Science.gov

Sample records for high gain fel

  1. Where do we stand with high gain FEL simulations?

    NASA Astrophysics Data System (ADS)

    Travish, Gil

    1997-06-01

    Computer technology improvements have allowed for more complete and detailed free electron laser simulations, yet the demands of the large number of new experiments and proposed projects has outpaced the capability and availability of present codes. This paper, based on a talk given at the conference of these proceedings, presents a brief assessment of Free Electron Laser (FEL) codes, their availability and features, as well as some opinions on what direction the FEL code community should take for the near future. The discussion of FEL codes is restricted here to ones for high gain amplifiers: no codes for oscillators, waveguides or exotic configurations are considered.

  2. Dispersion relations for 1D high-gain FELs

    SciTech Connect

    Webb, S.D.; Litvinenko, V.N.

    2010-08-23

    We present analytical results for the one-dimensional dispersion relation for high-gain FELs. Using kappa-n distributions, we obtain analytical relations between the dispersion relations for various order kappa distributions. Since an exact solution exists for the kappa-1 (Lorentzian) distribution, this provides some insight into the number of modes on the way to the Gaussian distribution.

  3. STARS A Two Stage High Gain Harmonic Generation FEL Demonstrator

    SciTech Connect

    M. Abo-Bakr; W. Anders; J. Bahrdt; P. Budz; K.B. Buerkmann-Gehrlein; O. Dressler; H.A. Duerr; V. Duerr; W. Eberhardt; S. Eisebitt; J. Feikes; R. Follath; A. Gaupp; R. Goergen; K. Goldammer; S.C. Hessler; K. Holldack; E. Jaeschke; Thorsten Kamps; S. Klauke; J. Knobloch; O. Kugeler; B.C. Kuske; P. Kuske; A. Meseck; R. Mitzner; R. Mueller; M. Neeb; A. Neumann; K. Ott; D. Pfluckhahn; T. Quast; M. Scheer; Th. Schroeter; M. Schuster; F. Senf; G. Wuestefeld; D. Kramer; Frank Marhauser

    2007-08-01

    BESSY is proposing a demonstration facility, called STARS, for a two-stage high-gain harmonic generation free electron laser (HGHG FEL). STARS is planned for lasing in the wavelength range 40 to 70 nm, requiring a beam energy of 325 MeV. The facility consists of a normal conducting gun, three superconducting TESLA-type acceleration modules modified for CW operation, a single stage bunch compressor and finally a two-stage HGHG cascaded FEL. This paper describes the faciliy layout and the rationale behind the operation parameters.

  4. Possibility of a high-power, high-gain amplifier FEL

    SciTech Connect

    Nguyen, D. C.; Freund, H. P.

    2002-01-01

    High-gain amplifier FEL offer many unique advantages such as robust operation without a high-Q optical cavity and potentially high extraction eaciencies with the use of tapered wigglers. Although a high average power, cw amplifier FEL has not been demonstrated, many key physics issues such as electron beam brightness requirements, single-pass gains, saturation, etc. have been resolved. In this paper, we study the feasibility of a high-power FEL based on the high-gain amplifier concept. We show that with suitable electron beam parameters, i.e. high peak current, low emittance, low energy spread, and sufficient tapered wiggler length, peak output power of 1 QW and optical pulse energy of 8 mJ can be achieved. We also outline a possible configuration of a high-power, high-gain amplifier FEL with energy recovery.

  5. Steady State Analysis of Short-wavelength, High-gainFELs in a Large Storage Ring

    SciTech Connect

    Huang, Z.; Bane, K.; Cai, Y.; Chao, A.; Hettel, R.; Pellegrini, C.; /UCLA

    2007-10-15

    Storage ring FELs have operated successfully in the low-gain regime using optical cavities. Discussions of a high-gain FEL in a storage ring typically involve a special bypass to decouple the FEL interaction from the storage ring dynamics. In this paper, we investigate the coupled dynamics of a high-gain FEL in a large storage ring such as PEP and analyze the equilibrium solution. We show that an FEL in the EUV and soft x-ray regimes can be integrated into a very bright storage ring and potentially provides three orders of magnitude improvement in the average brightness at these radiation wavelengths. We also discuss possibilities of seeding with HHG sources to obtain ultra-short, high-peak power EUV and soft x-ray pulses.

  6. Strong focusing influence on high gain FEL characteristics

    SciTech Connect

    Smirnov, A.; Varfolomeev, A.

    1995-12-31

    The use of intrinsic alternating focusing in a linac-driven FEL with planar undulator is considered numerically. The analysis is done on the basis of TDA code for soft X-ray FEL with FD lattice implementing focusing of quadrupole and periodic sextupole type. The influence of the focusing (type and phase advance) on FEL performance and the reasons of difference in FEL performance for focusing of two kinds are analyzed. A possibility of some kind of beam conditioning for intrinsic focusing is discussed.

