18.2 mm thick type-I potassium dihydrogen phosphate (KDP) second-harmonic generator (SHG) crystal. Second-harmonic energies of up to 17.9 kJ were measured at the final optics focal plane with a conversion efficiency of 82%. For a similarly configured 192-beam NIF, this scales to a total 2 omega energy of 3.4 MJ full NIF equivalent (FNE).

High-Power Nd:GdVO4 Innoslab Continuous-Wave Laser under Direct 880 nm Pumping

NASA Astrophysics Data System (ADS)

Deng, Bo; Zhang, Heng-Li; Xu, Liu; Mao, Ye-Fei; He, Jing-Liang; Xin, Jian-Guo

2014-11-01

A high-power cw end-pumped laser device is demonstrated with a slab crystal of Nd:GdVO4 operating at 1063 nm. Diode laser stacks at 880 nm are used to pump Nd:GdVO4 into emitting level 4F3/2. The 149 W output power is presented when the absorbed pump power is 390 W and the optical-to-optical conversion efficiency is 38.2%. When the output power is 120 W, the M2 factors are 2.3 in both directions. Additionally, mode overlap inside the resonator is analyzed to explain the beam quality deterioration.

36 W Q-switched Ho:YAG laser at 2097 nm pumped by a Tm fiber laser: evaluation of different Ho3+ doping concentrations

NASA Astrophysics Data System (ADS)

Antipov, O. L.; Eranov, I. D.; Kositsyn, R. I.

2017-01-01

A laser oscillator based on Ho:YAG crystal pumped by a Tm fiber laser with an acousto-optical Q-switch was optimized for maximum output power and pulse-to-pulse stability. Stable operation at 2097 nm in Q-switched mode is demonstrated, with pulse repetition rates from 10 to 30 kHz, and output power of 36 W (at 55 W of pump power at 1908 nm) in the good quality beam. The influence of Ho ion up-conversion and thermal lensing on the oscillation efficiency is discussed.

Efficient high-power narrow-linewidth all-fibred linearly polarized ytterbium laser source

NASA Astrophysics Data System (ADS)

Bertrand, Anthony; Liégeois, Flavien; Hernandez, Yves; Giannone, Domenico

2012-06-01

We report on experimental results on a high power, all-fibred, linearly polarized, mode-locked laser at 1.03 μm. The laser generates pulses of 40 ps wide at a repetition rate of 52 MHz, exhibiting 12 kW peak power. Dispersion in optical fibres is controlled to obtain both high power and narrow spectral linewidth. The average output power reached is 25 W with a spectral linewidth of 380 pm and a near diffraction limit beam (M2 < 1.2). This laser is an ideal candidate for applications like IR spectroscopy, where high peak power and narrow linewidth are required for subsequent wavelength conversion.

Laser-plasma interactions from thin tapes for high-energy electron accelerators and seeding compact FELs

NASA Astrophysics Data System (ADS)

Shaw, Brian Henry

This thesis comprises a detailed investigation of the physics of using a plasma mirror (PM) from a tape by reflecting ultrashort pulses from a laser-triggered surface plasma. The tapes used in the characterization of the PM are VHS and computer data storage tape. The tapes are 6.6 m (computer storage tape) and 15 m (VHS) thick. Each tape is 0.5 inches wide, and 10s of meters of tape are spooled using a tape drive; providing thousands of shots on a single reel of tape. The amount of reflected energy of the PM was studied for different input intensities. The fluence was varied by translating the focus of the laser upstream and downstream of the tape, which changed the spot size on the tape surface and hence changed the fluence. This study measured reflectances from both sides of the two tapes, and for input light of both s and p-polarizations. Lastly, an analytic model was developed to understand the reflectance as a function of fluence for each tape material and polarization. Another application that benefits from the advancements of LPA technology is an LPAbased FEL. By sending a high quality electron bunch through an undulator (a periodic structure of positive and negative magnetic poles), the electrons oscillate transversely to the propagation axis and produce radiation. The 1.5 m THUNDER undulator at the BELLA Center has been commissioned using electron beams of 400MeV beams with broad energy spread (35%). To produce a coherent LPA-based FEL, the beam quality would need to improve to sub-percent level energy spread. A seed source could be used to help induce bunching of the electron beam within the undulator. This thesis described the experimental investigation of the physics of using solid-based surface high-harmonic generation (SHHG) from a thin tape as a possible seed source for an FEL. A thin tape placed within centimeters of the undulator's entrance could act as a harmonic generating source, while simultaneously transmitting an electron beam. This removes the need for transport optics for the XUV photons and the need for additional optics to overlap the seed beam with the electron beam at the undulator entrance. By operating at sub-relativistic laser strengths, harmonics up to the 17th order of 800 nm light are produced using an SHHG technique known as coherent wake emission (CWE). CWE pulse properties such as divergence, energy, conversion efficiency, and spectrum are measured for a wide range of tape materials and drive laser conditions. A clear correlation between surface roughness and harmonic beam divergence is found. The measured pulse properties for the 15th harmonic from VHS tape (conversion efficiency 6.5x10-7 and an rms divergence of 12 mrad), the 100 mJ-level, 40-50 fs-class drive laser, produces peak powers of several MW's of XUV pulses. The results of a 1D model indicate that these CWE pulses with MW level powers are sufficient for seed-induced FEL gain. (Abstract shortened by ProQuest.).

Real World Testing Of A Piezoelectric Rotational Energy Harvester For Human Motion

NASA Astrophysics Data System (ADS)

Pillatsch, P.; Yeatman, E. M.; Holmes, A. S.

2013-12-01

Harvesting energy from human motion is challenging because the frequencies are generally low and random compared to industrial machinery that vibrates at much higher frequencies. One of the most promising and popular strategies to overcome this is frequency up-conversion. The transducing element is actuated at its optimal frequency of operation, higher than the source excitation frequency, through some kind of catch and release mechanism. This is beneficial for efficient power generation. Such devices have now been investigated for a few years and this paper takes a previously introduced piezoelectric rotational harvester, relying on beam plucking for the energy conversion, to the next step by testing the device during a half marathon race. The prototype and data acquisition system are described in detail and the experimental results presented. A comparison of the input excitation, based on an accelerometer readout, and the output voltage of the piezoelectric beam, recorded at the same time, confirm the successful implementation of the system. For a device functional volume of 1.85 cm3, a maximum power output of 7 μW was achieved when the system was worn on the upper arm. However, degradation of the piezoelectric material meant that the performance dropped rapidly from this initial level; this requires further research. Furthermore, the need for intermediate energy storage solutions is discussed, as human motion harvesters only generate power as long as the wearer is actually moving.

The efficiency of photovoltaic cells exposed to pulsed laser light

NASA Technical Reports Server (NTRS)

Lowe, R. A.; Landis, G. A.; Jenkins, P.

1993-01-01

Future space missions may use laser power beaming systems with a free electron laser (FEL) to transmit light to a photovoltaic array receiver. To investigate the efficiency of solar cells with pulsed laser light, several types of GaAs, Si, CuInSe2, and GaSb cells were tested with the simulated pulse format of the induction and radio frequency (RF) FEL. The induction pulse format was simulated with an 800-watt average power copper vapor laser and the RF format with a frequency-doubled mode-locked Nd:YAG laser. Averaged current vs bias voltage measurements for each cell were taken at various optical power levels and the efficiency measured at the maximum power point. Experimental results show that the conversion efficiency for the cells tested is highly dependent on cell minority carrier lifetime, the width and frequency of the pulses, load impedance, and the average incident power. Three main effects were found to decrease the efficiency of solar cells exposed to simulated FEL illumination: cell series resistance, LC 'ringing', and output inductance. Improvements in efficiency were achieved by modifying the frequency response of the cell to match the spectral energy content of the laser pulse with external passive components.

Catalystlike effect of orbital angular momentum on the conversion of transverse to three-dimensional spin states within tightly focused radially polarized beams

NASA Astrophysics Data System (ADS)

Han, Lei; Liu, Sheng; Li, Peng; Zhang, Yi; Cheng, Huachao; Zhao, Jianlin

2018-05-01

We report on the catalystlike effect of orbital angular momentum (OAM) on local spin-state conversion within the tightly focused radially polarized beams associated with optical spin-orbit interaction. It is theoretically demonstrated that the incident OAM can lead to a conversion of purely transverse spin state to a three-dimensional spin state on the focal plane. This conversion can be conveniently manipulated by altering the sign and value of the OAM. By comparing the total OAM and spin angular momentum (SAM) on the incident plane to those on the focal plane, it is indicated that the incident OAM have no participation in the angular momentum intertransfer, and just play a role as a catalyst of local SAM conversion. Such an effect of OAM sheds new light on the optical spin-orbit interaction in tight-focusing processes. The resultant three-dimensional spin states may provide more degrees of freedom in optical manipulation and spin-dependent directive coupling.

Single-crystal phosphors for high-brightness white LEDs/LDs

NASA Astrophysics Data System (ADS)

Víllora, Encarnación G.; Arjoca, Stelian; Inomata, Daisuke; Shimamura, Kiyoshi

2016-03-01

White light-emitting diodes (wLEDs) are the new environmental friendly sources for general lighting purposes. For applications requiring a high-brightness, current wLEDs present overheating problems, which drastically decrease their emission efficiency, color quality and lifetime. This work gives an overview of the recent investigations on single-crystal phosphors (SCPs), which are proposed as novel alternative to conventional ceramic powder phosphors (CPPs). This totally new approach takes advantage of the superior properties of single-crystals in comparison with ceramic materials. SCPs exhibit an outstanding conversion efficiency and thermal stability up to 300°C. Furthermore, compared with encapsulated CPPs, SCPs possess a superior thermal conductivity, so that generated heat can be released efficiently. The conjunction of all these characteristics results in a low temperature rise of SCPs even under high blue irradiances, where conventional CPPs are overheated or even burned. Therefore, SCPs represent the ideal, long-demanded all-inorganic phosphors for high-brightness white light sources, especially those involving the use of high-density laser-diode beams.

The modified scheme of optimized in simulations Cherenkov type high-power microwave oscillator without guiding magnetic field

NASA Astrophysics Data System (ADS)

Guo, Li M.; Shu, T.; Li, Zhi Q.; Ju, Jin C.

2017-12-01

The compactness and miniaturization of high-power-microwave (HPM) systems are drawing more and more attention. Based on this demand, HPM generators without a guiding magnetic field are being developed. This paper presents an X-band Cherenkov type HPM oscillator without the guiding magnetic field. By particle-in-cell codes, this oscillator achieves an efficiency of 40% in simulation. When the diode voltage and current are 620 kV and 9.0 kA, respectively, a TEM mode microwave is generated with a power of 2.2 GW and a frequency of 9.1 GHz. In this oscillator, electrons are modulated in both longitudinal and radial directions, and the radial modulation has a significant effect on the energy conversion efficiency. As analyzed in this paper, the different radial modulation effects depend on the phase matching differences of the microwave and electrons. The modified scheme of simulations achieves a structure with an efficient longitudinal beam-wave interaction and optimized radial modulation.

Helicon thruster plasma modeling: Two-dimensional fluid-dynamics and propulsive performances

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

Ahedo, Eduardo; Navarro-Cavalle, Jaume

2013-04-15

An axisymmetric macroscopic model of the magnetized plasma flow inside the helicon thruster chamber is derived, assuming that the power absorbed from the helicon antenna emission is known. Ionization, confinement, subsonic flows, and production efficiency are discussed in terms of design and operation parameters. Analytical solutions and simple scaling laws for ideal plasma conditions are obtained. The chamber model is then matched with a model of the external magnetic nozzle in order to characterize the whole plasma flow and assess thruster performances. Thermal, electric, and magnetic contributions to thrust are evaluated. The energy balance provides the power conversion between ionsmore » and electrons in chamber and nozzle, and the power distribution among beam power, ionization losses, and wall losses. Thruster efficiency is assessed, and the main causes of inefficiency are identified. The thermodynamic behavior of the collisionless electron population in the nozzle is acknowledged to be poorly known and crucial for a complete plasma expansion and good thrust efficiency.« less

Electro-optic voltage sensor with beam splitting

DOEpatents

Woods, Gregory K.; Renak, Todd W.; Davidson, James R.; Crawford, Thomas M.

2002-01-01

The invention is a miniature electro-optic voltage sensor system capable of accurate operation at high voltages without use of the dedicated voltage dividing hardware typically found in the prior art. The invention achieves voltage measurement without significant error contributions from neighboring conductors or environmental perturbations. The invention employs a transmitter, a sensor, a detector, and a signal processor. The transmitter produces a beam of electromagnetic radiation which is routed into the sensor. Within the sensor the beam undergoes the Pockels electro-optic effect. The electro-optic effect produces a modulation of the beam's polarization, which is in turn converted to a pair of independent conversely-amplitude-modulated signals, from which the voltage of the E-field is determined by the signal processor. The use of converse AM signals enables the signal processor to better distinguish signal from noise. The sensor converts the beam by splitting the beam in accordance with the axes of the beam's polarization state (an ellipse) into at least two AM signals. These AM signals are fed into a signal processor and processed to determine the voltage between a ground conductor and the conductor on which voltage is being measured.

Overview study of Space Power Technologies for the advanced energetics program. [spacecraft

NASA Technical Reports Server (NTRS)

Taussig, R.; Gross, S.; Millner, A.; Neugebauer, M.; Phillips, W.; Powell, J.; Schmidt, E.; Wolf, M.; Woodcock, G.

1981-01-01

Space power technologies are reviewed to determine the state-of-the-art and to identify advanced or novel concepts which promise large increases in performance. The potential for incresed performance is judged relative to benchmarks based on technologies which have been flight tested. Space power technology concepts selected for their potentially high performance are prioritized in a list of R & D topical recommendations for the NASA program on Advanced Energetics. The technology categories studied are solar collection, nuclear power sources, energy conversion, energy storage, power transmission, and power processing. The emphasis is on electric power generation in space for satellite on board electric power, for electric propulsion, or for beamed power to spacecraft. Generic mission categories such as low Earth orbit missions and geosynchronous orbit missions are used to distinguish general requirements placed on the performance of power conversion technology. Each space power technology is judged on its own merits without reference to specific missions or power systems. Recommendations include 31 space power concepts which span the entire collection of technology categories studied and represent the critical technologies needed for higher power, lighter weight, more efficient power conversion in space.

Realization of a mW-level 10.7-eV (λ = 115.6 nm) laser by cascaded third harmonic generation of a Yb:fiber CPA laser at 1-MHz.

PubMed

Zhao, Zhigang; Kobayashi, Yohei

2017-06-12

We demonstrate a 10.7-eV (λ = 115.6 nm) laser with mW levels of average power and a 1-MHz repetition rate, which was driven by the third harmonic radiation (THG), at 347 nm, of an Yb:fiber chirped pulse amplifier (CPA) laser. The 347 nm ultraviolet radiation was obtained by frequency conversion of the high power output of a 1-MHz Yb:fiber CPA, using beta barium borate (BBO) nonlinear crystals. The frequency converted output was focused down into a gas cell filled with a mixture of Ar and Xe, and was subjected to a second THG frequency conversion. The generated 10.7-eV laser was separated from the fundamental beam using a LiF prism and no further separation from other harmonic waves was required. The highest measured output power was ~80 μW, which corresponded to an average power of ~1.25 mW inside the gas cell when the transmission coefficients of the LiF optics were taken into account. The corresponding conversion efficiency from 347 nm down to 115.6 nm was ~2.5 × 10 -4 .

Heterodyne efficiency of a coherent free-space optical communication model through atmospheric turbulence.

PubMed

Ren, Yongxiong; Dang, Anhong; Liu, Ling; Guo, Hong

2012-10-20

The heterodyne efficiency of a coherent free-space optical (FSO) communication model under the effects of atmospheric turbulence and misalignment is studied in this paper. To be more general, both the transmitted beam and local oscillator beam are assumed to be partially coherent based on the Gaussian Schell model (GSM). By using the derived analytical form of the cross-spectral function of a GSM beam propagating through atmospheric turbulence, a closed-form expression of heterodyne efficiency is derived, assuming that the propagation directions for the transmitted and local oscillator beams are slightly different. Then the impacts of atmospheric turbulence, configuration of the two beams (namely, beam radius and spatial coherence width), detector radius, and misalignment angle over heterodyne efficiency are examined. Numerical results suggest that the beam radius of the two overlapping beams can be optimized to achieve a maximum heterodyne efficiency according to the turbulence conditions and the detector radius. It is also found that atmospheric turbulence conditions will significantly degrade the efficiency of heterodyne detection, and compared to fully coherent beams, partially coherent beams are less sensitive to the changes in turbulence conditions and more robust against misalignment at the receiver.

A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

DOE PAGES

Rakhman, A.; Hafez, Mohamed A.; Nanda, Sirish K.; ...

2016-03-31

Here, a high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO 3 crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancementmore » of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.0 GeV and 50 μA.« less

Advances in high power linearly polarized fiber laser and its application

NASA Astrophysics Data System (ADS)

Zhou, Pu; Huang, Long; Ma, Pengfei; Xu, Jiangming; Su, Rongtao; Wang, Xiaolin

2017-10-01

Fiber lasers are now attracting more and more research interest due to their advantages in efficiency, beam quality and flexible operation. Up to now, most of the high power fiber lasers have random distributed polarization state. Linearlypolarized (LP) fiber lasers, which could find wide application potential in coherent detection, coherent/spectral beam combining, nonlinear frequency conversion, have been a research focus in recent years. In this paper, we will present a general review on the achievements of various kinds of high power linear-polarized fiber laser and its application. The recent progress in our group, including power scaling by using power amplifier with different mechanism, high power linearly polarized fiber laser with diversified properties, and various applications of high power linear-polarized fiber laser, are summarized. We have achieved 100 Watt level random distributed feedback fiber laser, kilowatt level continuous-wave (CW) all-fiber polarization-maintained fiber amplifier, 600 watt level average power picosecond polarization-maintained fiber amplifier and 300 watt level average power femtosecond polarization-maintained fiber amplifier. In addition, high power linearly polarized fiber lasers have been successfully applied in 5 kilowatt level coherent beam combining, structured light field and ultrasonic generation.

NDCX-II target experiments and simulations

DOE PAGES

Barnard, J. J.; More, R. M.; Terry, M.; ...

2013-06-13

The ion accelerator NDCX-II is undergoing commissioning at Lawrence Berkeley National Laboratory (LBNL). Its principal mission is to explore ion-driven High Energy Density Physics (HEDP) relevant to Inertial Fusion Energy (IFE) especially in the Warm Dense Matter (WDM) regime. We have carried out hydrodynamic simulations of beam-heated targets for parameters expected for the initial configuration of NDCX-II. For metal foils of order one micron thick (thin targets), the beam is predicted to heat the target in a timescale comparable to the hydrodynamic expansion time for experiments that infer material properties from measurements of the resulting rarefaction wave. We have alsomore » carried out hydrodynamic simulations of beam heating of metallic foam targets several tens of microns thick (thick targets) in which the ion range is shorter than the areal density of the material. In this case shock waves will form and we derive simple scaling laws for the efficiency of conversion of ion energy into kinetic energy of fluid flow. Geometries with a tamping layer may also be used to study the merging of a tamper shock with the end-of-range shock. As a result, this process can occur in tamped, direct drive IFE targets.« less

Study on a discal TEM-TE{sub 11} mode converter loaded high-efficiency magnetically insulated transmission line oscillator

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

Zhang, Xiaoping, E-mail: zhangxiaoping@nudt.edu.cn; Yuan, Chengwei; Li, Yangmei

2015-12-15

An integrative high power microwave device is proposed, which consists of a high-efficiency L-band Magnetically Insulated Transmission Line Oscillator (MILO) and a discal TEM–TE{sub 11} mode converter. The MILO with a shrunken load composed of a step-like cathode and a ladder-like beam collector can generate a 1.58 GHz, 5.7 GW microwave with the efficiency of 20.8% at the diode voltage of 560 kV in simulation. The discal converter utilizes a pair of sectorial two-double radial waveguides and a pair of sectorial cross section waveguides to adjust the phase-difference and realizes the mode conversion in a length of less than halfmore » wavelength at 1.58 GHz. In the preliminary experiment, the proposed device generates over 2 GW, 1.575 GHz microwave with the pulse duration of over 50 ns in a 420 kV diode voltage; the corresponding efficiency is 14.9%; the radiation pattern is the ideal TE{sub 11} mode.« less

A Particle-in-Cell Simulation for the Traveling Wave Direct Energy Converter (TWDEC) for Fusion Propulsion

NASA Technical Reports Server (NTRS)

Chap, Andrew; Tarditi, Alfonso G.; Scott, John H.

2013-01-01

A Particle-in-cell simulation model has been developed to study the physics of the Traveling Wave Direct Energy Converter (TWDEC) applied to the conversion of charged fusion products into electricity. In this model the availability of a beam of collimated fusion products is assumed; the simulation is focused on the conversion of the beam kinetic energy into alternating current (AC) electric power. The model is electrostatic, as the electro-dynamics of the relatively slow ions can be treated in the quasistatic approximation. A two-dimensional, axisymmetric (radial-axial coordinates) geometry is considered. Ion beam particles are injected on one end and travel along the axis through ring-shaped electrodes with externally applied time-varying voltages, thus modulating the beam by forming a sinusoidal pattern in the beam density. Further downstream, the modulated beam passes through another set of ring electrodes, now electrically oating. The modulated beam induces a time alternating potential di erence between adjacent electrodes. Power can be drawn from the electrodes by connecting a resistive load. As energy is dissipated in the load, a corresponding drop in beam energy is measured. The simulation encapsulates the TWDEC process by reproducing the time-dependent transfer of energy and the particle deceleration due to the electric eld phase time variations.

Nonstandard neutrino self-interactions in a supernova and fast flavor conversions

NASA Astrophysics Data System (ADS)

Dighe, Amol; Sen, Manibrata

2018-02-01

We study the effects of nonstandard self-interactions (NSSI) of neutrinos streaming out of a core-collapse supernova. We show that with NSSI, the standard linear stability analysis gives rise to linearly as well as exponentially growing solutions. For a two-box spectrum, we demonstrate analytically that flavor-preserving NSSI lead to a suppression of bipolar collective oscillations. In the intersecting four-beam model, we show that flavor-violating NSSI can lead to fast oscillations even when the angle between the neutrino and antineutrino beams is obtuse, which is forbidden in the standard model. This leads to the new possibility of fast oscillations in a two-beam system with opposing neutrino-antineutrino fluxes, even in the absence of any spatial inhomogeneities. Finally, we solve the full nonlinear equations of motion in the four-beam model numerically, and explore the interplay of fast and slow flavor conversions in the long-time behavior, in the presence of NSSI.

Optimization of Neutral Atom Imagers

NASA Technical Reports Server (NTRS)

Shappirio, M.; Coplan, M.; Balsamo, E.; Chornay, D.; Collier, M.; Hughes, P.; Keller, J.; Ogilvie, K.; Williams, E.