  7. A Coherent Compton Backscattering High Gain FEL using an X-Band Microwave Undulator

    SciTech Connect

    Tantawi, S.; Dolgashev, V.; Nantista, C.; Pellegrini, C.; Rosenzweig, J.; Travish, G.; /UCLA

    2005-12-14

    High power microwave sources at X-Band, delivering 400 to 500 of megawatts for about 400 ns, have been recently developed. These sources can power a microwave undulator with short period and large gap, and can be used in short wavelength FELs reaching the nm region at a beam energy of about 1 GeV. We present here an experiment designed to demonstrate that microwave undulators have the field quality needed for high gain FELs.

  8. Analysis of FEL-based CeC amplification at high gain limit

    SciTech Connect

    Wang, G.; Litvinenko, V.; Jing, Y.

    2015-05-03

    An analysis of Coherent electron Cooling (CeC) amplifier based on 1D Free Electron Laser (FEL) theory was previously performed with exact solution of the dispersion relation, assuming electrons having Lorentzian energy distribution. At high gain limit, the asymptotic behavior of the FEL amplifier can be better understood by Taylor expanding the exact solution of the dispersion relation with respect to the detuning parameter. In this work, we make quadratic expansion of the dispersion relation for Lorentzian energy distribution and investigate how longitudinal space charge and electrons’ energy spread affect the FEL amplification process.

  9. Optimization of single-step tapering amplitude and energy detuning for high-gain FELs

    NASA Astrophysics Data System (ADS)

    Li, He-Ting; Jia, Qi-Ka

    2015-01-01

    We put forward a method to optimize the single-step tapering amplitude of undulator strength and initial energy tuning of electron beam to maximize the saturation power of high gain free-electron lasers (FELs), based on the physics of longitudinal electron beam phase space. Using the FEL simulation code GENESIS, we numerically demonstrate the accuracy of the estimations for parameters corresponding to the linac coherent light source and the Tesla test facility.

  10. COMPARISON OF TWO DIFFERENT WAVELENGTH TUNING SCHEMES IN A SEEDED HIGH-GAIN FEL.

    SciTech Connect

    SHAFTAN,T.; YU,L.H.

    2004-08-04

    In the following text we analyze and compare results of the two publications ([1], [2]), dedicated to development of the tunable high-gain Free Electron laser (FEL), seeded by an external source. As a conclusion we summarize similarities and differences between these concepts. This note is initiated by the polemics on the similarity of two different schemes of the wavelength tuning in a seeded high-gain FEL. Below we will be calling the scheme, presented by S. Biedron, S, Milton and H. Freund in Nuclear Instruments and Methods of 2001 ([1]), as the first (1st) scheme. The scheme that we developed and presented in the BNL preprint ([2]) will be called as the second (2nd) scheme. The following analysis provides important information on similarities and differences between both techniques. We start by considering the first approach. As we understand, the goal of the Modular Approach is to make X-ray FEL design more flexible [1]. Usual linac-based FELs begin from a long linac with bunch compressor(s) followed by an FEL magnetic system. The essence of the Modular Approach is to break a machine into modules and then recombine these modules in a more efficient way (from the point of view of monetary and/or time constraints). The chapter 3.5 of [1] presents some basic example of Modular Approach. We have studied the scheme, discussed in [1] and illustrated in Fig. 2. Even though very few details of the scheme were presented, it was still sufficient to obtain a complete qualitative picture. Let us begin with the usual phase space of the microbunched beam, which enters a radiator in a prebunched FEL (Fig. 1). The sharp spike (in blue) represents the longitudinal density bunching, which will be the main subject of interest in this discussion. The key principle of a seeded high-gain FEL optimization is to establish this kind of the electron beam phase space at the entrance of the radiator.

  11. An analysis of the saturation of a high gain FEL

    SciTech Connect

    Gluckstern, R.L.; Okamoto, Hiromi . Dept. of Physics); Krinsky, S. )

    1992-12-01

    We study the saturated state of an untapered free electron laser in the Compton regime, arising after exponential amplification of an initial low level of radiation by an initially monoenergetic, unbunched electron beam. The saturated state of the FEL is described by oscillations about an equilibrium state. Using the two invariants of the motion, and certain assumptions motivated by computer simulations, we provide approximate analytic descriptions of the radiation field and electron distribution in the saturation regime. We first consider a one-dimensional approximation, and later extend our approach to treat an electron beam of finite radial extent. Of note is a result on the radiated power in the case of an electron beam with small radius.

  12. High gain FEL amplification of charge modulation caused by a hadron

    SciTech Connect

    Litvinenko,V.; Ben-Zvi, I.; Hao, Y.; Kayran, D.; Pozdeyev, E.; Wang, G.; Reiche, S.; Shevchenko, O.; Vinokurov, N. A.

    2008-08-24

    In scheme of coherent electron cooling (CeC) [1,2], a modulation of electron beam density induced by a copropagation hadron is amplified in high gain FEL. The resulting amplified modulation of electron beam, its shape, form and its lethargy determine number of important properties of the coherent electron cooling. In this talk we present both analytical and numerical (using codes RON [3] and Genesis [4]) evaluations of the corresponding Green functions. We also discuss influence of electron beam parameters on the FEL response.