2008-01-01

The interactions between plasma structures and neutral atom populations in interplanetary space can be effectively studied with energetic neutral atom imagers. For neutral atoms with energies less than 1 keV, the most efficient detection method that preserves direction and energy information is conversion to negative ions on surfaces. We have examined a variety of surface materials and conversion geometries in order to identify the factors that determine conversion efficiency. For chemically and physically stable surfaces smoothness is of primary importance while properties such as work function have no obvious correlation to conversion efficiency. For the noble metals, tungsten, silicon, and graphite with comparable smoothness, conversion efficiency varies by a factor of two to three. We have also examined the way in which surface conversion efficiency varies with the angle of incidence of the neutral atom and have found that the highest efficiencies are obtained at angles of incidence greater then 80deg. The conversion efficiency of silicon, tungsten and graphite were examined most closely and the energy dependent variation of conversion efficiency measured over a range of incident angles. We have also developed methods for micromachining silicon in order to reduce the volume to surface area over that of a single flat surface and have been able to reduce volume to surface area ratios by up to a factor of 60. With smooth micro-machined surfaces of the optimum geometry, conversion efficiencies can be increased by an order of magnitude over instruments like LENA on the IMAGE spacecraft without increase the instruments mass or volume.

Scalable, efficient ASICS for the square kilometre array: From A/D conversion to central correlation

NASA Astrophysics Data System (ADS)

Schmatz, M. L.; Jongerius, R.; Dittmann, G.; Anghel, A.; Engbersen, T.; van Lunteren, J.; Buchmann, P.

2014-05-01

The Square Kilometre Array (SKA) is a future radio telescope, currently being designed by the worldwide radio-astronomy community. During the first of two construction phases, more than 250,000 antennas will be deployed, clustered in aperture-array stations. The antennas will generate 2.5 Pb/s of data, which needs to be processed in real time. For the processing stages from A/D conversion to central correlation, we propose an ASIC solution using only three chip architectures. The architecture is scalable - additional chips support additional antennas or beams - and versatile - it can relocate its receiver band within a range of a few MHz up to 4GHz. This flexibility makes it applicable to both SKA phases 1 and 2. The proposed chips implement an antenna and station processor for 289 antennas with a power consumption on the order of 600W and a correlator, including corner turn, for 911 stations on the order of 90 kW.

Surface-State-Dominated Spin-Charge Current Conversion in Topological-Insulator-Ferromagnetic-Insulator Heterostructures.

PubMed

Wang, Hailong; Kally, James; Lee, Joon Sue; Liu, Tao; Chang, Houchen; Hickey, Danielle Reifsnyder; Mkhoyan, K Andre; Wu, Mingzhong; Richardella, Anthony; Samarth, Nitin

2016-08-12

We report the observation of ferromagnetic resonance-driven spin pumping signals at room temperature in three-dimensional topological insulator thin films-Bi_{2}Se_{3} and (Bi,Sb)_{2}Te_{3}-deposited by molecular beam epitaxy on Y_{3}Fe_{5}O_{12} thin films. By systematically varying the Bi_{2}Se_{3} film thickness, we show that the spin-charge conversion efficiency, characterized by the inverse Rashba-Edelstein effect length (λ_{IREE}), increases dramatically as the film thickness is increased from two quintuple layers, saturating above six quintuple layers. This suggests a dominant role of surface states in spin and charge interconversion in topological-insulator-ferromagnet heterostructures. Our conclusion is further corroborated by studying a series of Y_{3}Fe_{5}O_{12}/(Bi,Sb)_{2}Te_{3} heterostructures. Finally, we use the ferromagnetic resonance linewidth broadening and the inverse Rashba-Edelstein signals to determine the effective interfacial spin mixing conductance and λ_{IREE}.

Thermoelectric Properties of Complex Oxide Heterostructures

NASA Astrophysics Data System (ADS)

Cain, Tyler Andrew

Thermoelectrics are a promising energy conversion technology for power generation and cooling systems. The thermal and electrical properties of the materials at the heart of thermoelectric devices dictate conversion efficiency and technological viability. Studying the fundamental properties of potentially new thermoelectric materials is of great importance for improving device performance and understanding the electronic structure of materials systems. In this dissertation, investigations on the thermoelectric properties of a prototypical complex oxide, SrTiO3, are discussed. Hybrid molecular beam epitaxy (MBE) is used to synthesize La-doped SrTiO3 thin films, which exhibit high electron mobilities and large Seebeck coefficients resulting in large thermoelectric power factors at low temperatures. Large interfacial electron densities have been observed in SrTiO3/RTiO 3 (R=Gd,Sm) heterostructures. The thermoelectric properties of such heterostructures are investigated, including the use of a modulation doping approach to control interfacial electron densities. Low-temperature Seebeck coefficients of extreme electron-density SrTiO3 quantum wells are shown to provide insight into their electronic structure.

Effect of Ion Escape Velocity and Conversion Surface Material on H- Production

NASA Astrophysics Data System (ADS)

Tarvainen, O.; Kalvas, T.; Komppula, J.; Koivisto, H.; Geros, E.; Stelzer, J.; Rouleau, G.; Johnson, K. F.; Carmichael, J.

2011-09-01

According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H- production. A converter-type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was affected by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H- no direct gain of extracted beam current can be achieved by increasing the converter voltage. The conversion efficiency of H- was observed to vary with converter voltage and follow the existing theories in qualitative manner. We present calculations predicting relative H- yields from different cesiated surfaces with comparison to experimental observations from different types of H- ion sources. Utilizing materials exhibiting negative electron affinity and exposed to UV-light is considered for Cesium-free H-/D- production.

5 MV 30 mA industrial electron processing system

NASA Astrophysics Data System (ADS)

Hoshi, Y.; Mizusawa, K.

1991-05-01

Industrial electron beam processing systems have been in use in various application fields such as: improving heat resistivity of wire insulation; controlling quality of automobile rubber tires and melt index characteristics of PE foams; and curing paintings or printing inks. Recently, there has come up a need for electron beam with an energy higher than 3 MV in order to disinfect salmonella in chicken meat, to kill bugs in fruits, and to sterilize medical disposables. To meet this need we developed a 5 MV 30 mA electron processing system with an X-ray conversion target. The machine was tested in NHV's plant in Kyoto at continuous operation of full voltage and full current. It proved to be very steady in operation with a high efficiency (as much as 72%). Also, the X-ray target was tested in a continuous run of 5 MV 30 mA (150 kW). It proved to be viable in industrial utilization. This paper introduces the process and the results of the development.

Giant collimated gamma-ray flashes

NASA Astrophysics Data System (ADS)

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

2018-06-01

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

An overview of Laser-Produced Relativistic Positrons in the Laboratory

NASA Astrophysics Data System (ADS)

Edghill, Brandon; Williams, Gerald; Chen, Hui; Beg, Farhat

2017-10-01

The production of relativistic positrons using ultraintense lasers can facilitate studies of fundamental pair plasma science in the relativistic regime and laboratory studies of scaled energetic astrophysical mechanisms such as gamma ray bursts. The positron densities and spatial scales required for these applications, however, are larger than current capabilities. Here, we present an overview of the experimental laser-produced positron results and their respective modeling for both the direct laser-irradiated process and the indirect process (laser wakefield accelerated electrons irradiating a high-Z converter). Conversion efficiency into positrons and positron beam characteristics are compared, including total pair yield, mean energy, angular divergence, and inferred pair density for various laser and target conditions. Prospects towards increasing positron densities and beam repetition rates will also be discussed. 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 LDRD (#17-ERD-010).

Improved Biomolecular Thin-Film Sensor based on Plasmon Waveguide Resonance

NASA Astrophysics Data System (ADS)

Byard, Courtney; Aslan, Mustafa; Mendes, Sergio

2009-05-01

The design, fabrication, and characterization of a plasmon waveguide resonance (PWR) sensor are presented. Glass substrates are coated with a 35 nm gold film using electron beam evaporation, and then covered with a 143 nm aluminum oxide waveguide using an atomic layer deposition process, creating a smooth, highly transparent dielectric film. When probed in the Kretschmann configuration, the structure allows for an efficient conversion of an incident optical beam into a surface wave, which is mainly confined in the dielectric layer and exhibits a deep and narrow angular resonance. The performance (reflectance vs. incidence angle in TE polarization) is modeled using a transfer-matrix approach implemented into a Mathematica code. Our simulations and experimental data are compared with that of surface plasmon resonance (SPR) sensor using the same criteria. We show that the resolution of PWR is approximately ten times better than SPR, opening opportunities for more sensitive studies in various applications including research in protein interactions, pharmaceutical drug development, and food analysis.

Searching for O-X-B mode-conversion window with monitoring of stray microwave radiation in LHD

NASA Astrophysics Data System (ADS)

Igami, H.; Kubo, S.; Laqua, H. P.; Nagasaki, K.; Inagaki, S.; Notake, T.; Shimozuma, T.; Yoshimura, Y.; Mutoh, T.; LHD Experimental Group

2006-10-01

In the Large Helical Device, the stray microwave radiation is monitored by using so-called sniffer probes during electron cyclotron heating. In monitoring the stray radiation, we changed the microwave beam injection angle and search the O-X-B mode-conversion window to excite electron Bernstein waves (EBWs). When the microwave beam is injected toward the vicinity of the predicted O-X-B mode-conversion window, the electron temperature rises in the central part of overdense plasmas. In that case, the stray radiation level near the injection antenna becomes low. These results indicate that monitoring the stray radiation near the injection antenna is helpful in confirming the effectiveness of excitation of EBWs simply without precise analysis.

Broad beam ion implanter

DOEpatents

Leung, K.N.

1996-10-08

An ion implantation device for creating a large diameter, homogeneous, ion beam is described, as well as a method for creating same, wherein the device is characterized by extraction of a diverging ion beam and its conversion by ion beam optics to an essentially parallel ion beam. The device comprises a plasma or ion source, an anode and exit aperture, an extraction electrode, a divergence-limiting electrode and an acceleration electrode, as well as the means for connecting a voltage supply to the electrodes. 6 figs.

Broad beam ion implanter

DOEpatents

Leung, Ka-Ngo

1996-01-01

An ion implantation device for creating a large diameter, homogeneous, ion beam is described, as well as a method for creating same, wherein the device is characterized by extraction of a diverging ion beam and its conversion by ion beam optics to an essentially parallel ion beam. The device comprises a plasma or ion source, an anode and exit aperture, an extraction electrode, a divergence-limiting electrode and an acceleration electrode, as well as the means for connecting a voltage supply to the electrodes.

Electroviscous effect and electrokinetic energy conversion in time periodic pressure-driven flow through a parallel-plate nanochannel with surface charge-dependent slip

NASA Astrophysics Data System (ADS)

Buren, Mandula; Jian, Yongjun; Zhao, Yingchun; Chang, Long

2018-05-01

In this paper we analytically investigate the electroviscous effect and electrokinetic energy conversion in the time periodic pressure-driven flow of an incompressible viscous Newtonian liquid through a parallel-plate nanochannel with surface charge-dependent slip. Analytical and semi-analytical solutions for electric potential, velocity and streaming electric field are obtained and are utilized to compute electrokinetic energy conversion efficiency. The results show that velocity amplitude and energy conversion efficiency are reduced when the effect of surface charge on slip length is considered. The surface charge effect increases with zeta potential and ionic concentration. In addition, the energy conversion efficiency is large when the ratio of channel half-height to the electric double layer thickness is small. The boundary slip results in a large increase in energy conversion. Higher values of the frequency of pressure pulsation lead to higher values of the energy conversion efficiency. We also obtain the energy conversion efficiency in constant pressure-driven flow and find that the energy conversion efficiency in periodical pressure-driven flow becomes larger than that in constant pressure-driven flow when the frequency is large enough.

Method to monitor HC-SCR catalyst NOx reduction performance for lean exhaust applications

DOEpatents

Viola, Michael B [Macomb Township, MI; Schmieg, Steven J [Troy, MI; Sloane, Thompson M [Oxford, MI; Hilden, David L [Shelby Township, MI; Mulawa, Patricia A [Clinton Township, MI; Lee, Jong H [Rochester Hills, MI; Cheng, Shi-Wai S [Troy, MI

2012-05-29

A method for initiating a regeneration mode in selective catalytic reduction device utilizing hydrocarbons as a reductant includes monitoring a temperature within the aftertreatment system, monitoring a fuel dosing rate to the selective catalytic reduction device, monitoring an initial conversion efficiency, selecting a determined equation to estimate changes in a conversion efficiency of the selective catalytic reduction device based upon the monitored temperature and the monitored fuel dosing rate, estimating changes in the conversion efficiency based upon the determined equation and the initial conversion efficiency, and initiating a regeneration mode for the selective catalytic reduction device based upon the estimated changes in conversion efficiency.

Effects of Light and Electron Beam Irradiation on Halide Perovskites and Their Solar Cells.

PubMed

Klein-Kedem, Nir; Cahen, David; Hodes, Gary

2016-02-16

Hybrid alkylammonium lead halide perovskite solar cells have, in a very few years of research, exceeded a light-to-electricity conversion efficiency of 20%, not far behind crystalline silicon cells. These perovskites do not contain any rare element, the amount of toxic lead used is very small, and the cells can be made with a low energy input. They therefore already conform to two of the three requirements for viable, commercial solar cells-efficient and cheap. The potential deal-breaker is their long-term stability. While reasonable short-term (hours) and even medium term (months) stability has been demonstrated, there is concern whether they will be stable for the two decades or more expected from commercial cells in view of the intrinsically unstable nature of these materials. In particular, they have a tendency to be sensitive to various types of irradiation, including sunlight, under certain conditions. This Account focuses on the effect of irradiation on the hybrid (and to a small degree, all-inorganic) lead halide perovskites and their solar cells. It is split up into two main sections. First, we look at the effect of electron beams on the materials. This is important, since such beams are used for characterization of both the perovskites themselves and cells made from them (electron microscopy for morphological and compositional characterization; electron beam-induced current to study cell operation mechanism; cathodoluminescence for charge carrier recombination studies). Since the perovskites are sensitive to electron beam irradiation, it is important to minimize beam damage to draw valid conclusions from such measurements. The second section treats the effect of visible and solar UV irradiation on the perovskites and their cells. As we show, there are many such effects. However, those affecting the perovskite directly need not necessarily always be detrimental to the cells, while those affecting the solar cells, which are composed of several other phases as well as the perovskite light absorber, are not always due to the perovskite itself. While we cannot yet say whether perovskite solar cells will or will not be stable over the long-term, the information in this Account should be a useful source to help achieve this goal.

Artificial perfect electric conductor-perfect magnetic conductor anisotropic metasurface for generating orbital angular momentum of microwave with nearly perfect conversion efficiency

NASA Astrophysics Data System (ADS)

Chen, Menglin L. N.; Jiang, Li Jun; Sha, Wei E. I.

2016-02-01

Orbital angular momentum (OAM) is a promising degree of freedom for fundamental studies in electromagnetics and quantum mechanics. The unlimited state space of OAM shows a great potential to enhance channel capacities of classical and quantum communications. By exploring the Pancharatnam-Berry phase concept and engineering anisotropic scatterers in a metasurface with spatially varying orientations, a plane wave with zero OAM can be converted to a vortex beam carrying nonzero OAM. In this paper, we proposed two types of novel perfect electric conductor-perfect magnetic conductor anisotropic metasurfaces. One is composed of azimuthally continuous loops and the other is constructed by azimuthally discontinuous dipole scatterers. Both types of metasurfaces are mounted on a mushroom-type high impedance surface. Compared to previous metasurface designs for generating OAM, the proposed ones achieve nearly perfect conversion efficiency. In view of the eliminated vertical component of electric field, the continuous metasurface shows very smooth phase pattern at the near-field region, which cannot be achieved by convectional metasurfaces composed of discrete scatterers. On the other hand, the metasurface with discrete dipole scatterers shows a great flexibility to generate OAM with arbitrary topological charges. Our work is fundamentally and practically important to high-performance OAM generation.

Completely monolithic linearly polarized high-power fiber laser oscillator

NASA Astrophysics Data System (ADS)

Belke, Steffen; Becker, Frank; Neumann, Benjamin; Ruppik, Stefan; Hefter, Ulrich

2014-03-01

We have demonstrated a linearly polarized cw all-in-fiber oscillator providing 1 kW of output power and a polarization extinction ratio (PER) of up to 21.7 dB. The design of the laser oscillator is simple and consists of an Ytterbium-doped polarization maintaining large mode area (PLMA) fiber and suitable fiber Bragg gratings (FBG) in matching PLMA fibers. The oscillator has nearly diffraction-limited beam quality (M² < 1.2). Pump power is delivered via a high power 6+1:1 pump coupler. The slope efficiency of the laser is 75 %. The electro/optical efficiency of the complete laser system is ~30 % and hence in the range of Rofin's cw non-polarized fiber lasers. Choosing an adequate bending diameter for the Yb-doped PLMA fiber, one polarization mode as well as higher order modes are sufficiently supressed1. Resulting in a compact and robust linearly polarized high power single mode laser without external polarizing components. Linearly polarized lasers are well established for one dimensional cutting or welding applications. Using beam shaping optics radially polarized laser light can be generated to be independent from the angle of incident to the processing surface. Furthermore, high power linearly polarized laser light is fundamental for nonlinear frequency conversion of nonlinear materials.

Study on the near-field non-linearity (SMILE) of high power diode laser arrays

NASA Astrophysics Data System (ADS)

Zhang, Hongyou; Jia, Yangtao; Li, Changxuan; Zah, Chung-en; Liu, Xingsheng

2018-02-01

High power laser diodes have been found a wide range of industrial, space, medical applications, characterized by high conversion efficiency, small size, light weight and a long lifetime. However, due to thermal induced stress, each emitter in a semiconductor laser bar or array is displaced along p-n junction, resulting of each emitter is not in a line, called Near-field Non-linearity. Near-field Non-linearity along laser bar (also known as "SMILE") determines the outcome of optical coupling and beam shaping [1]. The SMILE of a laser array is the main obstacle to obtain good optical coupling efficiency and beam shaping from a laser array. Larger SMILE value causes a larger divergence angle and a wider line after collimation and focusing, respectively. In this letter, we simulate two different package structures based on MCC (Micro Channel Cooler) with Indium and AuSn solders, including the distribution of normal stress and the SMILE value. According to the theoretical results, we found the distribution of normal stress on laser bar shows the largest in the middle and drops rapidly near both ends. At last, we did another experiment to prove that the SMILE value of a laser bar was mainly affected by the die bonding process, rather than the operating condition.

Single crystal CVD diamond membranes for betavoltaic cells

NASA Astrophysics Data System (ADS)

Delfaure, C.; Pomorski, M.; de Sanoit, J.; Bergonzo, P.; Saada, S.

2016-06-01

A single crystal diamond large area thin membrane was assembled as a p-doped/Intrinsic/Metal (PIM) structure and used in a betavoltaic configuration. When tested with a 20 keV electron beam from a high resolution scanning electron microscope, we measured an open circuit voltage (Voc) of 1.85 V, a charge collection efficiency (CCE) of 98%, a fill-factor of 80%, and a total conversion efficiency of 9.4%. These parameters are inherently linked to the diamond membrane PIM structure that allows full device depletion even at 0 V and are among the highest reported up to now for any other material tested for betavoltaic devices. It enables to drive a high short-circuit current Isc up to 7.12 μA, to reach a maximum power Pmax of 10.48 μW, a remarkable value demonstrating the high-benefit of diamond for the realization of long-life radioisotope based micro-batteries.

DKDP crystal growth controlled by cooling rate

NASA Astrophysics Data System (ADS)

Xie, Xiaoyi; Qi, Hongji; Shao, Jianda

2017-08-01

The performance of deuterated potassium dihydrogen phosphate (DKDP) crystal directly affects beam quality, energy and conversion efficiency in the Inertial Confinement Fusion（ICF）facility, which is related with the initial saturation temperature of solution and the real-time supersaturation during the crystal growth. However, traditional method to measure the saturation temperature is neither efficient nor accurate enough. Besides, the supersaturation is often controlled by experience, which yields the higher error and leads to the instability during the crystal growth. In this paper, DKDP solution with 78% deuteration concentration is crystallized in different temperatures. We study the relation between solubility and temperature of DKDP and fit a theoretical curve with a parabola model. With the model, the measurement of saturation temperature is simplified and the control precision of the cooling rate is improved during the crystal growth, which is beneficial for optimizing the crystal growth process.

Beyond Extreme Ultra Violet (BEUV) Radiation from Spherically symmetrical High-Z plasmas

NASA Astrophysics Data System (ADS)

Yoshida, Kensuke; Fujioka, Shinsuke; Higashiguchi, Takeshi; Ugomori, Teruyuki; Tanaka, Nozomi; Kawasaki, Masato; Suzuki, Yuhei; Suzuki, Chihiro; Tomita, Kentaro; Hirose, Ryouichi; Eshima, Takeo; Ohashi, Hayato; Nishikino, Masaharu; Scally, Enda; Nshimura, Hiroaki; Azechi, Hiroshi; O'Sullivan, Gerard

2016-03-01

Photo-lithography is a key technology for volume manufacture of high performance and compact semiconductor devices. Smaller and more complex structures can be fabricated by using shorter wavelength light in the photolithography. One of the most critical issues in development of the next generation photo-lithography is to increase energy conversion efficiency (CE) from laser to shorter wavelength light. Experimental database of beyond extreme ultraviolet (BEUV) radiation was obtained by using spherically symmetrical high-Z plasmas generated with spherically allocated laser beams. Absolute energy and spectra of BEUV light emitted from Tb, Gd, and Mo plasmas were measured with a absolutely calibrated BEUV calorimeter and a transmission grating spectrometer. 1.0 x 1012 W/cm2 is the optimal laser intensity to produced efficient BEUV light source plasmas with Tb and Gd targets. Maximum CE is achieved at 0.8% that is two times higher than the published CEs obtained with planar targets.

Compact 151 W green laser with U-type resonator for prostate surgery

NASA Astrophysics Data System (ADS)

Bazyar, Hossein; Aghaie, Mohammad; Daemi, Mohammad Hossein; Bagherzadeh, Seyed Morteza

2013-04-01

We analyzed, designed and fabricated a U-type resonator for intra-cavity frequency doubling of a diode-side-pumped Q-switched Nd:YAG rod laser with high power and high stability for surgery of prostatic tissue. The resonator stability conditions were analyzed graphically in the various configurations for a U-type resonator. We obtained green light at 532 nm using a single KTP crystal, with average output power of 151 W at 10 kHz repetition rate, and with 113 ns pulse duration at 810 W input pump power. We achieved 1064-532 nm conversion efficiency of 75.8%, and pump-to-green optical-optical efficiency of 18.6%. The green power fluctuation was ±1.0% and pointing stability was better than 4 μrad. The green laser output was coupled to a side-firing medical fiber to transfer the laser beam to the prostatic tissue.

Probing Photocurrent Nonuniformities in the Subcells of Monolithic Perovskite/Silicon Tandem Solar Cells.