  13. Oscillator Seeding of a High Gain Harmonic Generation FEL in a Radiator-First Configuration

    SciTech Connect

    Gandhi, P.; Wurtele, J.; Penn, G.; Reinsch, M.

    2012-05-20

    A longitudinally coherent X-ray pulse from a high repetition rate free electron laser (FEL) is desired for a wide variety of experimental applications. However, generating such a pulse with a repetition rate greater than 1 MHz is a significant challenge. The desired high repetition rate sources, primarily high harmonic generation with intense lasers in gases or plasmas, do not exist now, and, for the multi-MHz bunch trains that superconducting accelerators can potentially produce, are likely not feasible with current technology. In this paper, we propose to place an oscillator downstream of a radiator. The oscillator generates radiation that is used as a seed for a high gain harmonic generation (HGHG) FEL which is upstream of the oscillator. For the first few pulses the oscillator builds up power and, until power is built up, the radiator has no HGHG seed. As power in the oscillator saturates, the HGHG is seeded and power is produced. The dynamics and stability of this radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations. A numerical example is presented for a soft X-ray FEL.

  14. Effects of undulator interruptions on the performance of high-gain FEL amplifiers

    SciTech Connect

    Kim, K.J.; Xie, M.; Pelligrini, C.

    1995-12-31

    The high-gain amplifiers for short wavelength free electron lasers (FELs) such as the LCLS project require a long undulator. The construction of the undulator as well as the FEL operation would become easier if the undulator could be interrupted with drift sections every few gain lengths. We have investigated the influence of such interruption on the FEL performances. Three effects are considered: (i) the diffraction loss, (ii) the phase mismatch and, (iii) the phase smearing due to velocity spread and to dispersion errors. The effect (i) is the loss during the process in which the optical mode in a section of the undulator leaves the undulator, propagates through the free space and then re-enters and re-adjusts in the next section. The effect (ii) is the fact that the phase of the optical beam is displaced with respect to the electrons density modulation for optical FEL interaction due to the slippage of the electron beam in the interruption region. The effect (iii) is the fact that electrons velocity spread, emittance, and dispersion due to misalignment of the quadrupoles used for additional focusing lead to a reduction of the bunching factor. We present an approximate analysis of these effects. When applied to the LCLS parameters, we find that the effect (i) is negligible, the effect (ii) gives a condition on the length of the drift section, and the effects (iii) are small, but could be non-negligible if there are sufficient number of interruptions.

  15. DEMONSTRATION OF 3D EFFECTS WITH HIGH GAIN AND EFFICIENCY IN A UV FEL OSCILLATOR

    SciTech Connect

    Stephen Benson; George Biallas; Keith Blackburn; James Boyce; Donald Bullard; James Coleman; Cody Dickover; David Douglas; Forrest Ellingsworth; Pavel Evtushenko; Carlos Hernandez-Garcia; Christopher Gould; Joseph Gubeli; David Hardy; Kevin Jordan; John Klopf; James Kortze; Robert Legg; Matthew Marchlik; Steven Moore; George Neil; Thomas Powers; Daniel Sexton; Michelle D. Shinn; Christopher Tennant; Richard Walker; Anne Watson; Gwyn Williams; Frederick Wilson; Shukui Zhang

    2011-03-01

    We report on the performance of a high gain UV FEL oscillator operating on an energy recovery linac at Jefferson Lab. The high brightness of the electron beam leads to both gain and efficiency that cannot be reconciled with a one-dimensional model. Three-dimensional simulations do predict the performance with reasonable precision. Gain in excess of 100% per pass and an efficiency close to 1/2NW, where NW is the number of wiggler periods, is seen. The laser mirror tuning curves currently permit operation in the wavelength range of 438 to 362 nm. Another mirror set allows operation at longer wavelengths in the red with even higher gain and efficiency.

  16. Evolution of electron beam phase space distribution in a high-gain FEL

    SciTech Connect

    Webb,S.D.; Litvinenko, V. N.

    2009-08-23

    FEL-based coherent electron cooling (CEC) offers a new avenue to achieve high luminosities in high energy colliders such as RHIC, LHC, and eRHIC. Traditional treatments consider the FEL as an amplifier of optical waves with specific initial conditions, focusing on the resulting field. CEC requires knowledge of the phase space distribution of the electron beam in the FEL. We present 1D analytical results for the phase space distribution of an electron beam with an arbitrary initial current profile, and discuss approaches of expanding to 3D results.

  17. PRELIMINARY MEASURMENTS OF THE HIGH-GAIN FEL RADIATION PROPERTIES ALONG THE RADIATOR.

    SciTech Connect

    SHAFTAN,T.; LOOS,H.; SHEEHY,B.; YU,L.H.

    2004-08-29

    We present preliminary experimental results on evolution of properties of the DUV FEL [1,2] radiation along the radiator. Intercepting the electron beam at the different locations inside the undulator we recorded and analyzed transverse profiles, spectra and intensity of the FEL output. Shot-to-shot fluctuations of the FEL radiation may significantly affect the accuracy of measurement. In the paper we present and discuss a single-shot measurement technique, based on a special imaging system.

  18. Development of a 3D FEL code for the simulation of a high-gain harmonic generation experiment.

    SciTech Connect

    Biedron, S. G.

    1999-02-26

    Over the last few years, there has been a growing interest in self-amplified spontaneous emission (SASE) free-electron lasers (FELs) as a means for achieving a fourth-generation light source. In order to correctly and easily simulate the many configurations that have been suggested, such as multi-segmented wigglers and the method of high-gain harmonic generation, we have developed a robust three-dimensional code. The specifics of the code, the comparison to the linear theory as well as future plans will be presented.

  19. HIGH AVERAGE POWER OPTICAL FEL AMPLIFIERS.

    SciTech Connect

    BEN-ZVI, ILAN, DAYRAN, D.; LITVINENKO, V.

    2005-08-21

    Historically, the first demonstration of the optical FEL was in an amplifier configuration at Stanford University [l]. There were other notable instances of amplifying a seed laser, such as the LLNL PALADIN amplifier [2] and the BNL ATF High-Gain Harmonic Generation FEL [3]. However, for the most part FELs are operated as oscillators or self amplified spontaneous emission devices. Yet, in wavelength regimes where a conventional laser seed can be used, the FEL can be used as an amplifier. One promising application is for very high average power generation, for instance FEL's with average power of 100 kW or more. The high electron beam power, high brightness and high efficiency that can be achieved with photoinjectors and superconducting Energy Recovery Linacs (ERL) combine well with the high-gain FEL amplifier to produce unprecedented average power FELs. This combination has a number of advantages. In particular, we show that for a given FEL power, an FEL amplifier can introduce lower energy spread in the beam as compared to a traditional oscillator. This properly gives the ERL based FEL amplifier a great wall-plug to optical power efficiency advantage. The optics for an amplifier is simple and compact. In addition to the general features of the high average power FEL amplifier, we will look at a 100 kW class FEL amplifier is being designed to operate on the 0.5 ampere Energy Recovery Linac which is under construction at Brookhaven National Laboratory's Collider-Accelerator Department.

  20. INITIAL GAIN MEASUREMENTS OF A 800 NM SASE FEL, VISA.

    SciTech Connect

    FRIGOLA,P.; MUROKH,A.; ET AL; BABZIEN,M.; BEN-ZVI,I.; JOHNSON,E.; MALONE,R.

    2000-08-13

    The VISA (Visible to Infrared SASE Amplifier) FEL is designed to obtain high gain at a radiation wavelength of 800nm. The FEL uses the high brightness electron beam of the Accelerator Test Facility (ATF), with energy of 72MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6mm and a period of 1.8cm. To obtain large gain the beam and undulator axis have to be aligned to better than 50{micro}m. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations.

  1. Initial Gain Measurements of a 800nm SASE FEL, VISA

    SciTech Connect

    Carr, Roger

    2002-08-14

    The VISA (Visible to Infrared SASE Amplifier) FEL is designed to obtain high gain at a radiation wavelength of 800nm. The FEL uses the high brightness electron beam of the Accelerator Test Facility (ATF), with energy of 72MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6mm and a period of 1.8cm. To obtain large gain the beam and undulator axis have to be aligned to better than 50{micro}m. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations.

  2. Initial Gain Measurements of a 800nmm SASE FEL, VISA

    NASA Astrophysics Data System (ADS)

    Tremaine, A.; Frigola, P.; Murokh, A.; Musumeci, P.; Pellegrini, C.

    2002-08-01

    The VISA (Visible to Infrared SASE Amplifier) FEL is designed to obtain high gain at a radiation wavelength of 800nm. The FEL uses the high brightness electron beam of the Accelerator Test Facility (ATF), with energy of 72MeV. VISA uses a novel, 4 m long, strong focussing undulator with a gap of 6mm and a period of 1.8cm. To obtain large gain the beam and undulator axis have to be aligned to better than 50mm. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations.

  3. Initial gain measurements of an 800 nm SASE FEL, VISA

    NASA Astrophysics Data System (ADS)

    Frigola, P.; Murokh, A.; Musumeci, P.; Pellegrini, C.; Reiche, S.; Rosenzweig, J.; Tremaine, A.; Babzien, M.; Ben-Zvi, I.; Johnson, E.; Malone, R.; Rakowsky, G.; Skaritka, J.; Wang, X. J.; Van Bibber, K. A.; Bertolini, L.; Hill, J. M.; Le Sage, G. P.; Libkind, M.; Toor, A.; Carr, R.; Cornacchia, M.; Klaisner, L.; Nuhn, H.-D.; Ruland, R.; Nguyen, D. C.

    2001-12-01

    The Visible to Infrared SASE Amplifier (VISA) FEL is designed to obtain high gain at a radiation wavelength of 800 nm. The FEL uses the high brightness electron beam of the Accelerator Test Facility (ATF), with energy of 72 MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6 mm and a period of 1.8 cm. To obtain large gain the beam and undulator axis have to be aligned to better than 5 μm. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations.