PubMed

Song, Zhaoning; Werner, Jérémie; Shrestha, Niraj; Sahli, Florent; De Wolf, Stefaan; Niesen, Björn; Watthage, Suneth C; Phillips, Adam B; Ballif, Christophe; Ellingson, Randy J; Heben, Michael J

2016-12-15

Perovskite/silicon tandem solar cells with high power conversion efficiencies have the potential to become a commercially viable photovoltaic option in the near future. However, device design and optimization is challenging because conventional characterization methods do not give clear feedback on the localized chemical and physical factors that limit performance within individual subcells, especially when stability and degradation is a concern. In this study, we use light beam induced current (LBIC) to probe photocurrent collection nonuniformities in the individual subcells of perovskite/silicon tandems. The choices of lasers and light biasing conditions allow efficiency-limiting effects relating to processing defects, optical interference within the individual cells, and the evolution of water-induced device degradation to be spatially resolved. The results reveal several types of microscopic defects and demonstrate that eliminating these and managing the optical properties within the multilayer structures will be important for future optimization of perovskite/silicon tandem solar cells.

WISPER: Wirless Space Power Experiment

NASA Technical Reports Server (NTRS)

Hawkins, Joseph

1993-01-01

The 1993 Advanced Design Project at the University of Alaska Fairbanks was to design a spacecraft as a technology demonstration of wireless power transmission (WPT). With cost effectiveness as a design constraint, a micro-satellite in low earth orbit (LEO) was chosen for the mission. Existing and near term technologies were analyzed and selected for the project. In addition to the conceptual design of the payload, support systems, and structure, the analysis included attention to safety, environmental impact, cost, and schedule for construction and operation. Wireless power beaming is not a new concept. Experimental demonstrations and study efforts have continued since the early 1960's. With the latest progress in transmitter and receiver technology, the next natural step is to beam power from earth to space. This proposed flight demonstration will advance the science of power beaming and prove the viability of various applications of WPT in space. Two methods of power beaming will be examined during the two separate phases of the spacecraft life. The first phase will demonstrate the technology and examine the theory of microwave power transmission at a high frequency. Special aspects of the first phase will include a highly accurate attitude control system and a 14 m inflatable parabolic antenna. The second phase will investigate the utilization of high intensity laser power using modified photovoltaic arrays. Special instrumentation on the spacecraft will measure the conversion efficiency from the received microwave or laser power to direct current power.

Numerical analysis of amplification of picosecond pulses in a THL-100 laser system with an increase in the pump energy of the XeF(C – A) amplifier

NASA Astrophysics Data System (ADS)

Yastremskii, A. G.; Ivanov, N. G.; Losev, V. F.

2018-03-01

Energy characteristics of laser radiation with a pulse width of 50 ps at an elevated pump energy of the XeF(C – A) amplifier of a hybrid THL-100 laser system are analysed numerically. The dynamics of the change in the energy and maximum intensity of laser radiation with an increase in the pump energy of the XeF(C – A) amplifier from 270 to 400 J is investigated. The results of studying the influence of the input beam divergence on the energy characteristics of the output beam are presented. It is shown that, for the existing system of mirrors, an increase in the pump energy to 400 J leads to an increase in the output energy from 3.2 to 5.5 J at a maximum radiation intensity of 57 GW cm-2. A system of amplifier mirrors with 27 laser beam passes and enlarged divergence angle of the amplified beam is considered. Theoretically, the proposed system of mirrors allows one to increase the laser pulse energy to 7.5 J at a maximum intensity of no more than 14.8 GW cm-2. The calculated efficiency of the conversion of the pump energy absorbed in the amplifier gas chamber into the lasing energy exceeds 3% in this regime.

Development of solar concentrators for high-power solar-pumped lasers.

PubMed

Dinh, T H; Ohkubo, T; Yabe, T

2014-04-20

We have developed unique solar concentrators for solar-pumped solid-state lasers to improve both efficiency and laser output power. Natural sunlight is collected by a primary concentrator which is a 2  m×2  m Fresnel lens, and confined by a cone-shaped hybrid concentrator. Such solar power is coupled to a laser rod by a cylinder with coolant surrounding it that is called a liquid light-guide lens (LLGL). Performance of the cylindrical LLGL has been characterized analytically and experimentally. Since a 14 mm diameter LLGL generates efficient and uniform pumping along a Nd:YAG rod that is 6 mm in diameter and 100 mm in length, 120 W cw laser output is achieved with beam quality factor M2 of 137 and overall slope efficiency of 4.3%. The collection efficiency is 30.0  W/m2, which is 1.5 times larger than the previous record. The overall conversion efficiency is more than 3.2%, which can be comparable to a commercial lamp-pumped solid-state laser. The concept of the light-guide lens can be applied for concentrator photovoltaics or other solar energy optics.

Determination of multislice computed tomography dose index (CTDI) using optically stimulated luminescence technology.

PubMed

Ruan, Chun; Yukihara, Eduardo G; Clouse, William J; Gasparian, Patricia B R; Ahmad, Salahuddin

2010-07-01

The extensive use of multislice computed tomography (MSCT) and the associated increase in patient dose calls for an accurate dose evaluation technique. Optically stimulated luminescence (OSL) dosimetry provides a potential solution to the arising concerns over patient dose. This study was intended to evaluate the feasibility and accuracy of OSL dosimeter systems in the diagnostic CT x-ray beam energy range. MSCT dose profiles were measured by irradiating OSL strips placed inside the extended PMMA head and body phantoms at different scan conditions by varying kVp settings (100, 120, and 140 kVp) and collimated beam widths (5, 10, 20, and 40 mm). All scans in this study were performed using a GE Lightspeed VCT scanner in axial mode. The exposed strips were then read out using a custom-made OSL strip reader and corrected with field-specific conversion factors. Based on the corrected OSL dose profile, the CTDI(450-OSL) and CTDI(l00-OSL) were evaluated. CTDI(100-IC) was also obtained using a 100 mm long pencil ionization chamber for accuracy verification. CTDI(100-efficiency) can be further evaluated by calculating the ratio of CTDI(100-OSL) and CTDI(450-OSL), which was compared to results from previous studies as well. The OSL detectors were found to have good sensitivity and dose response over a wide range of diagnostic CT x-ray beam energy viz. the primary beam and the scatter tail section of the dose profile. The differences between CTDI100 values obtained using the OSL strips and those obtained with 100 mm long pencil ionization chamber were < +/- 5% for all scan conditions, indicating good accuracy of the OSL system. It was also found that the CTDI(100-efficiency) did not significantly change as the beam width increased and tube voltage changed. The average CTDI(100-efficiency) at the center of the head and body phantoms were 72.6% and 56.2%, respectively. The corresponding values for the periphery of the head and body phantoms were 85.0% and 81.7%. These results agreed very well with previous results from the literature using other detection techniques or Monte Carlo simulations. The LED-based OSL system can be an accurate alternative device for CT dose evaluations. CTDI100 measurement with the use of a 100 mm pencil ionization chamber substantially underestimates the CTDIinfinity value even with 5 mm collimated beam width. The established complete set of CTDI(100-efficiency) correction factors for various scan parameters allows for accurately estimating CTDIinfinity with the current use of pencil chamber and dose phantoms. Combined with the simple calibration, it gives this work great potential to be used not only in routine clinical quality assurance checks but also as a promising tool for patient organ dose assessment.

Flat nonlinear optics: metasurfaces for efficient frequency mixing

NASA Astrophysics Data System (ADS)

Nookala, Nishant; Lee, Jongwon; Liu, Yingnan; Bishop, Wells; Tymchenko, Mykhailo; Gomez-Diaz, J. Sebastian; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus-Christian; Wolf, Omri; Brener, Igal; Alu, Andrea; Belkin, Mikhail A.

2017-02-01

Gradient metasurfaces, or ultrathin optical components with engineered transverse impedance gradients along the surface, are able to locally control the phase and amplitude of the scattered fields over subwavelength scales, enabling a broad range of linear components in a flat, integrable platform1-4. On the contrary, due to the weakness of their nonlinear optical responses, conventional nonlinear optical components are inherently bulky, with stringent requirements associated with phase matching and poor control over the phase and amplitude of the generated beam. Nonlinear metasurfaces have been recently proposed to enable frequency conversion in thin films without phase-matching constraints and subwavelength control of the local nonlinear phase5-8. However, the associated optical nonlinearities are far too small to produce significant nonlinear conversion efficiency and compete with conventional nonlinear components for pump intensities below the materials damage threshold. Here, we report multi-quantum-well based gradient nonlinear metasurfaces with second-order nonlinear susceptibility over 106 pm/V for second harmonic generation at a fundamental pump wavelength of 10 μm, 5-6 orders of magnitude larger than traditional crystals. Further, we demonstrate the efficacy of this approach to designing metasurfaces optimized for frequency conversion over a large range of wavelengths, by reporting multi-quantum-well and metasurface structures optimized for a pump wavelength of 6.7 μm. Finally, we demonstrate how the phase of this nonlinearly generated light can be locally controlled well below the diffraction limit using the Pancharatnam-Berry phase approach5,7,9, opening a new paradigm for ultrathin, flat nonlinear optical components.

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

Chakraborty, S.; Izaguirre, I.; Raffelt, G.G.

Neutrino-neutrino refraction in dense media can cause self-induced flavor conversion triggered by collective run-away modes of the interacting flavor oscillators. The growth rates were usually found to be of order a typical vacuum oscillation frequency Δ m{sup 2}/2E. However, even in the simple case of a ν{sub e} beam interacting with an opposite-moving ν-bar {sub e} beam, and allowing for spatial inhomogeneities, the growth rate of the fastest-growing Fourier mode is of order μ=√2 G{sub F} n{sub ν}, a typical ν–ν interaction energy. This growth rate is much larger than the vacuum oscillation frequency and gives rise to flavor conversion on a muchmore » shorter time scale. This phenomenon of 'fast flavor conversion' occurs even for vanishing Δ m{sup 2}/2E and thus does not depend on energy, but only on the angle distributions. Moreover, it does not require neutrinos to mix or to have masses, except perhaps for providing seed disturbances. We also construct a simple homogeneous example consisting of intersecting beams and study a schematic supernova model proposed by Ray Sawyer, where ν{sub e} and ν-bar {sub e} emerge with different zenith-angle distributions, the key ingredient for fast flavor conversion. What happens in realistic astrophysical scenarios remains to be understood.« less

The optimal balance between quality and efficiency in proton radiography imaging technique at various proton beam energies: A Monte Carlo study.

PubMed

Biegun, A K; van Goethem, M-J; van der Graaf, E R; van Beuzekom, M; Koffeman, E N; Nakaji, T; Takatsu, J; Visser, J; Brandenburg, S

2017-09-01

Proton radiography is a novel imaging modality that allows direct measurement of the proton energy loss in various tissues. Currently, due to the conversion of so-called Hounsfield units from X-ray Computed Tomography (CT) into relative proton stopping powers (RPSP), the uncertainties of RPSP are 3-5% or higher, which need to be minimized down to 1% to make the proton treatment plans more accurate. In this work, we simulated a proton radiography system, with position-sensitive detectors (PSDs) and a residual energy detector (RED). The simulations were built using Geant4, a Monte Carlo simulation toolkit. A phantom, consisting of several materials was placed between the PSDs of various Water Equivalent Thicknesses (WET), corresponding to an ideal detector, a gaseous detector, silicon and plastic scintillator detectors. The energy loss radiograph and the scattering angle distributions of the protons were studied for proton beam energies of 150MeV, 190MeV and 230MeV. To improve the image quality deteriorated by the multiple Coulomb scattering (MCS), protons with small angles were selected. Two ways of calculating a scattering angle were considered using the proton's direction and position. A scattering angle cut of 8.7mrad was applied giving an optimal balance between quality and efficiency of the radiographic image. For the three proton beam energies, the number of protons used in image reconstruction with the direction method was half the number of protons kept using the position method. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

High energy 523 nm ND:YLF pulsed slab laser with novel pump beam waveguide design

NASA Astrophysics Data System (ADS)

Yang, Qi; Zhu, Xiaolei; Ma, Jian; Lu, Tingting; Ma, Xiuhua; Chen, Weibiao

2015-11-01

A laser diode pumped Nd:YLF master oscillator power amplifier (MOPA) green laser system with high pulse energy and high stable output is demonstrated. At a repetition rate of 50 Hz, 840 mJ pulse energy, 9.1 ns pulse width of 1047 nm infrared laser emitting is obtained from the MOPA system. The corresponding peak power is 93 MW. Extra-cavity frequency doubling with a LiB3O5 crystal, pulse energy of 520 mJ at 523 nm wavelength is achieved. The frequency conversion efficiency reaches up to 62%. The output pulse energy instability of the laser system is less than 0.6% for one hour.

Design of broadband multilayer dichroic coating for a high-efficiency solar energy harvesting system.

PubMed

Jiachen, Wang; Lee, Sang Bae; Lee, Kwanil

2015-05-20

We report on the design and performance of a broadband dichroic coating for a solar energy conversion system. As a spectral beam splitter, the coating facilitates a hybrid system that combines a photovoltaic cell with a thermal collector. When positioned at a 45° angle with respect to incident light, the coating provides high reflectance in the 40-1100 nm and high transmission in the 1200-2000 nm ranges for a photovoltaic cell and a thermal collector, respectively. Numerical simulations show that our design leads to a sharp transition between the reflection and transmission bands, low ripples in both bands, and slight polarization dependence.

Terahertz generation via laser coupling to anharmonic carbon nanotube array

NASA Astrophysics Data System (ADS)

Sharma, Soni; Vijay, A.

2018-02-01

A scheme of terahertz radiation generation employing a matrix of anharmonic carbon nanotubes (CNTs) embedded in silica is proposed. The matrix is irradiated by two collinear laser beams that induce large excursions on CNT electrons and exert a nonlinear force at the beat frequency ω = ω1-ω2. The force derives a nonlinear current producing THz radiation. The THz field is resonantly enhanced at the plasmon resource, ω = ω p ( 1 + β ) / √{ 2 } , where ωp is the plasma frequency and β is a characteristic parameter. Collisions are a limiting factor, suppressing the plasmon resonance. For typical values of plasma parameters, we obtain power conversion efficiency of the order of 10-6.

High resolution kilometric range optical telemetry in air by radio frequency phase measurement

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

Guillory, Joffray; García-Márquez, Jorge; Truong, Daniel

2016-07-15

We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances upmore » to 1.2 km.« less

KSC-01PP1402

NASA Image and Video Library

2001-07-27

KENNEDY SPACE CENTER, Fla. -- On Launch Pad 39A, two Hitchhiker Experiments Advancing Technology (HEAT) payloads are loaded onto Discovery’s port adapter beam in the payload bay. At left is the Space Experiment Module, an educational initiative to increase educational access to space. The canister contains up to 10 small, enclosed modules that contain separate, passive experiments designed and constructed by students. Many of the experiments will study the growing characteristics of plants subjected to the space environment. At right is the Get Away Special canister containing the Alkali Metal Thermal-to-Electric Converter (AMTEC), designed for efficient conversion of heat into electrical energy. The HEAT payloads are flying on mission STS-105, scheduled to launch Aug. 9, 2001

Tapered enlarged ends in multimode optical fibers.

PubMed

Brenci, M; Falciai, R; Scheggi, A M

1982-01-15

Radiation characteristics of multimode fibers with enlarged tapers were investigated on a number of samples obtained by varying the fiber drawing speed with a given law corresponding to a prefixed taper profile. The characterization of the fibers was made by near- and far-field intensity pattern measurements as well as by measuring the losses introduced by the taper. With a suitable choice of parameters the taper constitutes a reasonable low-loss component useful, for example, for either efficient coupling to large-spot high-power density sources or connecting fibers of different sizes. Conversely at the exit of the fiber the taper can be used for beam shaping which is of interest for mechanical or surgical applications.

Optimisation of X-ray emission from a laser plasma source for the realisation of microbeam in sub-keV region.

PubMed

Di Paolo Emilio, M; Festuccia, R; Palladino, L

2015-09-01

In this work, the X-ray emission generated from a plasma produced by focusing Nd-YAG laser beam on the Mylar and Yttrium targets will be characterised. The goal is to reach the best condition that optimises the X-ray conversion efficiency at 500 eV (pre-edge of the Oxigen K-shell), strongly absorbed by carbon-based structures. The characteristics of the microbeam optical system, the software/hardware control and the preliminary measurements of the X-ray fluence will be presented. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Coupling efficiency of laser beam to multimode fiber

NASA Astrophysics Data System (ADS)

Niu, Jinfu; Xu, Jianqiu

2007-06-01

The coupling efficiency of laser beam to multimode fiber is given by geometrical optics, and the relation between the maximum coupling efficiency and the beam propagation factor M2 is analyzed. An equivalent factor MF2 for the multimode fiber is introduced to characterize the fiber coupling capability. The coupling efficiency of laser beam to multimode fiber is calculated in respect of the ratio M2/MF2 by the overlapping integral theory. The optimal coupling efficiency can be roughly estimated by the ratio of M2 to MF2 but with a large error range. The deviation comes from the lacks of information on the detail of phase and intensity profile in the beam factor M2.

Quantum illumination with Gaussian states.

PubMed

Tan, Si-Hui; Erkmen, Baris I; Giovannetti, Vittorio; Guha, Saikat; Lloyd, Seth; Maccone, Lorenzo; Pirandola, Stefano; Shapiro, Jeffrey H

2008-12-19

An optical transmitter irradiates a target region containing a bright thermal-noise bath in which a low-reflectivity object might be embedded. The light received from this region is used to decide whether the object is present or absent. The performance achieved using a coherent-state transmitter is compared with that of a quantum-illumination transmitter, i.e., one that employs the signal beam obtained from spontaneous parametric down-conversion. By making the optimum joint measurement on the light received from the target region together with the retained spontaneous parametric down-conversion idler beam, the quantum-illumination system realizes a 6 dB advantage in the error-probability exponent over the optimum reception coherent-state system. This advantage accrues despite there being no entanglement between the light collected from the target region and the retained idler beam.

Controllable all-fiber generation/conversion of circularly polarized orbital angular momentum beams using long period fiber gratings

NASA Astrophysics Data System (ADS)

Han, Ya; Liu, Yan-Ge; Wang, Zhi; Huang, Wei; Chen, Lei; Zhang, Hong-Wei; Yang, Kang

2018-01-01

Mode-division multiplexing (MDM) is a promising technology for increasing the data-carrying capacity of a single few-mode optical fiber. The flexible mode manipulation would be highly desired in a robust MDM network. Recently, orbital angular momentum (OAM) modes have received wide attention as a new spatial mode basis. In this paper, we firstly proposed a long period fiber grating (LPFG) system to realize mode conversions between the higher order LP core modes in four-mode fiber. Based on the proposed system, we, for the first time, demonstrate the controllable all-fiber generation and conversion of the higher order LP core modes to the first and second order circularly polarized OAM beams with all the combinations of spin and OAM. Therefore, the proposed LPFG system can be potentially used as a controllable higher order OAM beam switch and a physical layer of the translating protocol from the conventional LP modes communication to the OAM modes communication in the future mode carrier telecommunication system and light calculation protocols.

Analyses of conversion efficiency in high-speed clock recovery based on Mach-Zehnder modulator

NASA Astrophysics Data System (ADS)

Dong, H.; Sun, H.; Zhu, G.; Dutta, N. K.

2006-09-01

In this paper, detailed analyses of the conversion efficiency in high-speed clock recovery based on Mach-Zehnder (MZ) modulator has been carried out. The theoretical results show the conversion efficiency changes with RF driving power and the mixing order. For high order clock recovery, the cascaded MZ modulator provides higher conversion efficiency. A study of clock recovery at 160 Gb/s using the cascaded MZ modulator has been carried out. The experimental results agree with the results of the analysis.

Space-based solar power generation using a distributed network of satellites and methods for efficient space power transmission

NASA Astrophysics Data System (ADS)

McLinko, Ryan M.; Sagar, Basant V.

2009-12-01

Space-based solar power (SSP) generation is being touted as a solution to our ever-increasing energy consumption and dependence on fossil fuels. Satellites in Earth's orbit can capture solar energy through photovoltaic cells and transmit that power to ground based stations. Solar cells in orbit are not hindered by weather, clouds, or night. The energy generated by this process is clean and pollution-free. Although the concept of space-based solar power was initially proposed nearly 40 years ago, the level of technology in photovoltaics, power transmission, materials, and efficient satellite design has finally reached a level of maturity that makes solar power from space a feasible prospect. Furthermore, new strategies in methods for solar energy acquisition and transmission can lead to simplifications in design, reductions in cost and reduced risk. This paper proposes using a distributed array of small satellites to collect power from the Sun, as compared to the more traditional SSP design that consists of one monolithic satellite. This concept mitigates some of SSP's most troublesome historic constraints, such as the requirement for heavy lift launch vehicles and the need for significant assembly in space. Instead, a larger number of smaller satellites designed to collect solar energy are launched independently. A high frequency beam will be used to aggregate collected power into a series of transmission antennas, which beam the energy to Earth's surface at a lower frequency. Due to the smaller power expectations of each satellite and the relatively short distance of travel from low earth orbit, such satellites can be designed with smaller arrays. The inter-satellite rectenna devices can also be smaller and lighter in weight. Our paper suggests how SSP satellites can be designed small enough to fit within ESPA standards and therefore use rideshare to achieve orbit. Alternatively, larger versions could be launched on Falcon 9s or on Falcon 1s with booster stages. The only satellites that are constrained to a significant mass are the beam-down satellites, which still require significant transmission arrays to sufficiently focus the beams targeting corresponding ground stations. With robust design and inherent redundancy built-in, power generation and transmission will not be interrupted in the event of mishaps like space debris collision. Furthermore, the "plug and play" nature of this system significantly reduces the cost, complexity, and risk of upgrading the system. The distributed nature of smallsat clusters maximizes the use of economies of scale. This approach retains some problems of older designs and introduces additional ones. Mitigations will be explored further. For example, the distributed nature of the system requires very precise coordination between and among satellites and a mature attitude control and determination system. Such a design incorporates multiple beaming stages, which has the potential to reduce overall system efficiency. Although this design eliminates the need for space assembly, it retains the challenge of significant on-orbit deployment of solar and transmission arrays. Space power "beaming" is a three step process that involves: 1) conversion of dc power generated by solar cells on the satellite into an electromagnetic wave of suitable frequency, 2) transmission of that wave to power stations on ground, and 3) conversion of the radio waves back into dc power. A great deal of research has been done on the use of microwaves for this purpose. Various factors that affect efficient power generation and transmission will be analyzed in this paper. Based on relevant theory and performance and optimization models, the paper proposes solutions that will help make space-based solar power generation a practical and viable option for addressing the world's growing energy needs.

Dose conversion coefficients based on the Chinese mathematical phantom and MCNP code for external photon irradiation.

PubMed

Qiu, Rui; Li, Junli; Zhang, Zhan; Liu, Liye; Bi, Lei; Ren, Li

2009-02-01

A set of conversion coefficients from kerma free-in-air to the organ-absorbed dose are presented for external monoenergetic photon beams from 10 keV to 10 MeV based on the Chinese mathematical phantom, a whole-body mathematical phantom model. The model was developed based on the methods of the Oak Ridge National Laboratory mathematical phantom series and data from the Chinese Reference Man and the Reference Asian Man. This work is carried out to obtain the conversion coefficients based on this model, which represents the characteristics of the Chinese population, as the anatomical parameters of the Chinese are different from those of Caucasians. Monte Carlo simulation with MCNP code is carried out to calculate the organ dose conversion coefficients. Before the calculation, the effects from the physics model and tally type are investigated, considering both the calculation efficiency and precision. In the calculation irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational and isotropic geometries. Conversion coefficients from this study are compared with those recommended in the Publication 74 of International Commission on Radiological Protection (ICRP74) since both the sets of data are calculated with mathematical phantoms. Overall, consistency between the two sets of data is observed and the difference for more than 60% of the data is below 10%. However, significant deviations are also found, mainly for the superficial organs (up to 65.9%) and bone surface (up to 66%). The big difference of the dose conversion coefficients for the superficial organs at high photon energy could be ascribed to kerma approximation for the data in ICRP74. Both anatomical variations between races and the calculation method contribute to the difference of the data for bone surface.

Beam position monitoring system at CESR

NASA Astrophysics Data System (ADS)

Billing, M. G.; Bergan, W. F.; Forster, M. J.; Meller, R. E.; Rendina, M. C.; Rider, N. T.; Sagan, D. C.; Shanks, J.; Sikora, J. P.; Stedinger, M. G.; Strohman, C. R.; Palmer, M. A.; Holtzapple, R. L.

2017-09-01

The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode, labeled CESRTA (CESR as a Test Accelerator), included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CESRTA occurred over a several year period and is described elsewhere. As a part of this conversion the CESR beam position monitoring (CBPM) system was completely upgraded to provide the needed instrumental capabilities for these studies. This paper describes the new CBPM system hardware, its function and representative measurements performed by the upgraded system.

The influence of atmospheric turbulence on partially coherent two-photon entangled field

NASA Astrophysics Data System (ADS)

Qiu, Y.; She, W.

2012-09-01

The propagation of a two-photon field from down-conversion of a partially coherent Gaussian Schell-model (GSM) pump beam in free space has been reported. However, the propagation of this two-photon field through a turbulent atmosphere has not been investigated yet. In this paper, an analytical expression of the coincidence count rate of the two-photon entangled field is derived. Unlike what has been reported, the field is from a parameter down-conversion of a partially coherent dark hollow pump beam and propagates through a turbulent atmosphere. The effects of the propagation parameters on the coincidence count rate are evaluated and illustrated. The results show that the pump beam parameters and atmospheric turbulence can evidently affect the detection probability of the photon pair at two different positions. It is found that the detection probability of the two-photon field is higher, and thus less susceptible to turbulence, if the field is produced by a lower mode of partially coherent pump beam.

High-efficiency 20 GHz traveling wave tube development for space communications

NASA Technical Reports Server (NTRS)

Aldana, S. L.; Tamashiro, R. N.

1991-01-01

A 75 watt CW high efficiency helix TWT operating at 20 GHz was developed for satellite communication systems. The purpose was to extend the performance capabilities of helix TWTs by using recent technology developments. The TWT described is a unique design because high overall efficiency is obtained with a low perveance beam. In the past, low perveance designs resulted in low beam efficiencies. However, due to recent breakthoughs in diamond rod technology and in collector electrode materials, high efficiencies can now be achieved with low perveance beams. The advantage of a low perveance beam is a reduction in space charge within the beam which translates to more efficient collector operation. In addition, this design incorporates textured graphite electrodes which further enhance collector operation by suppressing backstreaming secondaries. The diamond supported helix circuit features low RF losses, high interaction impedance, good thermal handling capability and has been designed to compensate for the low perveance beam. One more discussed tube feature is the use of a velocity taper in the output helix that achieves low signal distortion while maintaining high efficiency.

Ag Nanoparticle-Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells.

PubMed

Rho, Won-Yeop; Chun, Myeung-Hwan; Kim, Ho-Sub; Kim, Hyung-Mo; Suh, Jung Sang; Jun, Bong-Hyun

2016-06-15

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array-based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array-based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component-Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays-enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency.

Experimental Demonstration of a Highly Efficient Fan-out Polarization Grating

PubMed Central

Wan, Chenhao; Chen, Jian; Tang, Xiahui; Zhan, Qiwen

2016-01-01

Highly efficient fan-out elements are crucial in coherent beam combining architectures especially in coupled laser resonators where the beam passes through the fan-out element twice per round trip. Although the theoretical efficiency is usually less than 86%, the Dammann gratings are ubiquitously utilized in a variety of types of coherent beam combining systems due to the facile design and fabrication. In the current paper, we experimentally demonstrate a highly efficient fan-out polarization grating. It is the first time to our knowledge that all the three space-variant parameters of a polarization grating are simultaneously optimized to achieve the function of multi-beam splitting. Besides the high fan-out efficiency, the ability to control the polarization states of individual split beams is another advantage of this polarization grating. The novel polarization grating is promising to find applications in laser beam combining systems. PMID:28008972

Limits to solar power conversion efficiency with applications to quantum and thermal systems

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.; Smith, B. T.

1983-01-01

An analytical framework is presented that permits examination of the limit to the efficiency of various solar power conversion devices. Thermodynamic limits to solar power efficiency are determined for both quantum and thermal systems, and the results are applied to a variety of devices currently considered for use in space systems. The power conversion efficiency for single-threshold energy quantum systems receiving unconcentrated air mass zero solar radiation is limited to 31 percent. This limit applies to photovoltaic cells directly converting solar radiation, or indirectly, as in the case of a thermophotovoltaic system. Photoelectrochemical cells rely on an additional chemical reaction at the semiconductor-electrolyte interface, which introduces additional second-law demands and a reduction of the solar conversion efficiency. Photochemical systems exhibit even lower possible efficiencies because of their relatively narrow absorption bands. Solar-powered thermal engines in contact with an ambient reservoir at 300 K and operating at maximum power have a peak conversion efficiency of 64 percent, and this occurs for a thermal reservoir at a temperature of 2900 K. The power conversion efficiency of a solar-powered liquid metal magnetohydrodydnamic generator, a solar-powered steam turbine electric generator, and an alkali metal thermoelectric converter is discussed.

The LICPA-driven collider—a novel efficient tool for the production of ultra-high pressures in condensed media

NASA Astrophysics Data System (ADS)

Badziak, J.; Krousky, E.; Kucharik, M.; Liska, R.

2016-03-01

Generation of strong shock waves for the production of Mbar or Gbar pressures is a topic of high relevance for contemporary research in various domains, including inertial confinement fusion, laboratory astrophysics, planetology and material science. The pressures in the multi-Mbar range can be produced by the shocks generated using chemical explosions, light-gas guns, Z-pinch machines or lasers. Higher pressures, in the sub-Gbar or Gbar range are attainable only with nuclear explosions or laser-based methods. Unfortunately, due to the low efficiency of energy conversion from a laser to the shock (below a few percent), multi-kJ, multi-beam lasers are needed to produce such pressures with these methods. Here, we propose and investigate a novel scheme for generating high-pressure shocks which is much more efficient than the laser-based schemes known so far. In the proposed scheme, the shock is generated in a dense target by the impact of a fast projectile driven by the laser-induced cavity pressure acceleration (LICPA) mechanism. Using two-dimensional hydrodynamic simulations and the measurements performed at the kilojoule PALS laser facility it is shown that in the LICPA-driven collider the laser-to-shock energy conversion efficiency can reach a very high value ~ 15-20 % and, as a result, the shock pressure ~ 0.5-1 Gbar can be produced using lasers of energy <= 0.5 kJ. On the other hand, the pressures in the multi-Mbar range could be produced in this collider with low-energy (~ 10 J) lasers available on the market. It would open up the possibility of conducting research in high energy-density science also in small, university-class laboratories.

Effects of quaternary ammonium-methacrylates on the mechanical properties of unfilled resins.

PubMed

Hoshika, Tomohiro; Nishitani, Yoshihiro; Yoshiyama, Masahiro; Key, William O; Brantley, William; Agee, Kelli A; Breschi, Lorenzo; Cadenaro, Milena; Tay, Franklin R; Rueggeberg, Frederick; Pashley, David H

2014-11-01

Adding antimicrobial/anti-MMP quaternary ammonium methacrylates (QAMs) to comonomer blends should not weaken the mechanical properties of dental resins. This work evaluated the degree conversion and mechanical properties of BisGMA/TEGDMA/HEMA (60:30:10) containing 0-15 mass% QAMs A-E (A: 2-acryloxyethyltrimethyl ammonium chloride; B: [3-(methacryloylamino)propyl]trimethylammonium chloride; C: [2-(methacryloxy)ethyl] trimethyl ammonium chloride; D: diallyldimethyl ammonium chloride; E: 2-(methacryloyloxy) ethyltrimethyl ammonium methyl sulfate. Unfilled resins with and without QAM were placed on ATR-FTIR and light-polymerized for 20s in a thin film at 30°C. Unfilled resin beams were casted from square hollow glass tubings. Half of the beams were tested after 3 days of drying (control); the other half were tested wet after 3 days of water storage. Addition of QAMs in control resins significantly increased conversion 600 s after light termination, with the exception of 5% MAPTAC (p<0.05). Increase of QAM content within a formulation significantly increased conversion. Control beams gave dry Young's moduli of ∼700 MPa. Addition of 5, 10 or 15 mass% QAMs produced significant reductions in dry Young's moduli except for 5% B or C. 15 mass% A, B and C lowered the wet Young's moduli of the resin beams by more than 30%. The ultimate tensile stress (UTS) of control dry resin was 89±11 MPa. Addition of 5-10 mass% QAMs had no adverse effect on the dry UTS. After water storage, the UTS of all resin blends fell significantly (p<0.05), especially when 15 wt% QAMs was added. Control dry beams gave fracture toughness (KIC) values of 0.88±0.1 MPa m(1/2). Wet values were significantly higher at 1.02±0.06 (p<0.05). KIC of dry beams varied from 0.85±0.08 at 5% QAMs to 0.49±0.05 at 15% QAMs. Wet beams gave KIC values of 1.02±0.06 MPa m(1/2) that fell to 0.23±0.01 at 15% QAMs. Addition of 10% QAMs increased the degree of conversion of unfilled resins, but lowered wet toughness and UTS; addition of 15% QAMs lowered the mechanical properties of wet resins below acceptable levels. Copyright © 2014 Academy of Dental Materials. All rights reserved.

Investigation for all polarization conversions of the guided-modes in a bending waveguide

NASA Astrophysics Data System (ADS)

Shi, Yunjie; Shang, Hongpeng; Sun, DeGui

2018-03-01

In this work, a new solution to the partial differential Maxwell equations is first derived to investigate all polarization conversions of the transverse and the longitudinal components of guided-modes in a bending waveguide. Then, for the silica-waveguides, the polarization conversion efficiencies are numerical calculated and a significant finding is that the transverse-longitudinal polarization conversion efficiency is much higher than that of transverse-transverse polarization conversion. Furthermore, the dependences of all the conversion efficiencies on waveguide parameters are found. The agreeable results between the numerical calculation and the finite difference time-domain (FDTD) simulation show that for two 100 μm long bending waveguides of 0.75 and 1.50% index contrasts, the amplitude conversion efficiencies from ∼10-3 to ∼10-2 can be realized for the transverse-transverse polarization components and that of ∼10-1 can be realized for the transverse-longitudinal polarization components.

Frequency Up-Conversion Photon-Type Terahertz Imager.

PubMed

Fu, Z L; Gu, L L; Guo, X G; Tan, Z Y; Wan, W J; Zhou, T; Shao, D X; Zhang, R; Cao, J C

2016-05-05

Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices.

Frequency Up-Conversion Photon-Type Terahertz Imager

PubMed Central

Fu, Z. L.; Gu, L. L.; Guo, X. G.; Tan, Z. Y.; Wan, W. J.; Zhou, T.; Shao, D. X.; Zhang, R.; Cao, J. C.

2016-01-01

Terahertz imaging has many important potential applications. Due to the failure of Si readout integrated circuits (ROICs) and the thermal mismatch between the photo-detector arrays and the ROICs at temperatures below 40 K, there are big technical challenges to construct terahertz photo-type focal plane arrays. In this work, we report pixel-less photo-type terahertz imagers based on the frequency up-conversion technique. The devices are composed of terahertz quantum-well photo-detectors (QWPs) and near-infrared (NIR) light emitting diodes (LEDs) which are grown in sequence on the same substrates using molecular beam epitaxy. In such an integrated QWP-LED device, photocurrent in the QWP drives the LED to emit NIR light. By optimizing the structural parameters of the QWP-LED, the QWP part and the LED part both work well. The maximum values of the internal and external energy up-conversion efficiencies are around 20% and 0.5%. A laser spot of a homemade terahertz quantum cascade laser is imaged by the QWP-LED together with a commercial Si camera. The pixel-less imaging results show that the image blurring induced by the transverse spreading of photocurrent is negligible. The demonstrated pixel-less imaging opens a new way to realize high performance terahertz imaging devices. PMID:27147281

Comparison of the Al back contact deposited by sputtering, e-beam, or thermal evaporation for inverted perovskite solar cells

NASA Astrophysics Data System (ADS)

Wahl, Tina; Hanisch, Jonas; Ahlswede, Erik

2018-04-01

In this work, we present inverted perovskite solar cells with Al top electrodes, which were deposited by three different methods. Besides the widely used thermal evaporation of Al, we also used the industrially important high deposition rate processes sputtering and electron beam evaporation for aluminium electrodes and examined the influence of the deposition method on the solar cell performance. The current-voltage characteristics of as grown solar cells with sputtered and e-beam Al electrode show an s-shape due to damage done to the organic electronic transport layers (ETL) during Al deposition. It can be cured by a short annealing step at a moderate temperature so that fill factors  >60% and power conversion efficiencies of almost 12% with negligible hysteresis can be achieved. While solar cells with thermally evaporated Al electrode do not show an s-shape, they also exhibit a clear improvement after a short annealing step. In addition, we varied the thickness of the ETL consisting of a double layer ([6,6]-Phenyl-C61-butyric acid methyl ester and bathocuproine) and investigated the influence on the solar cell parameters for the three different Al deposition methods, which showed distinct dependencies on ETL thickness.

Dual-beam laser autofocusing system based on liquid lens

NASA Astrophysics Data System (ADS)

Zhang, Fumin; Yao, Yannan; Qu, Xinghua; Zhang, Tong; Pei, Bing

2017-02-01

A dual-beam laser autofocusing system is designed in this paper. The autofocusing system is based on a liquid lens with less moving parts and fast response time, which makes the system simple, reliable, compact and fast. A novel scheme ;Time-sharing focus, fast conversion; is innovatively proposed. The scheme effectively solves the problem that the guiding laser and the working laser cannot focus at the same target point because of the existence of chromatic aberration. This scheme not only makes both guiding laser and working laser achieve optimal focusing in guiding stage and working stage respectively, but also greatly reduces the system complexity and simplifies the focusing process as well as makes autofocusing time of the working laser reduce to about 10 ms. In the distance range of 1 m to 30 m, the autofocusing spot size is kept under 4.3 mm at 30 m and just 0.18 mm at 1 m. The spot size is much less influenced by the target distance compared with the collimated laser with a micro divergence angle for its self-adaptivity. The dual-beam laser autofocusing system based on liquid lens is fully automatic, compact and efficient. It is fully meet the need of dynamicity and adaptivity and it will play an important role in a number of long-range control applications.

Investigation of real tissue water equivalent path lengths using an efficient dose extinction method

NASA Astrophysics Data System (ADS)

Zhang, Rongxiao; Baer, Esther; Jee, Kyung-Wook; Sharp, Gregory C.; Flanz, Jay; Lu, Hsiao-Ming

2017-07-01

For proton therapy, an accurate conversion of CT HU to relative stopping power (RSP) is essential. Validation of the conversion based on real tissue samples is more direct than the current practice solely based on tissue substitutes and can potentially address variations over the population. Based on a novel dose extinction method, we measured water equivalent path lengths (WEPL) on animal tissue samples to evaluate the accuracy of CT HU to RSP conversion and potential variations over a population. A broad proton beam delivered a spread out Bragg peak to the samples sandwiched between a water tank and a 2D ion-chamber detector. WEPLs of the samples were determined from the transmission dose profiles measured as a function of the water level in the tank. Tissue substitute inserts and Lucite blocks with known WEPLs were used to validate the accuracy. A large number of real tissue samples were measured. Variations of WEPL over different batches of tissue samples were also investigated. The measured WEPLs were compared with those computed from CT scans with the Stoichiometric calibration method. WEPLs were determined within  ±0.5% percentage deviation (% std/mean) and  ±0.5% error for most of the tissue surrogate inserts and the calibration blocks. For biological tissue samples, percentage deviations were within  ±0.3%. No considerable difference (<1%) in WEPL was observed for the same type of tissue from different sources. The differences between measured WEPLs and those calculated from CT were within 1%, except for some bony tissues. Depending on the sample size, each dose extinction measurement took around 5 min to produce ~1000 WEPL values to be compared with calculations. This dose extinction system measures WEPL efficiently and accurately, which allows the validation of CT HU to RSP conversions based on the WEPL measured for a large number of samples and real tissues.

EBW H&CD Potential for Spherical Tokamaks

NASA Astrophysics Data System (ADS)

Urban, J.; Decker, J.; Peysson, Y.; Preinhaelter, J.; Shevchenko, V.; Taylor, G.; Vahala, L.; Vahala, G.

2011-12-01

Spherical tokamaks (STs), which feature relatively high neutron flux and good economy, operate generally in high-ß regimes, in which the usual EC O- and X- modes are cut-off. In this case, electron Bernstein waves (EBWs) seem to be the only option that can provide features similar to the EC waves—controllable localized heating and current drive (H&) that can be utilized for core plasma heating as well as for accurate plasma stabilization. We first derive an analytical expression for Gaussian beam OXB conversion efficiency. Then, an extensive numerical study of EBW H&CD performance in four typical ST plasmas (NSTX L- and H-mode, MAST Upgrade, NHTX) is performed. Coupled ray-tracing (AMR) and Fokker-Planck (LUKE) codes are employed to simulate EBWs of varying frequencies and launch conditions. Our results indicate that an efficient and universal EBW H&CD system is indeed viable. In particular, power can be deposited and current reasonably efficiently driven across the whole plasma radius. Such a system could be controlled by a suitably chosen launching antenna vertical position and would also be sufficiently robust.

Electron-beam lithography with character projection exposure for throughput enhancement with line-edge quality optimization

NASA Astrophysics Data System (ADS)

Ikeno, Rimon; Maruyama, Satoshi; Mita, Yoshio; Ikeda, Makoto; Asada, Kunihiro

2016-03-01

Among various electron-beam lithography (EBL) techniques, variable-shaped beam (VSB) and character projection (CP) methods have attracted many EBL users for their high-throughput feature, but they are considered to be more suited to small-featured VLSI fabrication with regularly-arranged layouts like standard-cell logics and memory arrays. On the other hand, non-VLSI applications like photonics, MEMS, MOEMS, and so on, have not been fully utilized the benefit of CP method due to their wide variety of layout patterns. In addition, the stepwise edge shapes by VSB method often causes intolerable edge roughness to degrade device characteristics from its intended performance with smooth edges. We proposed an overall EBL methodology applicable to wade-variety of EBL applications utilizing VSB and CP methods. Its key idea is in our layout data conversion algorithm that decomposes curved or oblique edges of arbitrary layout patterns into CP shots. We expect significant reduction in EB shot count with a CP-bordered exposure data compared to the corresponding VSB-alone conversion result. Several CP conversion parameters are used to optimize EB exposure throughput, edge quality, and resultant device characteristics. We demonstrated out methodology using the leading-edge VSB/CP EBL tool, ADVANTEST F7000S-VD02, with high resolution Hydrogen Silsesquioxane (HSQ) resist. Through our experiments of curved and oblique edge lithography under various data conversion conditions, we learned correspondence of the conversion parameters to the resultant edge roughness and other conditions. They will be utilized as the fundamental data for further enhancement of our EBL strategy for optimized EB exposure.

Controlling Second Harmonic Efficiency of Laser Beam Interactions

NASA Technical Reports Server (NTRS)

Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

2011-01-01

A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

High efficiency single transverse mode photonic band crystal lasers with low vertical divergence

NASA Astrophysics Data System (ADS)

Zhao, Shaoyu; Qu, Hongwei; Liu, Yun; Li, Lunhua; Chen, Yang; Zhou, Xuyan; Lin, Yuzhe; Liu, Anjin; Qi, Aiyi; Zheng, Wanhua

2016-10-01

High efficiency 980 nm longitudinal photonic band crystal (PBC) edge emitting laser diodes are designed and fabricated. The calculated results show that eight periods of Al0.1Ga0.9As and Al0.25Ga0.75As layer pairs can reduce the vertical far field divergence to 10.6° full width at half maximum (FWHM). The broad area (BA) lasers show a very high internal quantum efficiency ηi of 98% and low internal loss αi of 1.92 cm-1. Ridge waveguide (RW) lasers with 3 mm cavity length and 5um strip width provide 430 mW stable single transverse mode output at 500 mA injection current with power conversion efficiency (PCE) of 47% under continuous wave (CW) mode. A maximum PCE of 50% is obtained at the 300 mA injection current. A very low vertical far field divergence of 9.4° is obtained at 100 mA injection. At 500 mA injection, the vertical far field divergence increases to 11°, the beam quality factors M2 values are 1.707 in vertical direction and 1.769 in lateral direction.