  4. Simulation of the short pulse effects in the start-up from noise in high-gain FELS

    SciTech Connect

    Hahn, S.J.; Kim, K.J.

    1995-12-31

    The spatio-temporal evolution of high-gain free electron lasers from noise is investigated by 1-D simulation calculation. To understand the discrepancy between the experimental result and theoretical prediction of the self-amplified spontaneous emission (SASE), the strong slippage effect in the short pulse electron beam and the coherent bunched beam effect are considered. When the length over which the electron density varies significantly is comparable or smaller than the FEL wavelength, the initial noise level would be increased due to the enhanced coherence between electrons. With a proper computer modeling of the start-up from noise including the energy spread, the overall performance and characteristics of SASE are studied. This work will be helpful to increase the credibility of the simulation calculation to predict the SASE performance in all wave-length regions.

  5. Status and initial commissioning of a high gain 800 nm SASE FEL

    NASA Astrophysics Data System (ADS)

    Tremaine, A.; Frigola, P.; Murokh, A.; Musumeci, P.; Pellegrini, C.; Rosenzweig, J.; Babzien, M.; Ben-Zvi, I.; Johnson, E.; Malone, R.; Rakowsky, G.; Skaritka, J.; Wang, X. J.; Yu, L. H.; Van Bibber, K. A.; Hill, J. M.; Le Sage, G. P.; Carr, R.; Cornacchia, M.; Nuhn, H.-D.; Ruland, R.; Nguyen, D. C.

    2000-05-01

    We describe the status and initial commissioning of the Visible to Infrared SASE Amplifier (VISA) experiment. VISA uses a strong focusing 4 m undulator, the Brookhaven National Laboratory ATF linac with an energy of 72 MeV, and a photoinjector electron source. The VISA fundamental radiation wavelength is near 800 nm and the power expected at saturation is near 60 MW. Power, angular and spectral measurements are planned for the VISA radiation and these results will be analyzed and compared with SASE FEL theory and computer simulation. In addition, the induced electron beam micro-bunching will be measured using coherent transition radiation.

  6. FEL gain optimisation and spontaneous radiation

    SciTech Connect

    Bali, L.M.; Srivastava, A.; Pandya, T.P.

    1995-12-31

    Colson have evaluated FEL gains for small deviations from perfect electron beam injection, with radiation of the same polarisation as that of the wiggler fields. We find that for optimum gain the polarisation of the optical field should be the same as that of the spontaneous emission under these conditions. With a helical wiggler the axial oscillations resulting from small departures from perfect electron beam injection lead to injection dependent unequal amplitudes and phases of the spontaneous radiation in the two transverse directions. Viewed along the axis therefore the spontaneous emission is elliptically polarised. The azimuth of the ellipse varies with the difference of phase of the two transverse components of spontaneous emission but the eccentricity remains the same. With planar wigglers the spontaneous emission viewed in the axial direction is linearly polarised, again with an injection dependent azimuth. For optimum coherent gain of a radiation field its polarisation characteristics must be the same as those of the spontaneous radiation with both types of wiggler. Thus, with a helical wiggler and the data reported earlier, an increase of 10% in the FEL gain at the fundamental frequency and of 11% at the fifth harmonic has been calculated in the small gain per pass limit. Larger enhancements in gain may result from more favourable values of input parameters.

  7. Gain results for low voltage FEL

    SciTech Connect

    Shaw, A.; Stuart, R.A.; Al-Shamma`a, A.

    1995-12-31

    We have designed and constructed a low voltage (130 kV) FEL system capable of operating in the microwave frequency range for which the electron beam current is cw (rather than pulsed) in time at a level of {approximately} 12 mA. The gain of this system has been measured as a function of the electron beam accelerating voltage and current level, and the input microwave frequency (8-10 GHz). The results are compared with the predictions of a simple theoretical model.

  8. A high-power compact regenerative amplifier FEL

    SciTech Connect

    Nguyen, D.C.; Sheffield, R.L.; Fortgang, C.M.; Kinross-Wright, J.M.; Ebrahim, N.A.; Goldstein, J.C.

    1997-08-01

    The Regenerative Amplifier FEL (RAFEL) is a new FEL approach aimed at achieving the highest optical power from a compact rf-linac FEL. The key idea is to feed back a small fraction (< 10%) of the optical power into a high-gain ({approximately}10{sup 5} in single pass) wiggler to enable the FEL to reach saturation in a few passes. This paper summarizes the design of a high-power compact regenerative amplifier FEL and describes the first experimental demonstration of the RAFEL concept.