Enhanced tunable narrow-band THz emission from laser-modulated electron beams

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

Xiang, D.; Stupakov, G.; /SLAC

2009-06-19

We propose and analyze a scheme to generate enhanced narrow-band terahertz (THz) radiation through down-conversion of the frequency of optical lasers using laser-modulated electron beams. In the scheme the electron beam is first energy modulated by two lasers with wave numbers k{sub 1} and k2, respectively. After passing through a dispersion section, the energy modulation is converted to density modulation. Due to the nonlinear conversion process, the beam will have density modulation at wave number k = nk{sub 1} + mk{sub 2}, where n and m are positive or negative integers. By properly choosing the parameters for the lasers andmore » dispersion section, one can generate density modulation at THz frequency in the beam using optical lasers. This density-modulated beam can be used to generate powerful narrow-band THz radiation. Since the THz radiation is in tight synchronization with the lasers, it should provide a high temporal resolution for the optical-pump THz-probe experiments. The central frequency of the THz radiation can be easily tuned by varying the wavelength of the two lasers and the energy chirp of the electron beam. The proposed scheme is in principle able to generate intense narrow-band THz radiation covering the whole THz range and offers a promising way towards the tunable intense narrow-band THz sources.« less

Wave front engineering by means of diffractive optical elements for applications in microscopy

NASA Astrophysics Data System (ADS)

Cojoc, Dan; Ferrari, Enrico; Garbin, Valeria; Cabrini, Stefano; Carpentiero, Alessandro; Prasciolu, Mauro; Businaro, Luca; Kaulich, Burchard; Di Fabrizio, Enzo

2006-05-01

We present a unified view regarding the use of diffractive optical elements (DOEs) for microscopy applications a wide range of electromagnetic spectrum. The unified treatment is realized through the design and fabrication of DOE through which wave front beam shaping is obtained. In particular we show applications ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy. We report some details on the design and physical implementation of diffractive elements that beside focusing perform also other optical functions: beam splitting, beam intensity and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of spherical micro beads and for direct trapping and manipulation of biological cells with non-spherical shapes. Another application is the Gauss to Laguerre-Gaussian mode conversion, which allows to trap and transfer orbital angular momentum of light to micro particles with high refractive index and to trap and manipulate low index particles. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for DOEs implementation. High resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in X-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field X-ray microscopy.

Optical distance measurement device and method thereof

DOEpatents

Bowers, Mark W.

2003-05-27

A system and method of efficiently obtaining distance measurements of a target. A modulated optical beam may be used to determine the distance to the target. A first beam splitter may be used to split the optical beam and a second beam splitter may be used to recombine a reference beam with a return ranging beam. An optical mixing detector may be used in a receiver to efficiently detect distance measurement information.

Magnetogasdynamic Power Extraction and Flow Conditioning for a Gas Turbine

NASA Technical Reports Server (NTRS)

Adamovich, Igor V.; Rich, J. William; Schneider, Steven; Blankson, Isaiah

2003-01-01

An extension of the Russian AJAX concept to a turbojet is being explored. This magnetohydrodynamic (MHD) energy bypass engine cycle incorporating conventional gas turbine technology has MHD flow conditioning at the inlet to electromagnetically extract part of the inlet air kinetic energy. The electrical power generated can be used for various on-board vehicle requirements including plasma flow control around the vehicle or it may be used for augmenting the expanding flow in the high speed nozzle by MHD forces to generate more thrust. In order to achieve this interaction, the air needs to be ionized by an external means even up to fairly high flight speeds, and the leading candidates may be classified as electrical discharge devices. The present kinetic modeling calculations suggest that the use of electron beams with characteristics close to the commercially available e-beam systems (electron energy approx. 60 keV, beam current approx. 0.2 mA/sq cm) to sustain ionization in intermediate pressure, low-temperature (P = 0.1 atm, T = 300 K) supersonic air flows allows considerable reduction of the flow kinetic energy (up to 10 to 20 percent in M = 3 flows). The calculations also suggest that this can be achieved at a reasonable electron beam efficiency (eta approx. 5), even if the e-beam window losses are taken into account. At these conditions, the exit NO and O atom concentrations due to e-beam initiated chemical reactions do not exceed 30 ppm. Increasing the beam current up to approx. 2 mA/sq cm, which corresponds to a maximum electrical conductivity of sigma(sub max) approx. 0.8 mho/m at the loading parameter of K = 0.5, would result in a much greater reduction of the flow kinetic energy (up to 30 to 40 percent). The MHD channel efficiency at these conditions would be greatly reduced (to eta approx. 1) due to increased electron recombination losses in the channel. At these conditions, partial energy conversion from kinetic energy to heat would result in a significant total pressure loss (P(sub 0)/P(sub 0i) approx. 0.3). The total pressure loss can be reduced operating at the loading parameter closer to unity, at the expense of the reduced electrical power output. Raising the beam current would also result in the increase of the exit O atom concentrations (up to 600 ppm) and NO (up to 150 ppm).

Silicon trench photodiodes on a wafer for efficient X-ray-to-current signal conversion using side-X-ray-irradiation mode

NASA Astrophysics Data System (ADS)

Ariyoshi, Tetsuya; Takane, Yuta; Iwasa, Jumpei; Sakamoto, Kenji; Baba, Akiyoshi; Arima, Yutaka

2018-04-01

In this paper, we report a direct-conversion-type X-ray sensor composed of trench-structured silicon photodiodes, which achieves a high X-ray-to-current conversion efficiency under side X-ray irradiation. The silicon X-ray sensor with a length of 22.6 mm and a trench depth of 300 µm was fabricated using a single-poly single-metal 0.35 µm process. X-rays with a tube voltage of 80 kV were irradiated along the trench photodiode from the side of the test chip. The theoretical limit of X-ray-to-current conversion efficiency of 83.8% was achieved at a low reverse bias voltage of 25 V. The X-ray-to-electrical signal conversion efficiency of conventional indirect-conversion-type X-ray sensors is about 10%. Therefore, the developed sensor has a conversion efficiency that is about eight times higher than that of conventional sensors. It is expected that the developed X-ray sensor will be able to markedly lower the radiation dose required for X-ray diagnoses.

Estimating Hardwood Sawmill Conversion Efficiency Based on Sawing Machine and Log.

Treesearch

Michael W. Wade; Steven H. Bullard; Philip H. Steele; Philip A. Araman

1992-01-01

Increased problems of hardwood timber availability have caused many sawmillers, industry analysts, and planners to recognize the importance of sawmill conversion efficiency. Conversion efficiency not only affects sawmill profits, but is also important on a much broader level. Timber supply issues have caused resource planners and policy makers to consider the effects...

Current matching using CdSe quantum dots to enhance the power conversion efficiency of InGaP/GaAs/Ge tandem solar cells.

PubMed

Lee, Ya-Ju; Yao, Yung-Chi; Tsai, Meng-Tsan; Liu, An-Fan; Yang, Min-De; Lai, Jiun-Tsuen

2013-11-04

A III-V multi-junction tandem solar cell is the most efficient photovoltaic structure that offers an extremely high power conversion efficiency. Current mismatching between each subcell of the device, however, is a significant challenge that causes the experimental value of the power conversion efficiency to deviate from the theoretical value. In this work, we explore a promising strategy using CdSe quantum dots (QDs) to enhance the photocurrent of the limited subcell to match with those of the other subcells and to enhance the power conversion efficiency of InGaP/GaAs/Ge tandem solar cells. The underlying mechanism of the enhancement can be attributed to the QD's unique capacity for photon conversion that tailors the incident spectrum of solar light; the enhanced efficiency of the device is therefore strongly dependent on the QD's dimensions. As a result, by appropriately selecting and spreading 7 mg/mL of CdSe QDs with diameters of 4.2 nm upon the InGaP/GaAs/Ge solar cell, the power conversion efficiency shows an enhancement of 10.39% compared to the cell's counterpart without integrating CdSe QDs.

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

NASA Astrophysics Data System (ADS)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-03-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

NASA Astrophysics Data System (ADS)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-06-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Nonlinear polarization rotation and orthogonal polarization generation experienced in a single-beam configuration

NASA Astrophysics Data System (ADS)

Minkovski, N.; Petrov, G. I.; Saltiel, S. M.; Albert, O.; Etchepare, J.

2004-09-01

Nonlinear polarization rotation and generation of a polarization component orthogonal to the input beam were observed along fourfold axes of YVO4 and BaF2 crystals. We demonstrate experimentally that in both crystals the angle of rotation is proportional, at low intensities, to the square of the product of the input intensity and the crystal length and is the result of simultaneous action of two third-order processes. This type of nonlinear polarization rotation is driven by the real part of the cubic susceptibility. The recorded energy exchange between the two orthogonal components can exceed 10%. It is to our knowledge the highest energy-conversion efficiency achieved in a single beam nonresonant χ(3) interaction. A simple theoretical model is elaborated to describe the dependence of nonlinear polarization rotation and orthogonal polarization generation on the intensity of the input beam at both low- and high-intensity levels. It reveals the potential contributions from the real and the imaginary parts of the susceptibility tensor. Moreover, this kind of measurement is designed to permit the determination of the magnitude and the sign of the anisotropy of the real part of third-order nonlinearity in crystals with cubic or tetragonal symmetry on the basis of polarization-rotation measurements. The χxxxx(3) component of the third-order susceptibility tensor and its anisotropy sign and amplitude value for BaF2 and YVO4 crystals are estimated and discussed.

Novel Cavities in Vertical External Cavity Surface Emitting Lasers for Emission in Broad Spectral Region by Means of Nonlinear Frequency Conversion

NASA Astrophysics Data System (ADS)

Lukowski, Michal L.

Optically pumped semiconductor vertical external cavity surface emitting lasers (VECSEL) were first demonstrated in the mid 1990's. Due to the unique design properties of extended cavity lasers VECSELs have been able to provide tunable, high-output powers while maintaining excellent beam quality. These features offer a wide range of possible applications in areas such as medicine, spectroscopy, defense, imaging, communications and entertainment. Nowadays, newly developed VECSELs, cover the spectral regions from red (600 nm) to around 5 microm. By taking the advantage of the open cavity design, the emission can be further expanded to UV or THz regions by the means of intracavity nonlinear frequency generation. The objective of this dissertation is to investigate and extend the capabilities of high-power VECSELs by utilizing novel nonlinear conversion techniques. Optically pumped VECSELs based on GaAs semiconductor heterostructures have been demonstrated to provide exceptionally high output powers covering the 900 to 1200 nm spectral region with diffraction limited beam quality. The free space cavity design allows for access to the high intracavity circulating powers where high efficiency nonlinear frequency conversions and wavelength tuning can be obtained. As an introduction, this dissertation consists of a brief history of the development of VECSELs as well as wafer design, chip fabrication and resonator cavity design for optimal frequency conversion. Specifically, the different types of laser cavities such as: linear cavity, V-shaped cavity and patented T-shaped cavity are described, since their optimization is crucial for transverse mode quality, stability, tunability and efficient frequency conversion. All types of nonlinear conversions such as second harmonic, sum frequency and difference frequency generation are discussed in extensive detail. The theoretical simulation and the development of the high-power, tunable blue and green VECSEL by the means of type I second harmonic generation in a V- cavity is presented. Tens of watts of output power for both blue and green wavelengths prove the viability for VECSELs to replace the other types of lasers currently used for applications in laser light shows, for Ti:Sapphire pumping, and for medical applications such as laser skin resurfacing. The novel, recently patented, two-chip T-cavity configuration allowing for spatial overlap of two, separate VECSEL cavities is described in detail. This type of setup is further used to demonstrate type II sum frequency generation to green with multi-watt output, and the full potential of the T-cavity is utilized by achieving type II difference frequency generation to the mid-IR spectral region. The tunable output around 5.4 microm with over 10 mW power is showcased. In the same manner the first attempts to generate THz radiation are discussed. Finally, a slightly modified T-cavity VECSEL is used to reach the UV spectral regions thanks to type I fourth harmonic generation. Over 100 mW at around 265 nm is obtained in a setup which utilizes no stabilization techniques. The dissertation demonstrates the flexibility of the VECSEL in achieving broad spectral coverage and thus its potential for a wide range of applications.

High speed real-time wavefront processing system for a solid-state laser system

NASA Astrophysics Data System (ADS)

Liu, Yuan; Yang, Ping; Chen, Shanqiu; Ma, Lifang; Xu, Bing

2008-03-01

A high speed real-time wavefront processing system for a solid-state laser beam cleanup system has been built. This system consists of a core2 Industrial PC (IPC) using Linux and real-time Linux (RT-Linux) operation system (OS), a PCI image grabber, a D/A card. More often than not, the phase aberrations of the output beam from solid-state lasers vary fast with intracavity thermal effects and environmental influence. To compensate the phase aberrations of solid-state lasers successfully, a high speed real-time wavefront processing system is presented. Compared to former systems, this system can improve the speed efficiently. In the new system, the acquisition of image data, the output of control voltage data and the implementation of reconstructor control algorithm are treated as real-time tasks in kernel-space, the display of wavefront information and man-machine conversation are treated as non real-time tasks in user-space. The parallel processing of real-time tasks in Symmetric Multi Processors (SMP) mode is the main strategy of improving the speed. In this paper, the performance and efficiency of this wavefront processing system are analyzed. The opened-loop experimental results show that the sampling frequency of this system is up to 3300Hz, and this system can well deal with phase aberrations from solid-state lasers.

Modeling of photoluminescence in laser-based lighting systems

NASA Astrophysics Data System (ADS)

Chatzizyrli, Elisavet; Tinne, Nadine; Lachmayer, Roland; Neumann, Jörg; Kracht, Dietmar

2017-12-01

The development of laser-based lighting systems has been the latest step towards a revolution in illumination technology brought about by solid-state lighting. Laser-activated remote phosphor systems produce white light sources with significantly higher luminance than LEDs. The weak point of such systems is often considered to be the conversion element. The high-intensity exciting laser beam in combination with the limited thermal conductivity of ceramic phosphor materials leads to thermal quenching, the phenomenon in which the emission efficiency decreases as temperature rises. For this reason, the aim of the presented study is the modeling of remote phosphor systems in order to investigate their thermal limitations and to calculate the parameters for optimizing the efficiency of such systems. The common approach to simulate remote phosphor systems utilizes a combination of different tools such as ray tracing algorithms and wave optics tools for describing the incident and converted light, whereas the modeling of the conversion process itself, i.e. photoluminescence, in most cases is circumvented by using the absorption and emission spectra of the phosphor material. In this study, we describe the processes involved in luminescence quantum-mechanically using the single-configurational-coordinate diagram as well as the Franck-Condon principle and propose a simulation model that incorporates the temperature dependence of these processes. Following an increasing awareness of climate change and environmental issues, the development of ecologically friendly lighting systems featuring low power consumption and high luminous efficiency is imperative more than ever. The better understanding of laser-based lighting systems is an important step towards that aim as they may improve on LEDs in the near future.

Spectrally Tailored Pulsed Thulium Fiber Laser System for Broadband Lidar CO2 Sensing

NASA Technical Reports Server (NTRS)

Heaps, William S.; Georgieva, Elena M.; McComb, Timothy S.; Cheung, Eric C.; Hassell, Frank R.; Baldauf, Brian K.

2011-01-01

Thulium doped pulsed fiber lasers are capable of meeting the spectral, temporal, efficiency, size and weight demands of defense and civil applications for pulsed lasers in the eye-safe spectral regime due to inherent mechanical stability, compact "all-fiber" master oscillator power amplifier (MOPA) architectures, high beam quality and efficiency. Thulium fiber's longer operating wavelength allows use of larger fiber cores without compromising beam quality, increasing potential single aperture pulse energies. Applications of these lasers include eye-safe laser ranging, frequency conversion to longer or shorter wavelengths for IR countermeasures and sensing applications with otherwise tough to achieve wavelengths and detection of atmospheric species including CO2 and water vapor. Performance of a portable thulium fiber laser system developed for CO2 sensing via a broadband lidar technique with an etalon based sensor will be discussed. The fielded laser operates with approximately 280 J pulse energy in 90-150ns pulses over a tunable 110nm spectral range and has a uniquely tailored broadband spectral output allowing the sensing of multiple CO2 lines simultaneously, simplifying future potentially space based CO2 sensing instruments by reducing the number and complexity of lasers required to carry out high precision sensing missions. Power scaling and future "all fiber" system configurations for a number of ranging, sensing, countermeasures and other yet to be defined applications by use of flexible spectral and temporal performance master oscillators will be discussed. The compact, low mass, robust, efficient and readily power scalable nature of "all-fiber" thulium lasers makes them ideal candidates for use in future space based sensing applications.

Identification of combustion intermediates in low-pressure premixed pyridine/oxygen/argon flames.

PubMed

Tian, Zhenyu; Li, Yuyang; Zhang, Taichang; Zhu, Aiguo; Qi, Fei

2008-12-25

Combustion intermediates of two low-pressure premixed pyridine/oxygen flames with respective equivalence ratios of 0.56 (C/O/N = 1:4.83:0.20) and 2.10 (C/O/N = 1:1.29:0.20) have been identified with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry techniques. About 80 intermediates in the rich flame and 60 intermediates in the lean flame, including nitrogenous, oxygenated, and hydrocarbon intermediates, have been identified by measurements of photoionization mass spectra and photoionization efficiency spectra. Some radicals and new nitrogenous intermediates are identified in the present work. The experimental results are useful for studying the conversion of volatile nitrogen compounds and understanding the formation mechanism of NO(x) in flames of nitrogenous fuels.

Compact high-pulse-energy passively Q-switched Nd:YLF laser with an ultra-low-magnification unstable resonator: application for efficient optical parametric oscillator.

PubMed

Cho, C Y; Huang, Y P; Huang, Y J; Chen, Y C; Su, K W; Chen, Y F

2013-01-28

We exploit an ultra-low-magnification unstable resonator to develop a high-pulse-energy side-pumped passively Q-switched Nd:YLF/Cr⁴⁺:YAG laser with improving beam quality. A wedged laser crystal is employed in the cavity to control the emissions at 1047 nm and 1053 nm independently through the cavity alignment. The pulse energies at 1047 nm and 1053 nm are found to be 19 mJ and 23 mJ, respectively. The peak powers for both wavelengths are higher than 2 MW. Furthermore, the developed Nd:YLF lasers are employed to pump a monolithic optical parametric oscillator for confirming the applicability in nonlinear wavelength conversions.

Yellow light generation by frequency doubling of a diode-pumped Nd:YAG laser

NASA Astrophysics Data System (ADS)

Jia, Fu-qiang; Zheng, Quan; Xue, Qing-hua; Bu, Yi-kun; Qian, Long-sheng

2006-03-01

We demonstrate the generation of TEM00 mode yellow light in critically type II phase-matched KTiOPO4 (KTP) with intracavity frequency doubling of a diode-pumped Nd:YAG laser at room temperature. After a 150 μm thick etalon have been inserted into the cavity, the stability and beam quality of the second harmonic generation (SHG) is enhanced. A continuous wave (CW) TEM00 mode output power of 1.67 W at 556 nm is obtained at a pump level of 16 W. The total optical to optical conversion efficiency is about 10.44%. To the best of our knowledge, this is the first Watt-level yellow light generation by frequency doubling of Nd:YAG laser.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells

NASA Astrophysics Data System (ADS)

Sahin, Mehmet

2018-05-01

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p–n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy () of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same . The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same , become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

Organic solar cells using a ZnO/Cu/ZnO anode deposited by ion beam sputtering at room temperature for flexible devices.

PubMed

El Hajj, Ahmad; Lucas, Bruno; Barbot, Anthony; Antony, Rémi; Ratier, Bernard; Aldissi, Matt

2013-07-01

The development of indium-free transparent conductive oxides (TCOs) on polymer substrates for flexible devices requires deposition at low temperatures and a limited thermal treatment. In this paper, we investigated the optical and electrical properties of ZnO/Cu/ZnO multi-layer electrodes obtained by ion beam sputtering at room temperature for flexible optoelectronic devices. This multilayer structure has the advantage of adjusting the layer thickness to favor antireflection and surface plasmon resonance of the metallic layer. We found that the optimal electrode is made up of a 10 nm-thick Cu layer between two 40 nm-thick ZnO layers, which results in a sheet resistance of 12 omega/(see symbol), a high transmittance of 85% in the visible range, and the highest figure of merit of 5.4 x 10(-3) (see symbol)/omega. A P3HT:PCBM-based solar cell showed a power conversion efficiency (PCE) of 2.26% using the optimized ZnO (40 nm)/Cu (10 nm)/ZnO (40 nm) anode.

A continuous-wave, widely tunable, intra-cavity, singly resonant, magnesium-doped, periodically poled lithium niobate optical parametric oscillator

NASA Astrophysics Data System (ADS)

Li, Z. P.; Duan, Y. M.; Wu, K. R.; Zhang, G.; Zhu, H. Y.; Wang, X. L.; Chen, Y. H.; Xue, Z. Q.; Lin, Q.; Song, G. C.; Su, H.

2013-05-01

We report a continuous-wave (CW), intra-cavity singly resonant optical parametric oscillator (OPO), based on periodically poled MgO:LiNbO3 pumped by a diode-end-pumped CW Nd:YVO4 laser, and calculate the gain of optical parametric amplification as a function of pump beam waist (at 1064 nm) in the singly resonant OPO (SRO) cavity, to balance the mode-matching and the intensity for the higher gain of a signal wave in the operation of the SRO. In order to achieve maximum gain, we use a convex lens to limit the 1064 nm beam waist. In the experiment, a tunable signal output from 1492 to 1614 nm and an idler output from 3122 to 3709 nm are obtained. For an 808 nm pump power of 11.5 W, a maximum signal output power of up to 2.48 W at 1586 nm and an idler output power of 1.1 W at 3232 nm are achieved with a total optical-to-optical conversion efficiency of 31%.

Quasi-monoenergetic ion generation by hole-boring radiation pressure acceleration in inhomogeneous plasmas using tailored laser pulses

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

Weng, S. M., E-mail: weng-sm@ile.osaka-u.ac.jp; Murakami, M.; Azechi, H.

It is proposed that laser hole-boring at a steady speed in inhomogeneous overdense plasma can be realized by the use of temporally tailored intense laser pulses, producing high-fluence quasi-monoenergetic ion beams. A general temporal profile of such laser pulses is formulated for arbitrary plasma density distribution. As an example, for a precompressed deuterium-tritium fusion target with an exponentially increasing density profile, its matched laser profile for steady hole-boring is given theoretically and verified numerically by particle-in-cell simulations. Furthermore, we propose to achieve fast ignition by the in-situ hole-boring accelerated ions using a tailored laser pulse. Simulations show that the effectivemore » energy fluence, conversion efficiency, energy spread, and collimation of the resulting ion beam can be significantly improved as compared to those found with un-tailored laser profiles. For the fusion fuel with an areal density of 1.5 g cm{sup –2}, simulation indicates that it is promising to realize fast ion ignition by using a tailored driver pulse with energy about 65 kJ.« less

Maintaining stable radiation pressure acceleration of ion beams via cascaded electron replenishment

NASA Astrophysics Data System (ADS)

Shen, X. F.; Qiao, B.; Chang, H. X.; Zhang, W. L.; Zhang, H.; Zhou, C. T.; He, X. T.

2017-03-01

A method to maintain ion stable radiation pressure acceleration (RPA) from laser-irradiated thin foils is proposed, where a series of high-Z nanofilms are placed behind to successively replenish co-moving electrons into the accelerating foil as electron charging stations (ECSs). Such replenishment of co-moving electrons, on the one hand, helps to keep a dynamic balance between the electrostatic pressure in the accelerating slab and the increasing laser radiation pressure with a Gaussian temporal profile at the rising front, i.e. dynamically matching the optimal condition of RPA; on the other hand, it aids in suppressing the foil Coulomb explosion due to loss of electrons induced by transverse instabilities during RPA. Two-dimensional and three-dimensional particle-in-cell simulations show that a monoenergetic Si14+ beam with a peak energy of 3.7 GeV and particle number 4.8× {10}9 (charge 11 nC) can be obtained at an intensity of 7 × 1021 W cm-2 and the conversion efficiency from laser to high energy ions is improved significantly by using the ECSs in our scheme.

Highly coherent vacuum ultraviolet radiation at the 15th harmonic with echo-enabled harmonic generation technique

NASA Astrophysics Data System (ADS)

Hemsing, E.; Dunning, M.; Hast, C.; Raubenheimer, T. O.; Weathersby, S.; Xiang, D.

2014-07-01

X-ray free-electron lasers are enabling access to new science by producing ultrafast and intense x rays that give researchers unparalleled power and precision in examining the fundamental nature of matter. In the quest for fully coherent x rays, the echo-enabled harmonic generation technique is one of the most promising methods. In this technique, coherent radiation at the high harmonic frequencies of two seed lasers is generated from the recoherence of electron beam phase space memory. Here we report on the generation of highly coherent and stable vacuum ultraviolet radiation at the 15th harmonic of an infrared seed laser with this technique. The experiment demonstrates two distinct advantages that are intrinsic to the highly nonlinear phase space gymnastics of echo-enabled harmonic generation in a new regime, i.e., high frequency up-conversion efficiency and insensitivity to electron beam phase space imperfections. Our results allow comparison and confirmation of predictive models and scaling laws, and mark a significant step towards fully coherent x-ray free-electron lasers that will open new scientific research.

SU-E-I-42: Measurement of X-Ray Beam Width and Geometric Efficiency in MDCT Using Radiochromic Films.

PubMed

Liillau, T; Liebmann, M; von Boetticher, H; Poppe, B

2012-06-01

The purpose of this work was to measure the x-ray beam width and geometric efficiency (GE) of a multi detector computed tomography scanner (MDCT) for different beam collimations using radiochromic films. In MDCT, the primary beam width extends the nominal beam collimation to irradiate the active detector elements uniformly (called 'over-beaming') which contributes to increased radiation dose to the patient compared to single detector CT. Therefore, the precise determination of the primary beam width and GE is of value for any CT dose calculation using Monte Carlo or analytical methods. Single axial dose profiles free in air were measured for 6 different beam collimations nT for a Siemens SOMATOM Sensation 64 Scanner with Gafchromic XR-QA2 films. The films were calibrated relative to the measured charge of a PTW semiflex ionization chamber (type: 31010) for a single rotation in the CT scanner at the largest available beam collimation of 28.8 mm. The beam energy for all measurements in this work was set to 120 kVp. For every measured dose profile and beam collimation the GEin-air and the full-width-at-half- maximum value (FWHM) as a value for the x-ray beam width was determined. Over-beaming factors FWHM / nT were calculated accordingly. For MDCT beam collimations from 7.2 (12×0.6 mm) to 28.8 (24×1.2 mm) the geometric efficiency was between 58 and 85 %. The over- beaming factor ranged from 1.43 to 1.11. For beam collimations of 1×5 mm and 1×10 mm the GE was 77 % and 84 % respectively. The over-beaming factors were close to 1, as expected. This work has shown that radiochromic films can be used for accurate x-ray beam width and geometric efficiency measurements due to their high spatial resolution. The measured free-in-air geometric efficiency and the over-beaming factor depend strongly on beam collimation. © 2012 American Association of Physicists in Medicine.

Near-IR, blue, and UV generation by frequency conversion of a Tm:YAP laser

NASA Astrophysics Data System (ADS)

Cole, Brian; Goldberg, Lew; Chinn, Steve

2018-02-01

We describe generation of near-infrared (944nm, 970nm), blue (472nm, 485nm), and UV (236 nm) light by frequency up-conversion of 2 μm output of a compact and efficient passively Q-switched Tm:YAP laser. The Tm:YAP laser source was near diffraction limited with maximum Q-switched pulse peak power of 190 kW. For second harmonic generation (SHG) of NIR, both periodically poled lithium niobate (PPLN) and lithium tri-borate (LBO) were evaluated, with 58% conversion efficiency and 3.1 W of 970 nm power achieved with PPLN. The PPLN 970nm emission was frequency doubled in 20mm long type I LBO, generating 1.1 W at 485nm with a conversion efficiency of 34%. With LBO used for frequency doubling of 2.3 W of 1888 nm Tm:YAP output to 944nm, 860mW was generated, with 37% conversion efficiency. Using a second LBO crystal to generate the 4th harmonic, 545mW of 472nm power was generated, corresponding to 64% conversion efficiency. To generate the 8th harmonic of Tm:YAP laser emission, the 472nm output of the second LBO was frequency doubled in a 7mm long BBO crystal, generating 110 mW at 236nm, corresponding to 21% conversion efficiency.

A Highly intense DC muon source, MuSIC and muon CLFV search

NASA Astrophysics Data System (ADS)

Hino, Y.; Kuno, Y.; Sato, A.; Sakamoto, H.; Matsumoto, Y.; Tran, N. H.; Hashim, I. H.; Fukuda, M.; Hayashida, Y.; Ogitsu, T.; Yamamoto, A.; Yoshida, M.

2014-08-01

MuSIC is a new muon facility, which provides the world's highest intense muon beam with continuous time structure at Research Center of Nuclear Physics (RCNP), Osaka University. It's intensity is designed to be 108 muons per second with only 0.4 kW proton beam. Such a high intense muon beam is very important for searches of rare decay processes, for example search for the muon to electron conversion.

Ion-recombination correction for different ionization chambers in high dose rate flattening-filter-free photon beams

NASA Astrophysics Data System (ADS)

Lang, Stephanie; Hrbacek, Jan; Leong, Aidan; Klöck, Stephan

2012-05-01

Recently, there has been an increased interest in flattening-filter-free (FFF) linear accelerators. Removal of the filter results in available dose rates up to 24 Gy min-1 (for nominal energy 10 MV in depth of maximum dose, a source-surface distance of 100 cm and a field size of 10×10 cm2). To guarantee accurate relative and reference dosimetry for the FFF beams, we investigated the charge collection efficiency of multiple air-vented and one liquid ionization chamber for dose rates up to 31.9 Gy min-1. For flattened beams, the ion-collection efficiency of all air-vented ionization chambers (except for the PinPoint chamber) was above 0.995. By removing the flattening filter, we found a reduction in collection efficiency of approximately 0.5-0.9% for a 10 MV beam. For FFF beams, the Markus chamber showed the largest collection efficiency of 0.994. The observed collection efficiencies were dependent on dose per pulse, but independent of the pulse repetition frequency. Using the liquid ionization chamber, the ion-collection efficiency for flattened beams was above 0.990 for all dose rates. However, this chamber showed a low collection efficiency of 0.940 for the FFF 10 MV beam at a dose rate of 31.9 Gy min-1. All investigated air-vented ionization chambers can be reliably used for relative dosimetry of FFF beams. The order of correction for reference dosimetry is given in the manuscript. Due to their increased saturation in high dose rate FFF beams, liquid ionization chambers appear to be unsuitable for dosimetry within these contexts.

Status of photoelectrochemical production of hydrogen and electrical energy

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Walker, G. H.

1976-01-01

The efficiency for conversion of electromagnetic energy to chemical and electrical energy utilizing semiconductor single crystals as photoanodes in electrochemical cells was investigated. Efficiencies as high as 20 percent were achieved for the conversion of 330 nm radiation to chemical energy in the form of hydrogen by the photoelectrolysis of water in a SrTiO3 based cell. The SrTiO3 photoanodes were shown to be stable in 9.5 M NaOH solutions for periods up to 48 hours. Efficiencies of 9 percent were measured for the conversion of broadband visible radiation to hydrogen using n-type GaAs crystals as photoanodes. Crystals of GaAs coated with 500 nm of gold, silver, or tin for surface passivation show no significant change in efficiency. By suppressing the production of hydrogen in a CdSe-based photogalvanic cell, an efficiency of 9 percent was obtained in conversion of 633 nm light to electrical energy. A CdS-based photogalvanic cell produced a conversion efficiency of 5 percent for 500 nm radiation.

Hierarchical Graphene Foam for Efficient Omnidirectional Solar-Thermal Energy Conversion.

PubMed

Ren, Huaying; Tang, Miao; Guan, Baolu; Wang, Kexin; Yang, Jiawei; Wang, Feifan; Wang, Mingzhan; Shan, Jingyuan; Chen, Zhaolong; Wei, Di; Peng, Hailin; Liu, Zhongfan

2017-10-01

Efficient solar-thermal energy conversion is essential for the harvesting and transformation of abundant solar energy, leading to the exploration and design of efficient solar-thermal materials. Carbon-based materials, especially graphene, have the advantages of broadband absorption and excellent photothermal properties, and hold promise for solar-thermal energy conversion. However, to date, graphene-based solar-thermal materials with superior omnidirectional light harvesting performances remain elusive. Herein, hierarchical graphene foam (h-G foam) with continuous porosity grown via plasma-enhanced chemical vapor deposition is reported, showing dramatic enhancement of broadband and omnidirectional absorption of sunlight, which thereby can enable a considerable elevation of temperature. Used as a heating material, the external solar-thermal energy conversion efficiency of the h-G foam impressively reaches up to ≈93.4%, and the solar-vapor conversion efficiency exceeds 90% for seawater desalination with high endurance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of electronegative additives on physical properties and chemical activity of gas discharge plasma

NASA Astrophysics Data System (ADS)

Kuznetsov, D. L.; Filatov, I. E.; Uvarin, V. V.

2018-01-01

Effect of electronegative additives (oxygen O2, sulfur dioxide SO2, carbon disulfide CS2, and carbon tetrachloride CCl4) on physical properties and chemical activity of plasma formed by pulsed corona discharge and by non-self-sustained discharge supported by pulsed electron beam in atmospheric pressure gas mixtures was investigated. It is shown that a decrease in discharge current depends on a sort of the additive and on its concentration. The reason is the difference in rate constants of electron attachment processes for the above molecules. In experiments on volatile organic compounds (VOCs) conversion in air by streamer corona it is obtained that an addition of CCl4 both decreases the discharge current amplitude and increases the VOCs conversion degree. An installation for investigation of electron attachment processes and for study of toxic impurities conversion in plasma formed by non-self-sustained discharge initiated by pulsed nanosecond electron beam is created.

Method of achieving ultra-wideband true-time-delay beam steering for active electronically scanned arrays

DOEpatents

Loui, Hung; Brock, Billy C.

2016-10-25

The various embodiments presented herein relate to beam steering an array antenna by modifying intermediate frequency (IF) waveforms prior to conversion to RF signals. For each channel, a direct digital synthesis (DDS) component can be utilized to generate a waveform or modify amplitude, timing and phase of a waveform relative to another waveform, whereby the generation/modification can be performed prior to the IF input port of a mixer on each channel. A local oscillator (LO) signal can be utilized to commonly drive each of the mixers. After conversion at the RF output port of each of the mixers, each RF signal can be transmitted by a respective antenna element in the antenna array. Initiation of transmission of each RF signal can be performed simultaneously at each antenna. The process can be reversed during receive whereby timing, amplitude, and phase of the received can be modified digitally post ADC conversion.

Satellite analog FDMA/FM to digital TDMA conversion

NASA Technical Reports Server (NTRS)

Driggers, T.; Nguyen, T.; Kolavennu, V.

1987-01-01

The results of a study which investigated design issues regarding the use of analog to digital (A/D) conversion on board a satellite are presented. The need for A/D, and of course D/A as well, conversion arose from a satellite design which required analog FDMA/FM up and down links to/from a digitally modulated intersatellite link. There are also some advantages when one must interconnect a large number of various spot beams which are using analog, and therefore cannot take advantage of SS/TDMA switching among the beams, thus resulting in low fill factors. Various tradeoffs were performed regarding the implementation of on-board A/D processing, including mass, power, and costs. The various technologies which were considered included flash ADCs, surface acoustic wave (SAW) devices, and digital signal processing (DSP) chips. Impact analyses were also performed to determine the effect on ground stations to convert to digital if the A/D approach were not implemented.

Spatial two-photon coherence of the entangled field produced by down-conversion using a partially spatially coherent pump beam

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

Jha, Anand Kumar; Boyd, Robert W.

2010-01-15

We study the spatial coherence properties of the entangled two-photon field produced by parametric down-conversion (PDC) when the pump field is, spatially, a partially coherent beam. By explicitly treating the case of a pump beam of the Gaussian Schell-model type, we show that in PDC the spatial coherence properties of the pump field get entirely transferred to the spatial coherence properties of the down-converted two-photon field. As one important consequence of this study, we find that, for two-qubit states based on the position correlations of the two-photon field, the maximum achievable entanglement, as quantified by concurrence, is bounded by themore » degree of spatial coherence of the pump field. These results could be important by providing a means of controlling the entanglement of down-converted photons by tailoring the degree of coherence of the pump field.« less

Self-Inversion of the Image of a Small-Scale Opaque Object in the Process of Focusing of the Illuminating Beam in an Absorbing Medium

NASA Astrophysics Data System (ADS)

Bubis, E. L.; Lozhrkarev, V. V.; Stepanov, A. N.; Smirnov, A. I.; Martynov, V. O.; Mal'shakova, O. A.; Silin, D. E.; Gusev, S. A.

2017-03-01

We describe the process of adaptive self-inversion of an image (nonlinear switching) of smallscale opaque object, when the amplitude-modulated laser beam, which illuminates it, is focused in a weakly absorbing medium. It is shown that, despite the nonlocal character of the process, which is due to thermal nonlinearity, the brightness-inverse image is characterized by acceptable quality and a high conversion coefficient. It is shown that the coefficient of conversion of the original image to the inverse one depends on the ratio of the object dimensions and the size of the illuminating beam, and decreases sharply for relatively large objects. The obtained experimental data agree with the numerical calculations. Inversion of the images of several model objects and microdefects in a nonlinear KDP crystal is demonstrated.

Single crystal CVD diamond membranes for betavoltaic cells

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

Delfaure, C.; Pomorski, M., E-mail: michal.pomorski@cea.fr; Sanoit, J. de

2016-06-20

A single crystal diamond large area thin membrane was assembled as a p-doped/Intrinsic/Metal (PIM) structure and used in a betavoltaic configuration. When tested with a 20 keV electron beam from a high resolution scanning electron microscope, we measured an open circuit voltage (V{sub oc}) of 1.85 V, a charge collection efficiency (CCE) of 98%, a fill-factor of 80%, and a total conversion efficiency of 9.4%. These parameters are inherently linked to the diamond membrane PIM structure that allows full device depletion even at 0 V and are among the highest reported up to now for any other material tested for betavoltaic devices. Itmore » enables to drive a high short-circuit current I{sub sc} up to 7.12 μA, to reach a maximum power P{sub max} of 10.48 μW, a remarkable value demonstrating the high-benefit of diamond for the realization of long-life radioisotope based micro-batteries.« less

Mode competition and selection in overmoded surface wave oscillator

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

Wang, Guangqiang; Zeng, Peng; Wang, Dongyang

2016-05-15

The overmoded surface wave oscillator (SWO) is one of the promising devices to generate high-power millimeter and subterahertz waves for its merits of high efficiency and easy fabrication. But the employed slow wave structure with large diameter may introduce mode competition as the adverse effects. Therefore, the mode competition and selection in the overmoded surface wave oscillator are investigated in detail in this paper. By using the theoretical analysis and particle-in-cell simulation, the potential transverse mode and axial mode competition is pointed out, and the physical mechanisms and methods for mode selection are investigated. At last, the results are verifiedmore » in the design of a 0.14 THz overmoded SWO without mode competition, which can generate the output power up to 70 MW at the frequency of 146.3 GHz with conversion efficiency almost 20% when beam voltage and current are, respectively, about 313 kV and 1.13 kA.« less

Effect of the Molecular Nature of Mutation on the Efficiency of Intrachromosomal Gene Conversion in Mouse Cells

PubMed Central

Letsou, Anthea; Liskay, R. Michael

1987-01-01

With the intent of further exploring the nature of gene conversion in mammalian cells, we systematically addressed the effects of the molecular nature of mutation on the efficiency of intrachromosomal gene conversion in cultured mouse cells. Comparison of conversion rates revealed that all mutations studied were suitable substrates for gene conversion; however, we observed that the rates at which different mutations converted to wild-type could differ by two orders of magnitude. Differences in conversion rates were correlated with the molecular nature of the mutations. In general, rates of conversion decreased with increasing size of the molecular lesions. In comparisons of conversion rates for single base pair insertions and deletions we detected a genotype-directed path for conversion, by which an insertion was converted to wild-type three to four times more efficiently than was a deletion which maps to the same site. The data are discussed in relation to current theories of gene conversion, and are consistent with the idea that gene conversion in mammalian cells can result from repair of heteroduplex DNA (hDNA) intermediates. PMID:2828159

Thermodynamic limit for coherence-limited solar power conversion

NASA Astrophysics Data System (ADS)

Mashaal, Heylal; Gordon, Jeffrey M.

2014-09-01

The spatial coherence of solar beam radiation is a key constraint in solar rectenna conversion. Here, we present a derivation of the thermodynamic limit for coherence-limited solar power conversion - an expansion of Landsberg's elegant basic bound, originally limited to incoherent converters at maximum flux concentration. First, we generalize Landsberg's work to arbitrary concentration and angular confinement. Then we derive how the values are further lowered for coherence-limited converters. The results do not depend on a particular conversion strategy. As such, they pertain to systems that span geometric to physical optics, as well as classical to quantum physics. Our findings indicate promising potential for solar rectenna conversion.

Feasibility of Colliding-beam fast-fission reactor via 238U80++238 U80+ --> 4 FF + 5n + 430 MeV beam with suppressed plutonium and direct conversion of fission fragment (FF) energy into electricity and/or Rocket propellant with high specific impulse

NASA Astrophysics Data System (ADS)

Maglich, Bogdan; Hester, Tim; Calsec Collaboration

2015-10-01

Uranium-uranium colliding beam experiment1, used fully ionized 238U92+ at energy 100GeV --> <-- 100 GeV, has measured total σ = 487 b. Reaction rate of colliding beams is proportional to neutron flux-squared. First functional Auto-Collider3-6, a compact Migma IV, 1 m in diameter, had self-colliding deuterons, D+, of 725 KeV --> <-- 725 KeV, resulting in copious production of T and 3He. U +U Autocollider``EXYDER'' will use strong-focusing magnet7, which would increase reaction rate by 104. 80 times ionized U ions accelerated through 3 MV accelerator, will collide beam 240 MeV --> <-- 240 MeV. Reaction is: 238U80+ +238 U80+ --> 4 FF + 5n + 430 MeV. Using a simple model1 fission σf ~ 100 b. Suppression of Pu by a factor of 106 will be achieved because NO thermal neutron fission can take place; only fast, 1-3 MeV, where σabs is negligible. Direct conversion of 95% of 430 MeV produced is carried by electrically charged FFs which are magnetically funneled for direct conversion of energy of FFs via electrostatic decelerators4,11. 90% of 930 MeV is electrically recoverable. Depending on the assumptions, we project electric _ power density production of 20 to 200 MWe m-3, equivalent to Thermal 1.3 - 13 GWthm-3. If one-half of unburned U is used for propulsion while rest powers system, heavy FF ion mass provides specific impulse Isp = 106 sec., 103 times higher than current rocket engines.

High-power continuous-wave tunable 544- and 272-nm beams based on a diode-oscillator fiber-amplifier for calcium spectroscopy

NASA Astrophysics Data System (ADS)

Ko, Kwang-Hoon; Kim, Yonghee; Park, Hyunmin; Cha, Yong-Ho; Kim, Taek-Soo; Lee, Lim; Lim, Gwon; Han, Jaemin; Ko, Kwang-Hee; Jeong, Do-Young

2015-08-01

Continuous-wave single-frequency tunable 544- and 272-nm beams have been demonstrated by the second- and fourth-harmonic conversions of a 1088-nm fundamental beam from a diode-oscillator fiber-amplifier. The single-pass second-harmonic generation with a MgO-doped periodically poled stoichiometric LiTaO3 crystal and the external-cavity frequency-doubling technique with a bulk BBO crystal were employed to achieve an approximately 6-W 544-nm beam and a 1.5-W 272-nm beam, respectively. We characterized the second- and fourth-harmonic generations and discussed their applications to calcium spectroscopy.

Alternative Beam Efficiency Calculations for a Large-aperture Multiple-frequency Microwave Radiometer (LAMMR)

NASA Technical Reports Server (NTRS)

Schmidt, R. F.

1979-01-01

The fundamental definition of beam efficiency, given in terms of a far field radiation pattern, was used to develop alternative definitions which improve accuracy, reduce the amount of calculation required, and isolate the separate factors composing beam efficiency. Well-known definitions of aperture efficiency were introduced successively to simplify the denominator of the fundamental definition. The superposition of complex vector spillover and backscattered fields was examined, and beam efficiency analysis in terms of power patterns was carried out. An extension from single to dual reflector geometries was included. It is noted that the alternative definitions are advantageous in the mathematical simulation of a radiometer system, and are not intended for the measurements discipline where fields have merged and therefore lost their identity.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells.

PubMed

Sahin, Mehmet

2018-05-23

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p-n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy ([Formula: see text]) of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same [Formula: see text]. The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same [Formula: see text], become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

Second NASA Conference on Laser Energy Conversion

NASA Technical Reports Server (NTRS)

Billman, K. W. (Editor)

1976-01-01

The possible transmission of high power laser beams over long distances and their conversion to thrust, electricity, or other useful forms of energy is considered. Specific topics discussed include: laser induced chemistry; developments in photovoltaics, including modification of the Schottky barrier devices and generation of high voltage emf'sby laser radiation of piezoelectric ceramics; the thermo electronic laser energy converter and the laser plasmadynamics converters; harmonic conversion of infrared laser radiation in molecular gases; and photon engines.

Compact x-ray source and panel

DOEpatents

Sampayon, Stephen E [Manteca, CA

2008-02-12

A compact, self-contained x-ray source, and a compact x-ray source panel having a plurality of such x-ray sources arranged in a preferably broad-area pixelized array. Each x-ray source includes an electron source for producing an electron beam, an x-ray conversion target, and a multilayer insulator separating the electron source and the x-ray conversion target from each other. The multi-layer insulator preferably has a cylindrical configuration with a plurality of alternating insulator and conductor layers surrounding an acceleration channel leading from the electron source to the x-ray conversion target. A power source is connected to each x-ray source of the array to produce an accelerating gradient between the electron source and x-ray conversion target in any one or more of the x-ray sources independent of other x-ray sources in the array, so as to accelerate an electron beam towards the x-ray conversion target. The multilayer insulator enables relatively short separation distances between the electron source and the x-ray conversion target so that a thin panel is possible for compactness. This is due to the ability of the plurality of alternating insulator and conductor layers of the multilayer insulators to resist surface flashover when sufficiently high acceleration energies necessary for x-ray generation are supplied by the power source to the x-ray sources.