  9. Small-signal gain in a gas-loaded FEL

    SciTech Connect

    Goloviznin, V.V.; Amersfoort, P.W. van

    1995-12-31

    At present, existing FEL facilities operate in the infrared and visible ranges of wavelengths. Generation of shorter waves (in the VUV and X-ray region) is of great scientific interest, but this would require a very expensive accelerator which could provide a high-current electron beam in the GeV-range of energies. A promising way to relax requirements on electron energy by introduction of a gas into the optical cavity was proposed nearly ten years ago. For small deviations from the vacuum wavelength, the idea was confirmed in experiments performed in Stanford; however, a detailed theory of such a device is still not developed. We present an analysis of the small-signal gain in a gas-loaded free-electron laser. Multiple scattering of electrons by the atoms of the gas inside the optical cavity is shown to lead to two additional effects, as compared to the case of a vacuum FEL: a loss of coherence between different parts of the electron trajectory and an enhancement of the phase {open_quotes}jitter{close_quotes}. Both effects become increasingly important at short wavelengths and significantly reduce the small-signal gain per pass. In 1D approximation analytical expressions are obtained and numerical calculations are made to estimate beam and undulator parameters necessary for lasing in the vacuum ultraviolet. Hydrogen-filled FELs are shown to have good prospects for this at today`s technological level. To operate in the range of wavelengths 125-140 nm, an electron beam should have an energy above 50 MeV and a good quality: a normalised emittance of the order of 5{pi} mm-mrad and an energy spread below 10{sup -3}. All these parameters are achieveable with modern linacs and photoinjectors.

  10. FEL gain calculation for imperfectly matched electron beams

    NASA Astrophysics Data System (ADS)

    Swent, R. L.; Berryman, K. W.

    1995-04-01

    We present here the details of an analytical small-signal gain calculation. The analysis builds on the basic one-dimensional analytical calculation by modeling the effects of finite electron beam size and imperfect matching of the electron beam to the wiggler. The calculation uses TRANSPORT [SLAC-91, Rev. 2 (1977)] parameters to describe the electron beam in order to easily take the output of beam transport calculations and use them as the input for FEL gain calculations. The model accepts an arbitrary TRANSPORT beam and includes the effects of energy spread, beam size, betatron oscillations, and focussing in the wiggle plane. The model has allowed us to calculate the range over which our FEL can be tuned by changing the electron energy alone (i.e., without changing any magnets).

  11. FEL and Optical Klystron Gain for an Electron Beam with Oscillatory Energy Distribution

    SciTech Connect

    Stupakov, G.; Ding, Y.; Huang, Z.; /SLAC

    2009-12-09

    If the energy spread of a beam is larger then the Pierce parameter, the FEL gain length increases dramatically and the FEL output gets suppressed. We show that if the energy distribution of such a beam is made oscillatory on a small scale, the gain length can be considerably decreased. Such an oscillatory energy distribution is generated by first modulating the beam energy with a laser via the mechanism of inverse FEL, and then sending it through a strong chicane. We show that this approach also works for the optical klystron enhancement scheme. Our analytical results are corroborated by numerical simulations.

  12. Gain enhancement plasma-loaded FEL in the presence of beat waves

    SciTech Connect

    Shamamian, A.H.; Gevorgian, L.A.

    1995-12-31

    An expression for the dielectric permittivity of underdense plasma interacting with laser beat waves is derived. It is shown that the presence of beat waves in plasma results in an effective growth of the plasma frequency. The FEL Gain is investigated in the case when the frequency of soft photons weakly depending on the electron beam energy and the synchronism condition is maintained. It is shown that the plasma beat waves lead to the essential increase in FEL gain.

  13. Scaling of gain with energy spread and energy in the PEP FEL

    SciTech Connect

    Fisher, A.S.

    1992-07-13

    The Sag Harbor paper on the PEP FEL discusses the scaling of various FEL parameters with energy spread {sigma}{sub {var_epsilon}}. I will repeat some of this material here and then examine the benefit of increasing the energy spread. How much energy spread can be achieved with damping wigglers is the next topic. Finally, I consider the dependence of gain and saturation length on beam energy and undulator field.

  14. Scaling of gain with energy spread and energy in the PEP FEL

    SciTech Connect

    Fisher, A.S.

    1992-07-13

    The Sag Harbor paper on the PEP FEL discusses the scaling of various FEL parameters with energy spread {sigma}{sub {var epsilon}}. I will repeat some of this material here and then examine the benefit of increasing the energy spread. How much energy spread can be achieved with damping wigglers is the next topic. Finally, I consider the dependence of gain and saturation length on beam energy and undulator field.

  15. Powerful electrostatic FEL: Regime of operation, recovery of the spent electron beam and high voltage generator

    SciTech Connect

    Boscolo, I.; Gong, J.

    1995-02-01

    FEL, driven by a Cockcroft-Walton electrostatic accelerator with the recovery of the spent electron beam, is proposed as powerful radiation source for plasma heating. The low gain and high gain regimes are compared in view of the recovery problem and the high gain regime is shown to be much more favourable. A new design of the onion Cockcroft-Walton is presented.

  16. FEL gain as a function of phace displacements induced by undulator intersection gaps

    SciTech Connect

    Varfolomeev, A.A.

    1995-12-31

    Gain characteristics are analytically considered for FEL based on a multisection undulator with short intersection gaps. It is shown that small phase displacements between laser beam and electron beam respectively caused by the above intersection gaps can seriously change the gain resonance frequency as well as gain curve shape. This effect is different from that of OK and can be used for fast undulator tuning or for its tapering. Gain characteristics are analitically considered for FEL based on a multisection undulator with short intersection gaps. It is shown that small phase displacements between laser beam and electron beam respectively caused by the above intersection gaps can seriously change the gain resonance frequency as well as gain curve shape. This effect is different from that of OK and can be used for fast undulator tuning or for its tapering.

  17. High average power CW FELs (Free Electron Laser) for application to plasma heating: Designs and experiments

    SciTech Connect

    Booske, J.H.; Granatstein, V.L.; Radack, D.J.; Antonsen, T.M. Jr.; Bidwell, S.; Carmel, Y.; Destler, W.W.; Latham, P.E.; Levush, B.; Mayergoyz, I.D.; Zhang, Z.X. . Lab. for Plasma Research); Freund, H.P. )

    1989-01-01

    A short period wiggler (period {approximately} 1 cm), sheet beam FEL has been proposed as a low-cost source of high average power (1 MW) millimeter-wave radiation for plasma heating and space-based radar applications. Recent calculation and experiments have confirmed the feasibility of this concept in such critical areas as rf wall heating, intercepted beam ( body'') current, and high voltage (0.5 - 1 MV) sheet beam generation and propagation. Results of preliminary low-gain sheet beam FEL oscillator experiments using a field emission diode and pulse line accelerator have verified that lasing occurs at the predicted FEL frequency. Measured start oscillation currents also appear consistent with theoretical estimates. Finally, we consider the possibilities of using a short-period, superconducting planar wiggler for improved beam confinement, as well as access to the high gain, strong pump Compton regime with its potential for highly efficient FEL operation.

  18. Gain length dependence on phase shake in the VUV-FEL at the TESLA Test Facility

    SciTech Connect

    Pflueger, J.; Pierini, P.

    1995-12-31

    The TTF VUV FEL, which is in its design stage at DESY, consists of a 30 m long SASE FEL which will radiate around 6 nm, driven by a superconducting linac with final energy of 1 GeV. One of the important issues in its design is the undulator performance, which is studied in this paper. The present setup, including FODO lattice, is discussed in this paper. Results of simulations, including the realistic wiggler field errors and beam stearing, are presented. Dependence of the performance, in particular the gain and saturation length as well as the saturation peak power, on the wiggler field errors is discussed.

  19. Synchronously injected amplifiers, a novel approach to high-average-power FEL

    SciTech Connect

    Nguyen, D.C.; Fortgang, C.M.; Goldstein, J.C.; Kinross-Wright, J.M.; Sheffield, R.L.

    1996-11-01

    Two new FEL ideas based on synchronously injected amplifiers are described. Both of these rely on the synchronous injection of the optical signal into a high-gain, high-efficiency tapered wiggler. The first concept, called Regenerative Amplifier FEL (RAFEL), uses an optical feedback loop to provide a coherent signal at the wiggler entrance so that the optical power can reach saturation rapidly. The second idea requires the use of a uniform wiggler in the feedback loop to generate light that can be synchronously injected back into the first wiggler. The compact Advanced FEL is being modified to implement the RAFEL concept. We describe future operation of the Advanced FEL at high average current and discuss the possibility of generating 1 kW average power.

  20. Optimization of a high brightness photoinjector for a seeded FEL facility

    NASA Astrophysics Data System (ADS)

    Penco, G.; Allaria, E.; Badano, L.; Cinquegrana, P.; Craievich, P.; Danailov, M.; Demidovich, A.; Ivanov, R.; Lutman, A.; Rumiz, L.; Sigalotti, P.; Spezzani, C.; Trovò, M.; Veronese, M.

    2013-05-01

    The FERMI@Elettra project is a seeded free electron laser (FEL) source, based on the High Gain Harmonic Generation (HGHG) scheme. It is designed to supply photons in a spectral range from 65 to 20 nm with the first undulator line (FEL-1) and from 20 nm to 4 nm with the second undulator line (FEL-2). After a first period of commissioning of the electron beam up to 100 MeV at low charge, started in August 2009, several phases of installations and beam commissioning periods have been alternated through the 2010. On December 2010 the first FEL light in the FEL-1 line was obtained at 65 nm and 43 nm by adopting as an initial seed the third harmonic of a TiSa laser. The complete optimization and commissioning of the photo-injector has been carried on in parallel with the Linac and FEL commissioning, from a conservative set-up to the final designed configuration. This paper reports the electron beam characterization in the injector area, the comparison with the theoretical expectations and the experimental process which resulted in a high brightness electron beam. This beam was optimized to be compressed and then transported through the undulators of FEL-1 where intense photons ranging from 65 nm to 20 nm were generated [1,2].

  1. Gain measurements on a waveguide FEL amplifier with pre-bunched electron beam

    SciTech Connect

    Dearden, G.; Mayhew, S.E.; Lucas, J.

    1995-12-31

    A theory proposed by Doria et al. suggests that a synchronous pre-bunched electron beam should amplify radiation with a power gain which is inversely proportional to the square root of the input power. We have measured the power gain experimentally for a waveguide FEL system using a low-voltage (55kV) pre-bunched electron beam produced by a waveguide cavity buncher. The gain has been observed as a function of the electron beam current and energy; the results are compared with theory.