Enhancement of the efficiency of dye-sensitized solar cell with multi-wall carbon nanotubes/polypyrrole composite counter electrodes prepared by electrophoresis/electrochemical polymerization

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

Luo, Jun; Niu, Hai-jun; Wen, Hai-lin

2013-03-15

Graphical abstract: The overall energy conversion efficiency of the DSSC employing the MWCNT/PPy CE reached 3.78%. Compared with a reference DSSC using single MWCNT film CE with efficiency of 2.68%, the energy conversion efficiency was increased by 41.04%. Highlights: ► MWCNT/PPy composite film prepared by electrodeposition layer by layer was used as counter electrode in DSSC. ► The overall energy conversion efficiency of the DSSC was 3.78% by employing the composite film. ► The energy conversion efficiency increased by 41.04% compared with efficiency of 2.68% by using the single MWCNT film. ► We analyzed the mechanism and influence factor ofmore » electron transfer in the composite electrode by EIS. - Abstract: For the purpose of replacing the precious Pt counter electrode in dye-sensitized solar cells (DSSCs) with higher energy conversion efficiency, multi-wall carbon nanotube (MWCNT)/polypyrrole (PPy) double layers film counter electrode (CE) was fabricated by electrophoresis and cyclic voltammetry (CV) layer by layer. Atom force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscope (TEM) demonstrated the morphologies of the composite electrode and Raman spectroscopy verified the PPy had come into being. The overall energy conversion efficiency of the DSSC employing the MWCNT/PPy CE reached 3.78%. Compared with a reference DSSC using single MWCNT film CE with efficiency of 2.68%, the energy conversion efficiency was increased by 41.04%. The result of impedance showed that the charge transfer resistance R{sub ct} of the MWCNT/PPy CE had the lowest value compared to that of MWCNT or PPy electrode. These results indicate that the composite film with high conductivity, high active surface area, and good catalytic properties for I{sub 3}{sup −} reduction can potentially be used as the CE in a high-performance DSSC.« less

Efficiency of Energy Harvesting in Ni-Mn-Ga Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Lindquist, Paul; Hobza, Tony; Patrick, Charles; Müllner, Peter

2018-03-01

Many researchers have reported on the voltage and power generated while energy harvesting using Ni-Mn-Ga shape memory alloys; few researchers report on the power conversion efficiency of energy harvesting. We measured the magneto-mechanical behavior and energy harvesting of Ni-Mn-Ga shape memory alloys to quantify the efficiency of energy harvesting using the inverse magneto-plastic effect. At low frequencies, less than 150 Hz, the power conversion efficiency is less than 0.1%. Power conversion efficiency increases with (i) increasing actuation frequency, (ii) increasing actuation stroke, and (iii) decreasing twinning stress. Extrapolating the results of low-frequency experiments to the kHz actuation regime yields a power conversion factor of about 20% for 3 kHz actuation frequency, 7% actuation strain, and 0.05 MPa twinning stress.

Experimental feasibility of the airborne measurement of absolute oil fluorescence spectral conversion efficiency

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1983-01-01

Airborne lidar oil spill experiments carried out to determine the practicability of the AOFSCE (absolute oil fluorescence spectral conversion efficiency) computational model are described. The results reveal that the model is suitable over a considerable range of oil film thicknesses provided the fluorescence efficiency of the oil does not approach the minimum detection sensitivity limitations of the lidar system. Separate airborne lidar experiments to demonstrate measurement of the water column Raman conversion efficiency are also conducted to ascertain the ultimate feasibility of converting such relative oil fluorescence to absolute values. Whereas the AOFSCE model is seen as highly promising, further airborne water column Raman conversion efficiency experiments with improved temporal or depth-resolved waveform calibration and software deconvolution techniques are thought necessary for a final determination of suitability.

Methods and devices based on brillouin selective sideband amplification

NASA Technical Reports Server (NTRS)

Yao, X. Steve (Inventor)

2003-01-01

Opto-electronic devices and techniques using Brillouin scattering to select a sideband in a modulated optical carrier signal for amplification. Two lasers respectively provide a carrier signal beam and a Brillouin pump beam which are fed into an Brillouin optical medium in opposite directions. The relative frequency separation between the lasers is adjusted to align the frequency of the backscattered Brillouin signal with a desired sideband in the carrier signal to effect a Brillouin gain on the sideband. This effect can be used to implement photonic RF signal mixing and conversion with gain, conversion from phase modulation to amplitude modulation, photonic RF frequency multiplication, optical and RF pulse generation and manipulation, and frequency-locking of lasers.

Conversion coefficients for determining organ doses in paediatric spine radiography.

PubMed

Seidenbusch, Michael; Schneider, Karl

2014-04-01

Knowledge of organ and effective doses achieved during paediatric x-ray examinations is an important prerequisite for assessment of radiation burden to the patient. Conversion coefficients for reconstruction of organ and effective doses from entrance doses for segmental spine radiographs of 0-, 1-, 5-, 10-, 15- and 30-year-old patients are provided regarding the Guidelines of Good Radiographic Technique of the European Commission. Using the personal computer program PCXMC developed by the Finnish Centre for Radiation and Nuclear Safety (Säteilyturvakeskus STUK), conversion coefficients for conventional segmental spine radiographs were calculated performing Monte Carlo simulations in mathematical hermaphrodite phantom models describing patients of different ages. The clinical variation of beam collimation was taken into consideration by defining optimal and suboptimal radiation field settings. Conversion coefficients for the reconstruction of organ doses in about 40 organs and tissues from measured entrance doses during cervical, thoracic and lumbar spine radiographs of 0-, 1-, 5-, 10-, 15- and 30-year-old patients were calculated for the standard sagittal and lateral beam projections and the standard focus detector distance of 115 cm. The conversion coefficients presented may be used for organ dose assessments from entrance doses measured during spine radiographs of patients of all age groups and all field settings within the optimal and suboptimal standard field settings.

Structured light generation by magnetic metamaterial half-wave plates at visible wavelength

NASA Astrophysics Data System (ADS)

Zeng, Jinwei; Luk, Ting S.; Gao, Jie; Yang, Xiaodong

2017-12-01

Metamaterial or metasurface unit cells functioning as half-wave plates play an essential role for realizing ideal Pancharatnam-Berry phase optical elements capable of tailoring light phase and polarization as desired. Complex light beam manipulation through these metamaterials or metasurfaces unveils new dimensions of light-matter interactions for many advances in diffraction engineering, beam shaping, structuring light, and holography. However, the realization of metamaterial or metasurface half-wave plates in visible spectrum range is still challenging mainly due to its specific requirements of strong phase anisotropy with amplitude isotropy in subwavelength scale. Here, we propose magnetic metamaterial structures which can simultaneously exploit the electric field and magnetic field of light for achieving the nanoscale half-wave plates at visible wavelength. We design and demonstrate the magnetic metamaterial half-wave plates in linear grating patterns with high polarization conversion purity in a deep subwavelength thickness. Then, we characterize the equivalent magnetic metamaterial half-wave plates in cylindrical coordinate as concentric-ring grating patterns, which act like an azimuthal half-wave plate and accordingly exhibit spatially inhomogeneous polarization and phase manipulations including spin-to-orbital angular momentum conversion and vector beam generation. Our results show potentials for realizing on-chip beam converters, compact holograms, and many other metamaterial devices for structured light beam generation, polarization control, and wavefront manipulation.

Interplanetary particle beams

NASA Technical Reports Server (NTRS)

Dulk, G. A.

1990-01-01

This paper reviews observations of interplanetary particle beams of the kind that frequently accompany a solar flare. It is shown that the most frequently observed beams are beams of electrons which are associated with radio bursts of type III, but occasionally with flares and X-ray bursts. Although the main features of these beams and their associated plasma waves and radio bursts are known, uncertainties remain in terms of the correlation between electron beams and filamentary structures, the relative importance of the quasi-linear and the nonlinear wave emissions as the dominant process, and the mechanism of conversion of some of the Langmuir wave energy into radio emissions. Other particle beams discussed are those composed of protons, neutrons, He ions, or heavy ions. While most of these beams originate from sun flares, the source of some of particle beams may be the earth, Jupiter, or other planets as well as comets.

Combining module based on coherent polarization beam combining.

PubMed

Yang, Yan; Geng, Chao; Li, Feng; Li, Xinyang

2017-03-01

A multiaperture receiver with a phased array is an effective approach to overcome the effect of the random optical disturbance in coherent free-space laser communications, in which one of the key technologies is how to efficiently combine the multiple laser beams received by the phased array antenna. A combining module based on coherent polarization beam combining (CPBC), which can combine multiple laser beams to one laser beam with high combining efficiency and output a linearly polarized beam, is proposed in this paper. The principle of the combining module is introduced, the coherent polarization combining efficiency of CPBC is analyzed, and the performance of the combining module is evaluated. Moreover, the feasibility and the expansibility of the proposed combining module are validated in experiments of CPBC based on active phase-locking.

Experimental Investigation of the Strength of Multiweb Beams with Corrugated Webs

NASA Technical Reports Server (NTRS)

Fraser, Allister F

1956-01-01

The results of an experimental investigation of the strength of multiweb beams with corrugated webs are reported. Included in the investigation were two types of connection between the web and the skin. A comparison between the structural efficiency of corrugated-web and channel-web multiweb beams is presented, and it is shown that, for a considerable range of the structural index, corrugated-web beams can be built which are structurally more efficient than channel-web beams.

Latest developments on fibered MOPA in mJ range with hollow-core fiber beam delivery and fiber beam shaping used as seeder for large scale laser facilities (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gleyze, Jean-François; Scol, Florent; Perrin, Arnaud; Gouriou, Pierre; Valentin, Constance; Bouwmans, Géraud; Hugonnot, Emmanuel

2017-05-01

The Laser Megajoule (LMJ) is a French large scale laser facility dedicated to inertial fusion and plasma physics research. LMJ front-ends are based on fiber laser technology at nanojoule range [1]. Scaling the energy of those fiber seeders to the millijoule range is a way to upgrade LMJ's front ends architecture and could also be used as seeder for lasers for ELI project for example. However, required performances are so restrictive (optical-signal-to-noise ratio higher than 50 dB, temporally-shaped nanosecond pulses and spatial single-mode top-hat beam output) that such fiber systems are very tricky to build. High-energy fiber amplifiers In 2015, we have demonstrated, an all-fiber MOPA prototype able to produce a millijoule seeder, but unfortunately not 100% conform for all LMJ's performances. A major difficulty was to manage the frequency modulation used to avoid stimulated Brillouin scattering, to amplitude modulation (FM-AM) conversion, this limits the energy at 170µJ. For upgrading the energy to the millijoule range, it's necessary to use an amplifier with a larger core fiber. However, this fiber must still be flexible; polarization maintaining and exhibit a strictly single-mode behaviour. We are thus developing a new amplifier architecture based on an Yb-doped tapered fiber: its core diameter is from a narrow input to a wide output (MFD 8 to 26 µm). A S² measurement on a 2,5m long tapered fiber rolled-up on 22 cm diameter confirmed that this original geometry allows obtaining strictly single-mode behaviour. In a 1 kHz repetition rate regime, we already obtain 750 µJ pulses, and we are on the way to mJ, respecting LMJ performances. Beam delivery In LMJ architecture the distance between the nanojoule fiber seeder and the amplifier stages is about 16 m. Beam delivery is achieved with a standard PM fiber, such a solution is no longer achievable with hundreds of kilowatt peak powers. An efficient way to minimize nonlinear effects is to use hollow-core (HC) fibers. The comparison between the different fibers will be presented in the conference. Fiber spatial beam shaping Spatial beam shaping (top-hat profile) is mandatory to optimize the energy extraction in free-space amplifier. It would be very interesting to obtain a flat-top beam in an all-fiber way. Accordingly, we have design and realize a large mode area single-mode top-hat fiber able to deliver a coherent top-hat beam. This fiber, with larger MFD adapted to mJ pulse, will be implemented to perform the spatial beam shaping from coherent Gaussian profile to coherent top-hat intensity profile in the mJ range. In conclusion, we will present an all-fiber MOPA built to fulfil stringent requirements for large scale laser facility seeding. We have already achieved 750 µJ with 10 ns square pulses. Transport of high peak power pulses over 17 m in a hollow-core fiber has been achieved and points out FM to AM conversion management issues. Moreover, spatial beam shaping is obtained by using specifically designed single-mode fibers. Various optimizations are currently under progress and will be presented.

Development of gas pulsing system for electron cyclotron resonance ion source.

PubMed

Hojo, S; Honma, T; Muramatsu, M; Sakamoto, Y; Sugiura, A

2008-02-01

A gas-pulsing system for an electron cyclotron resonance ion source with all permanent magnets (Kei2 source) at NIRS has been developed and tested. The system consists of a small vessel (30 ml) to reserve CH(4) gas and two fast solenoid valves that are installed at both sides of the vessel. They are connected to each other and to the Kei2 source by using a stainless-steel pipe (4 mm inner diameter), where the length of the pipe from the valve to the source is 60 cm and the conductance is 1.2 l/s. From the results of the test, almost 300 e microA for a pulsed (12)C(4+) beam was obtained at a Faraday cup in an extraction-beam channel with a pressure range of 4000 Pa in the vessel. At this time, the valve has an open time of 10 ms and the delay time between the valve open time and the application of microwave power is 100 ms. In experiments, the conversion efficiency for input CH(4) molecules to the quantity of extracted (12)C(4+) ions in one beam pulse was found to be around 3% and the ratio of the total amount of the gas requirement was only 10% compared with the case of continuous gas provided in 3.3 s of repetition in HIMAC.

High-performance multiple-reflection time-of-flight mass spectrometers for research with exotic nuclei and for analytical mass spectrometry

NASA Astrophysics Data System (ADS)

Plaß, Wolfgang R.; Dickel, Timo; Ayet San Andres, Samuel; Ebert, Jens; Greiner, Florian; Hornung, Christine; Jesch, Christian; Lang, Johannes; Lippert, Wayne; Majoros, Tamas; Short, Devin; Geissel, Hans; Haettner, Emma; Reiter, Moritz P.; Rink, Ann-Kathrin; Scheidenberger, Christoph; Yavor, Mikhail I.

2015-11-01

A class of multiple-reflection time-of-flight mass spectrometers (MR-TOF-MSs) has been developed for research with exotic nuclei at present and future accelerator facilities such as GSI and FAIR (Darmstadt), and TRIUMF (Vancouver). They can perform highly accurate mass measurements of exotic nuclei, serve as high-resolution, high-capacity mass separators and be employed as diagnostics devices to monitor the production, separation and manipulation of beams of exotic nuclei. In addition, a mobile high-resolution MR-TOF-MS has been developed for in situ applications in analytical mass spectrometry ranging from environmental research to medicine. Recently, the MR-TOF-MS for GSI and FAIR has been further developed. A novel RF quadrupole-based ion beam switchyard has been developed that allows merging and splitting of ion beams as well as transport of ions into different directions. It efficiently connects a test and reference ion source and an auxiliary detector to the system. Due to an increase in the kinetic energy of the ions in the time-of-flight analyzer of the MR-TOF-MS, a given mass resolving power is now achieved in less than half the time-of-flight. Conversely, depending on the time-of-flight, the mass resolving power has been increased by a factor of more than two.

Highly-efficient enzymatic conversion of crude algal oils into biodiesel.

PubMed

Wang, Yao; Liu, Jin; Gerken, Henri; Zhang, Chengwu; Hu, Qiang; Li, Yantao

2014-11-01

Energy-intensive chemical conversion of crude algal oils into biodiesel is a major barrier for cost-effective algal biofuel production. To overcome this problem, we developed an enzyme-based platform for conversion of crude algal oils into fatty acid methyl esters. Crude algal oils were extracted from the oleaginous microalga Nannochloropsis oceanica IMET1 and converted by an immobilized lipase from Candida antarctica. The effects of different acyl acceptors, t-butanol as a co-solvent, oil to t-butanol ratio, oil to methanol ratio, temperature and reaction time on biodiesel conversion efficiency were studied. The conversion efficiency reached 99.1% when the conversion conditions were optimized, i.e., an oil to t-butanol weight ratio of 1:1, an oil to methanol molar ratio of 1:12, and a reaction time of 4h at 25°C. The enzymatic conversion process developed in this study may hold a promise for low energy consumption, low wastewater-discharge biochemical conversion of algal feedstocks into biofuels. Published by Elsevier Ltd.

Progress Towards the Development of a Traveling Wave Direct Energy Converter for Aneutronic Fusion Propulsion Applications

NASA Technical Reports Server (NTRS)

Tarditi, A. G.; Chap, A.; Wolinsky, J.; Scott, J. H.

2015-01-01

A coordinated experimental and theory/simulation effort has been carried out to investigate the physics of the Traveling Wave Direct Energy Converter (TWDEC), a scheme that has been proposed in the past for the direct conversion into electricity of the kinetic energy of an ion beam generated from fusion reactions. This effort has been focused in particular on the TWDEC process in the high density beam regime, thus accounting for the ion beam expansion due to its space charge.

Double passing the Kitt Peak 1-m Fourier transform spectrometer

NASA Technical Reports Server (NTRS)

Jennings, D. E.; Hubbard, R.; Brault, J. W.

1985-01-01

Attention is given to a simple technique for performing the conversion of the Kitt Peak 1-m Fourier transform spectrometer's dual input/output optical configuration to a double pass configuration that improves spectral resolution by a factor of 2. The modification is made by placing a flat mirror in the output beam from each cat's eye, retroreflecting the beams back through the cat's eyes to the first beam splitter. A single detector is placed at the second input port, which then becomes the instrument's output.

Ionoluminescence properties of polystyrene-hosted fluorophore films induced by helium ions of energy 50-350 keV

NASA Astrophysics Data System (ADS)

Chakraborty, Subha; Huang, Mengbing

2017-10-01

We report on measurements and analysis of ionoluminescence properties of pure polystyrene films and polystyrene films doped with four types of fluorophores in low kinetic energies (50-350 keV) of ion irradiation. We have developed a theoretical model to understand the experimentally observed ionoluminescence behaviors in terms of scintillation yield from individual ion tracks, photophysical energy transfer mechanisms, and irradiation-induced defects. A comparison of the model and experimental results suggests that singlet up-conversion resulting from triplet-triplet annihilation processes may be responsible for enhanced singlet emission of the fluorophores at high ion beam flux densities. Energy transfer from the polystyrene matrix to the fluorophore molecules has been identified as an effective pathway to increasing the fluorescence efficiency in the doped scintillator films.

Characteristic analysis of a polarization output coupling Porro prism resonator

NASA Astrophysics Data System (ADS)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-02-01

An Electro-optical Q-switched Nd:YAG slab laser with a crossed misalignment Porro prism resonator for space applications has been theoretically and experimentally investigated. The phase shift induced by the combination of different wave plates and Porro prism azimuth angles have been studied for creating high loss condition prior to Q-switching. The relationship of the effective output coupling reflectivity and the employed Q-switch driving voltage is explored by using Jones matrix optics. In the experiment, the maximum output pulse energy of 93 mJ with 14-ns pulse duration is obtained at the repetition rate of 20 Hz and the optical-to-optical conversion efficiency is 16.8%. The beam quality factors are M 2 x = 2.5 and M 2y = 2.2, respectively.

Vibration reduction for smart periodic structures via periodic piezoelectric arrays with nonlinear interleaved-switched electronic networks

NASA Astrophysics Data System (ADS)

Bao, Bin; Guyomar, Daniel; Lallart, Mickaël

2017-01-01

Smart periodic structures covered by periodically distributed piezoelectric patches have drawn more and more attention in recent years for wave propagation attenuation and corresponding structural vibration suppression. Since piezoelectric materials are special type of energy conversion materials that link mechanical characteristics with electrical characteristics, shunt circuits coupled with such materials play a key role in the wave propagation and/or vibration control performance in smart periodic structures. Conventional shunt circuit designs utilize resistive shunt (R-shunt) and resonant shunt (RL-shunt). More recently, semi-passive nonlinear approaches have also been developed for efficiently controlling the vibrations of such structures. In this paper, an innovative smart periodic beam structure with nonlinear interleaved-switched electric networks based on synchronized switching damping on inductor (SSDI) is proposed and investigated for vibration reduction and wave propagation attenuation. Different from locally resonant band gap mechanism forming narrow band gaps around the desired resonant frequencies, the proposed interleaved electrical networks can induce new broadly low-frequency stop bands and broaden primitive Bragg stop bands by virtue of unique interleaved electrical configurations and the SSDI technique which has the unique feature of realizing automatic impedance adaptation with a small inductance. Finite element modeling of a Timoshenko electromechanical beam structure is also presented for validating dispersion properties of the structure. Both theoretical and experimental results demonstrate that the proposed beam structure not only shows better vibration and wave propagation attenuation than the smart beam structure with independent switched networks, but also has technical simplicity of requiring only half of the number of switches than the independent switched network needs.

Spatial Control of Photoemitted Electron Beams using a Micro-Lens-Array Transverse-Shaping Technique

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

Halavanau, A.; Qiang, G.; Ha, G.

2017-07-24

A common issue encountered in photoemission electron sources used in electron accelerators is the transverse inhomogeneity of the laser distribution resulting from the laser-amplification process and often use of frequency up conversion in nonlinear crystals. A inhomogeneous laser distribution on the photocathode produces charged beams with lower beam quality. In this paper, we explore the possible use of microlens arrays (fly-eye light condensers) to dramatically improve the transverse uniformity of the drive laser pulse on UV photocathodes. We also demonstrate the use of such microlens arrays to generate transversely-modulated electron beams and present a possible application to diagnose the propertiesmore » of a magnetized beam.« less

Interband Cascade Photovoltaic Cells

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

Yang, Rui Q.; Santos, Michael B.; Johnson, Matthew B.

2014-09-24

In this project, we are performing basic and applied research to systematically investigate our newly proposed interband cascade (IC) photovoltaic (PV) cells [1]. These cells follow from the great success of infrared IC lasers [2-3] that pioneered the use of quantum-engineered IC structures. This quantum-engineered approach will enable PV cells to efficiently convert infrared radiation from the sun or other heat source, to electricity. Such cells will have important applications for more efficient use of solar energy, waste-heat recovery, and power beaming in combination with mid-infrared lasers. The objectives of our investigations are to: achieve extensive understanding of the fundamentalmore » aspects of the proposed PV structures, develop the necessary knowledge for making such IC PV cells, and demonstrate prototype working PV cells. This research will focus on IC PV structures and their segments for utilizing infrared radiation with wavelengths from 2 to 5 μm, a range well suited for emission by heat sources (1,000-2,000 K) that are widely available from combustion systems. The long-term goal of this project is to push PV technology to longer wavelengths, allowing for relatively low-temperature thermal sources. Our investigations address material quality, electrical and optical properties, and their interplay for the different regions of an IC PV structure. The tasks involve: design, modeling and optimization of IC PV structures, molecular beam epitaxial growth of PV structures and relevant segments, material characterization, prototype device fabrication and testing. At the end of this program, we expect to generate new cutting-edge knowledge in the design and understanding of quantum-engineered semiconductor structures, and demonstrate the concepts for IC PV devices with high conversion efficiencies.« less

Maximum efficiency of state-space models of nanoscale energy conversion devices

NASA Astrophysics Data System (ADS)

Einax, Mario; Nitzan, Abraham

2016-07-01

The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

Maximum efficiency of state-space models of nanoscale energy conversion devices.

PubMed

Einax, Mario; Nitzan, Abraham

2016-07-07

The performance of nano-scale energy conversion devices is studied in the framework of state-space models where a device is described by a graph comprising states and transitions between them represented by nodes and links, respectively. Particular segments of this network represent input (driving) and output processes whose properly chosen flux ratio provides the energy conversion efficiency. Simple cyclical graphs yield Carnot efficiency for the maximum conversion yield. We give general proof that opening a link that separate between the two driving segments always leads to reduced efficiency. We illustrate these general result with simple models of a thermoelectric nanodevice and an organic photovoltaic cell. In the latter an intersecting link of the above type corresponds to non-radiative carriers recombination and the reduced maximum efficiency is manifested as a smaller open-circuit voltage.

10.2% power conversion efficiency polymer tandem solar cells consisting of two identical sub-cells.

PubMed

You, Jingbi; Chen, Chun-Chao; Hong, Ziruo; Yoshimura, Ken; Ohya, Kenichiro; Xu, Run; Ye, Shenglin; Gao, Jing; Li, Gang; Yang, Yang

2013-08-07

Polymer tandem solar cells with 10.2% power conversion efficiency are demonstrated via stacking two PDTP-DFBT:PC₇₁ BM bulk heterojunctions, connected by MoO₃/PEDOT:PSS/ZnO as an interconnecting layer. The tandem solar cells increase the power conversion efficiency of the PDTP-DFBT:PC₇₁ BM system from 8.1% to 10.2%, successfully demonstrating polymer tandem solar cells with identical sub-cells of double-digit efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conversion from dose-to-graphite to dose-to-water in an 80 MeV/A carbon ion beam.

PubMed

Rossomme, S; Palmans, H; Shipley, D; Thomas, R; Lee, N; Romano, F; Cirrone, P; Cuttone, G; Bertrand, D; Vynckier, S

2013-08-21

Based on experiments and numerical simulations, a study is carried out pertaining to the conversion of dose-to-graphite to dose-to-water in a carbon ion beam. This conversion is needed to establish graphite calorimeters as primary standards of absorbed dose in these beams. It is governed by the water-to-graphite mass collision stopping power ratio and fluence correction factors, which depend on the particle fluence distributions in each of the two media. The paper focuses on the experimental and numerical determination of this fluence correction factor for an 80 MeV/A carbon ion beam. Measurements have been performed in the nuclear physics laboratory INFN-LNS in Catania (Sicily, Italy). The numerical simulations have been made with a Geant4 Monte Carlo code through the GATE simulation platform. The experimental data are in good agreement with the simulated results for the fluence correction factors and are found to be close to unity. The experimental values increase with depth reaching 1.010 before the Bragg peak region. They have been determined with an uncertainty of 0.25%. Different numerical results are obtained depending on the level of approximation made in calculating the fluence correction factors. When considering carbon ions only, the difference between measured and calculated values is maximal just before the Bragg peak, but its value is less than 1.005. The numerical value is close to unity at the surface and increases to 1.005 near the Bragg peak. When the fluence of all charged particles is considered, the fluence correction factors are lower than unity at the surface and increase with depth up to 1.025 before the Bragg peak. Besides carbon ions, secondary particles created due to nuclear interactions have to be included in the analysis: boron ions ((10)B and (11)B), beryllium ions ((7)Be), alpha particles and protons. At the conclusion of this work, we have the conversion of dose-to-graphite to dose-to-water to apply to the response of a graphite calorimeter in an 80 MeV/A carbon ion beam. This conversion consists of the product of two contributions: the water-to-graphite electronic mass collision stopping power ratio, which is equal to 1.115, and the fluence correction factor which varies linearly with depth, as k(fl, all) = 0.9995 + 0.0048(zw-eq). The latter has been determined on the basis of experiments and numerical simulations.

DiPOLE: a 10 J, 10 Hz cryogenic gas cooled multi-slab nanosecond Yb:YAG laser.

PubMed

Banerjee, Saumyabrata; Ertel, Klaus; Mason, Paul D; Phillips, P Jonathan; De Vido, Mariastefania; Smith, Jodie M; Butcher, Thomas J; Hernandez-Gomez, Cristina; Greenhalgh, R Justin S; Collier, John L

2015-07-27

The Diode Pumped Optical Laser for Experiments (DiPOLE) project at the Central Laser Facility aims to develop a scalable, efficient high pulse energy diode pumped laser amplifier system based on cryogenic gas cooled, multi-slab ceramic Yb:YAG technology. We present recent results obtained from a scaled down prototype laser system designed for operation at 10 Hz pulse repetition rate. At 140 K, the system generated 10.8 J of energy in a 10 ns pulse at 1029.5 nm when pumped by 48 J of diode energy at 940 nm, corresponding to an optical to optical conversion efficiency of 22.5%. To our knowledge, this represents the highest pulse energy obtained from a cryo cooled Yb laser to date and the highest efficiency achieved by a multi-Joule diode pumped solid state laser system. Additionally, we demonstrated shot-to-shot energy stability of 0.85% rms for the system operated at 7 J, 10 Hz during several runs lasting up to 6 hours, with more than 50 hours in total. We also demonstrated pulse shaping capability and report on beam, wavefront and focal spot quality.

Method and apparatus for efficient photodetachment and purification of negative ion beams

DOEpatents

Beene, James R [Oak Ridge, TN; Liu, Yuan [Knoxville, TN; Havener, Charles C [Knoxville, TN

2008-02-26

Methods and apparatus are described for efficient photodetachment and purification of negative ion beams. A method of purifying an ion beam includes: inputting the ion beam into a gas-filled multipole ion guide, the ion beam including a plurality of ions; increasing a laser-ion interaction time by collisional cooling the plurality of ions using the gas-filled multipole ion guide, the plurality of ions including at least one contaminant; and suppressing the at least one contaminant by selectively removing the at least one contaminant from the ion beam by electron photodetaching at least a portion of the at least one contaminant using a laser beam.

A method for determining the conversion efficiency of multiple-cell photovoltaic devices

NASA Astrophysics Data System (ADS)

Glatfelter, Troy; Burdick, Joseph

A method for accurately determining the conversion efficiency of any multiple-cell photovoltaic device under any arbitrary reference spectrum is presented. This method makes it possible to obtain not only the short-circuit current, but also the fill factor, the open-circuit voltage, and hence the conversion efficiency of a multiple-cell device under any reference spectrum. Results are presented which allow a comparison of the I-V parameters of two-terminal, two- and three-cell tandem devices measured under a multiple-source simulator with the same parameters measured under different reference spectra. It is determined that the uncertainty in the conversion efficiency of a multiple-cell photovoltaic device obtained with this method is less than +/-3 percent.

In-use catalyst surface area and its relation to HC conversion efficiency and FTP emissions

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

Donahue, K.S.; Sabourin, M.A.; Larson, R.E.

1986-01-01

Surface area data, steady-state hydrocarbon conversion efficiency data, and hydrocarbon emissions results have been determined for catalysts collected by the U.S. Environmental Protection Agency from properly maintained 1981 and 1982 model year vehicles. Catalysts covered in this study were limited to those with three-way-plus-oxidation monolith technologies. Catalyst surface areas were measured using the BET method, conversion efficiencies were measured on an exhaust gas generator, and emissions results were determined using the Urban Driving Schedule of the Federal Test Procedure. Results indicate that correlation of catalyst surface area data with hydrocarbon conversion efficiency data and hydrocarbon emissions results is significant formore » the sample studied.« less

Estimation of coupling efficiency of optical fiber by far-field method

NASA Astrophysics Data System (ADS)

Kataoka, Keiji

2010-09-01

Coupling efficiency to a single-mode optical fiber can be estimated with the field amplitudes at far-field of an incident beam and optical fiber mode. We call it the calculation by far-field method (FFM) in this paper. The coupling efficiency by FFM is formulated including effects of optical aberrations, vignetting of the incident beam, and misalignments of the optical fiber such as defocus, lateral displacements, and angle deviation in arrangement of the fiber. As the results, it is shown the coupling efficiency is proportional to the central intensity of the focused spot, i.e., Strehl intensity of a virtual beam determined by the incident beam and mode of the optical fiber. Using the FFM, a typical optics in which a laser beam is coupled to an optical fiber with a lens of finite numerical aperture (NA) is analyzed for several cases of amplitude distributions of the incident light.

Effect of transverse nonuniformity of the rf field on the efficiency of microwave sources driven by linear electron beams

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

Nusinovich, G.S.; Sinitsyn, O.V.

This paper contains a simple analytical theory that allows one to evaluate the effect of transverse nonuniformity of the rf field on the interaction efficiency in various microwave sources driven by linear electron beams. The theory is, first, applied to the systems where the beams of cylindrical symmetry interact with rf fields of microwave circuits having Cartesian geometry. Also, various kinds of microwave devices driven by sheet electron beams (orotrons, clinotrons) are considered. The theory can be used for evaluating the efficiency of novel sources of coherent terahertz radiation.

Phased Array Technology with Phase and Amplitude Controlled Magnetron for Microwave Power Transmission

NASA Astrophysics Data System (ADS)

Shinohara, N.; Matsumoto, H.

2004-12-01

We need a microwave power transmitter with light weight and high DC-RF conversion efficiency for an economical SSPS (Space Solar Power System). We need a several g/W for a microwave power transmission (MPT) system with a phased array with 0.0001 degree of beam control accuracy (=tan-1 (100m/36,000km)) and over 80 % of DC-RF conversion efficiency when the weight of the 1GW-class SPS is below a several thousand ton - a several tens of thousand ton. We focus a microwave tube, especially magnetron by economical reason and by the amount of mass-production because it is commonly used for microwave oven in the world. At first, we have developed a phase controlled magnetron (PCM) with different technologies from what Dr. Brown developed. Next we have developed a phase and amplitude controlled magnetron (PACM). For the PACM, we add a feedback to magnetic field of the PCM with an external coil to control and stabilize amplitude of the microwave. We succeed to develop the PACM with below 10-6 of frequency stability and within 1 degree of an error in phase and within 1% of amplitude. We can control a phase and amplitude of the PACM and we have developed a phased array the PCMs. With the PCM technology, we have developed a small light weight MPT transmitter COMET (Compact Microwave Energy Transmitter) with consideration of heat radiation for space use and with consideration of mobility to space.

A long-pulse repetitive operation magnetically insulated transmission line oscillator.

PubMed

Fan, Yu-Wei; Zhong, Hui-Huang; Zhang, Jian-De; Shu, Ting; Liu, Jin Liang

2014-05-01

The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube. It has allowed us to generate 3.1 GW pulse of 40 ns duration in the single-pulse operation and 500 MW pulse of 25 ns duration in the repetition rate operation. However, because of the severe impedance mismatch, the power conversion efficiency is only about 4% in the repetition rate operation. In order to eliminate the impedance mismatch and obtain repetitive long-pulse high-power microwave (HPM), a series of experiments are carried out and the recent progress is presented in this paper. In the single-pulse operation, when the diode voltage is 466 kV and current is 41.6 kA, the radiated microwave power is above 2.2 GW, the pulse duration is above 102 ns, the microwave frequency is about 1.74 GHz, and the power conversion efficiency is about 11.5%. In the repetition rate operation, under the condition of the diode voltage about 400 kV, beam current about 38 kA, the radiated microwave power is about 1.0 GW, the pulse duration is about 85 ns. Moreover, the radiated microwave power and the pulse duration decline little by little when the shot numbers increase gradually. The experimental results show that the impedance matching is a vital factor for HPM systems and one of the major technical challenges is to improve the cathode for the repetition rate operation MILO.

Heterogeneously Nd3+ doped single nanoparticles for NIR-induced heat conversion, luminescence, and thermometry.

PubMed

Marciniak, Lukasz; Pilch, Aleksandra; Arabasz, Sebastian; Jin, Dayong; Bednarkiewicz, Artur

2017-06-22

The current frontier in nanomaterials engineering is to intentionally design and fabricate heterogeneous nanoparticles with desirable morphology and composition, and to integrate multiple functionalities through highly controlled epitaxial growth. Here we show that heterogeneous doping of Nd 3+ ions following a core-shell design already allows three optical functions, namely efficient (η > 72%) light-to-heat conversion, bright NIR emission, and sensitive (S R > 0.1% K -1 ) localized temperature quantification, to be built within a single ca. 25 nm nanoparticle. Importantly, all these optical functions operate within the transparent biological window of the NIR spectral region (λ exc ∼ 800 nm, λ emi ∼ 860 nm), in which light scattering and absorption by tissues and water are minimal. We find NaNdF 4 as a core is efficient in absorbing and converting 808 nm light to heat, while NaYF 4 :1%Nd 3+ as a shell is a temperature sensor based on the ratio-metric luminescence reading but an intermediate inert spacer shell, e.g. NaYF 4 , is necessary to insulate the heat convertor and thermometer by preventing the possible Nd-Nd energy relaxation. Moreover, we notice that while temperature sensitivity and luminescence intensity are optically stable, increased excitation intensity to generate heat above room temperature may saturate the sensing capacity of temperature feedback. We therefore propose a dual beam photoexcitation scheme as a solution for possible light-induced hyperthermia treatment.

Fully interferometric controllable anomalous refraction efficiency using cross modulation with plasmonic metasurfaces.

PubMed

Liu, Zhaocheng; Chen, Shuqi; Li, Jianxiong; Cheng, Hua; Li, Zhancheng; Liu, Wenwei; Yu, Ping; Xia, Ji; Tian, Jianguo

2014-12-01

We present a method of fully interferometric, controllable anomalous refraction efficiency by introducing cross-modulated incident light based on plasmonic metasurfaces. Theoretical analyses and numerical simulations indicate that the anomalous and ordinary refracted beams generated from two opposite-helicity incident beams and following the generalized Snell's law will have a superposition for certain incident angles, and the anomalous refraction efficiency can be dynamically controlled by changing the relative phase of the incident sources. As the incident wavelength nears the resonant wavelength of the plasmonic metasurfaces, two equal-amplitude incident beams with opposite helicity can be used to control the anomalous refraction efficiency. Otherwise, two unequal-amplitude incident beams with opposite helicity can be used to fully control the anomalous refraction efficiency. This Letter may offer a further step in the development of controllable anomalous refraction.

Microscopy of biological sample through advanced diffractive optics from visible to X-ray wavelength regime.

PubMed

Di Fabrizio, Enzo; Cojoc, Dan; Emiliani, Valentina; Cabrini, Stefano; Coppey-Moisan, Maite; Ferrari, Enrico; Garbin, Valeria; Altissimo, Matteo

2004-11-01

The aim of this report is to demonstrate a unified version of microscopy through the use of advanced diffractive optics. The unified scheme derives from the technical possibility of realizing front wave engineering in a wide range of electromagnetic spectrum. The unified treatment is realized through the design and nanofabrication of phase diffractive elements (PDE) through which wave front beam shaping is obtained. In particular, we will show applications, by using biological samples, ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy combined with X-ray fluorescence. We report some details on the design and physical implementation of diffractive elements that besides focusing also perform other optical functions: beam splitting, beam intensity, and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of micro-beads surrounding a cell as an array of tweezers and for arraying and sorting microscopic size biological samples. Another application is the Gauss to Laguerre-Gauss mode conversion, which allows for trapping and transfering orbital angular momentum of light to micro-particles immersed in a fluid. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for diffractive optics implementation. High-resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in x-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field x-ray microscopy. Besides the topographic information, fluorescence allows detection of certain chemical elements (Cl, P, Sc, K) in the same setup, by changing the photon energy of the x-ray beam. (c) 2005 Wiley-Liss, Inc.

Theoretical study on second-harmonic generation of focused vortex beams

NASA Astrophysics Data System (ADS)

Tang, Daolong; Wang, Jing; Ma, Jingui; Zhou, Bingjie; Yuan, Peng; Xie, Guoqiang; Zhu, Heyuan; Qian, Liejia

2018-03-01

Second-harmonic generation (SHG) provides a promising route for generating vortex beams of both short wavelength and large topological charge. Here we theoretically investigate the efficiency optimization and beam characteristics of focused vortex-beam SHG. Owing to the increasing beam divergence, vortex beams have distinct features in SHG optimization compared with a Gaussian beam. We show that, under the noncritical phase-matching condition, the Boyd and Kleinman prediction of the optimal focusing parameter for Gaussian-beam SHG remains valid for vortex-beam SHG. However, under the critical phase-matching condition, which is sensitive to the beam divergence, the Boyd and Kleinman prediction is no longer valid. In contrast, the optimal focusing parameter for maximizing the SHG efficiency strongly depends on the vortex order. We also investigate the effects of focusing and phase-matching conditions on the second-harmonic beam characteristics.

Narrow-linewidth, quasi-continuous-wave ASE source based on a multiple-pass Nd:YAG zigzag slab amplifier configuration.

PubMed

Chen, Xiaoming; Lu, Yanhua; Hu, Hao; Tong, Lixin; Zhang, Lei; Yu, Yi; Wang, Juntao; Ren, Huaijin; Xu, Liu

2018-03-05

We present investigations into a narrow-linewidth, quasi-continuous-wave pulsed all-solid-state amplified spontaneous emission (ASE) source by use of a novel multiple-pass zigzag slab amplifier. The SE fluorescence emitted from a Nd:YAG slab active medium acts as the seed and is amplified back and forth 8 times through the same slab. Thanks to the angular multiplexing nature of the zigzag slab, high-intensity 1064-nm ASE output can be produced without unwanted self-lasing in this configuration. Experimentally, the output energy, optical conversion efficiency, pulse dynamics, spectral property, and beam quality of the ASE source are studied when the Nd:YAG slab end-pumped by two high-brightness laser diode arrays. The maximum single pulse energy of 347 mJ is generated with an optical efficiency of ~5.9% and a beam quality of 3.5/17 in the thickness/width direction of the slab. As expected, smooth pulses without relaxing spikes and continuous spectra are achieved. Moreover, the spectral width of the ASE source narrows versus the pump energy, getting a 3-dB linewidth of as narrow as 20 pm (i.e. 5.3 GHz). Via the sum frequency generation, high-intensity, smooth-pulse, and narrow-linewidth ASE sources are preferred for solving the major problem of saturation of the mesospheric sodium atoms and can create a much brighter sodium guide star to meet the needs of adaptive imaging applications in astronomy.

Evidence of significant down-conversion in a Si-based solar cell using CuInS2/ZnS core shell quantum dots

NASA Astrophysics Data System (ADS)

Gardelis, Spiros; Nassiopoulou, Androula G.

2014-05-01

We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS2/ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion.

Propagation of various dark hollow beams in a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Cai, Yangjian; He, Sailing

2006-02-01

Propagation of a dark hollow beam (DHB) of circular, elliptical or rectangular symmetry in a turbulent atmosphere is investigated. Analytical formulas for the average intensity of various DHBs propagating in a turbulent atmosphere are derived in a tensor form based on the extended Huygens-Fresnel integral. The intensity and spreading properties of the DHBs in a turbulent atmosphere are studied numerically. It is found that after a long propagation distance a dark hollow beam of circular or noncircular eventually becomes a circular Gaussian beam (without dark hollow) in a turbulent atmosphere, which is much different from its propagation properties in free space. The conversion from a DHB to a circular Gaussian beam becomes quicker and the beam spot in the far field spreads more rapidly for a larger structure constant, a shorter wavelength, a lower beam order and a smaller waist size of the initial beam.

Propagation of various dark hollow beams in a turbulent atmosphere.

PubMed

Cai, Yangjian; He, Sailing

2006-02-20

Propagation of a dark hollow beam (DHB) of circular, elliptical or rectangular symmetry in a turbulent atmosphere is investigated. Analytical formulas for the average intensity of various DHBs propagating in a turbulent atmosphere are derived in a tensor form based on the extended Huygens-Fresnel integral. The intensity and spreading properties of the DHBs in a turbulent atmosphere are studied numerically. It is found that after a long propagation distance a dark hollow beam of circular or noncircular eventually becomes a circular Gaussian beam (without dark hollow) in a turbulent atmosphere, which is much different from its propagation properties in free space. The conversion from a DHB to a circular Gaussian beam becomes quicker and the beam spot in the far field spreads more rapidly for a larger structure constant, a shorter wavelength, a lower beam order and a smaller waist size of the initial beam.

Designing Light Beam Transmittance Measuring Tool Using a Laser Pointer

NASA Astrophysics Data System (ADS)

Nuroso, H.; Kurniawan, W.; Marwoto, P.

2016-08-01

A simple instrument used for measuring light beam transmittance percentage made of window film has been developed. The instrument uses a laser pointer of 405 nm and 650 nm ±10% as a light source. Its accuracy approaches 80%. Transmittance data was found by comparing the light beam before and after passing the window film. The light intensity measuring unit was deleted by splitting the light source into two beams through a beam splitter. The light beam was changed into resistance by a NORP12 LDR sensor designed at a circuit of voltage divider rule of Khirchoff's laws. This conversion system will produce light beam intensity received by the sensor to become an equal voltage. This voltage will, then, be presented on the computer screen in the form of a real time graph via a 2.0 USB data transfer.

High-Efficiency Photovoltaic System Using Partially-Connected DC-DC Converter

NASA Astrophysics Data System (ADS)

Uno, Masatoshi; Kukita, Akio; Tanaka, Koji

Power conversion electronics for photovoltaic (PV) systems are desired to operate as efficiently as possible to exploit the power generated by PV modules. This paper proposes a novel PV system in which a dc-dc converter is partially connected to series-connected PV modules. The proposed system achieves high power-conversion efficiency by reducing the passing power and input/output voltages of the converter. The theoretical operating principle was experimentally validated. Resultant efficiency performances of the proposed and conventional systems demonstrated that the proposed system was more efficient in terms of power conversion though the identical converter was used for the both systems.

Radiation energy conversion in space

NASA Technical Reports Server (NTRS)

Billman, K. W.

1979-01-01

Topics discussed at the third NASA conference on radiant energy conversion are reviewed. The unconcentrated-photovoltaic-generation version of a solar power satellite is described, noting that it will consist of a 21.3 x 5.3-sq-km silicon-solar-cell array expected to provide 17 Gw of electrical power, with 1 km in diam transmitters oriented to beam 2.45 GHz microwave power to two receiving/rectifying 'rectennas' on earth. The Solares space-energy-system concept, designed for providing a large fraction of the world's energy needs at costs comparable to those of future coal/nuclear alternative, is considered, as are subsystems for improving the economics of the solar power satellite. A concept proposing the use of relativistic-electron-storage rings for electron-beam energy transmission and storage, and a report on the production of a high temperature plasma with concentrated solar radiation are taken into account. Laser-conversion systems, including the direct-solar-pumped space laser, and the telec-powered spacecraft, are discussed.