  2. Coherence and linewidth studies of a 4-nm high power FEL

    NASA Astrophysics Data System (ADS)

    Fawley, W. M.; Sessler, A. M.; Scharlemann, E. T.

    1993-05-01

    Recently the SSRL/SLAC and its collaborators elsewhere have considered the merits of a 2 to 4-nm high power FEL utilizing the SLAC linac electron beam. The FEL would be a single pass amplifier excited by spontaneous emission rather than an oscillator, in order to eliminate the need for a soft X-ray resonant cavity. We have used GINGER, a multifrequency 2D FEL simulation code, to study the expected linewidth and coherence properties of the FEL, in both the exponential and saturated gain regimes. We present results concerning the effective shot noise input power and mode shape, the expected subpercent output line widths, photon flux, and the field temporal and spatial correlation functions. We also discuss the effects of tapering the wiggler upon the output power and line width.

  3. Gain narrowing of temporal and spectral widths in the UVSOR-FEL

    SciTech Connect

    Kimura, K.; Yamazaki, J.; Kinoshita, T.

    1995-12-31

    Storage ring free electron laser (SR-FEL) dynamics on the UVSOR-FEL in the visible region has been studied with measurements of the temporal and the spectral widths of the laser micropulse. The micro- and the macro-temporal structures were measured using a dual sweep streak camera. We have also investigated spectral evolution of the laser with a Fabry-Perot etalon. Only a slow sweep function of the streak camera has been used for a fringe pattern formed by the air gap etalon to derive time-dependent variations of the spectral shape. We have measured the time-averaged pulsewidths and linewidths as a function of the ring current. We observed that every macropulse contains internal substructures in both the temporal and the spectral distributions. The internal substructure, however, disappeared when the spectra of more than fifty macropulses were superimposed, and the envelope of the distribution became close to a Gaussian. We have found that the pulsewidth and the linewidth become narrower as the ring current decays. In the gain-switching mode, the micropulse duration and the linewidth at the maximum ring current were 80 ps(FWHM) and 0.3 nm(FWHM), respectively, and decreased down to 20 ps and 0.1 nm just above the threshold current. The temporal and the spectral widths seem to follow the gain behavior. Assuming that the pulsewidth and the linewidth depend on the laser gain, the bandwidth in weakly saturated situation such as SR-FEL is determined by the gain narrowing of the laser amplifier. Because the gain evolution is able to be deduced from the macropulse shape, we can obtain the relation between the bandwidth and an effective gain above the mirror loss. The temporal and the spectral evolutions of the UVSOR-FEL were well explained by the gain narrowing related to a gain integrated from the oscillation build-up to the gain saturation. Detail of the experiment and the analysis will be presented.

  4. Optimization of high average power FEL beam for EUV lithography

    NASA Astrophysics Data System (ADS)

    Endo, Akira

    2015-05-01

    Extreme Ultraviolet Lithography (EUVL) is entering into high volume manufacturing (HVM) stage, with high average power (250W) EUV source from laser produced plasma at 13.5nm. Semiconductor industry road map indicates a scaling of the source technology more than 1kW average power by high repetition rate FEL. This paper discusses on the lowest risk approach to construct a prototype based on superconducting linac and normal conducting undulator, to demonstrate a high average power 13.5nm FEL equipped with optimized optical components and solid state lasers, to study FEL application in EUV lithography.

  5. High-power FEL design issues - a critical review

    SciTech Connect

    Litvinenko, V.N.; Madey, J.M.J.; O`Shea, P.G.

    1995-12-31

    The high-average power capability of FELs has been much advertised but little realized. In this paper we provide a critical analysis of the technological and economic issues associated with high-average power FEL operation from the UV to near IR. The project of IR FEL for the Siberian Center of photochemical researches is described. The distinguished features of this project are the use of the race-track microtron-recuperator and the {open_quotes}electron output of radiation{close_quotes}. The building for the machine is under reconstruction now. About half of hardware has been manufactured. The assembly of installation began.

  6. NATIONAL HIGH MAGENTIC FIELD LABORATORY FEL INJECTOR DESIGN CONSIDERATION

    SciTech Connect

    Pavel Evtushenko; Stephen Benson; David Douglas; George Neil

    2007-06-25

    A Numerical study of beam dynamics was performed for two injector systems for the proposed National High Magnetic Field Laboratory at the Florida State University (FSU) Free Electron Laser (FEL) facility. The first considered a system consisting of a thermionic DC gun, two buncher cavities operated at 260 MHz and 1.3 GHz and two TESLA type cavities, and is very similar to the injector of the ELBE Radiation Source. The second system we studied uses a DC photogun (a copy of JLab FEL electron gun), one buncher cavity operated at 1.3 GHz and two TESLA type cavities. The study is based on PARMELA simulations and takes into account operational experience of both the JLab FEL and the Radiation Source ELBE. The simulations predict the second system will have a much smaller longitudinal emittance. For this reason the DC photo gun based injector is preferred for the proposed FSU FEL facility.

  7. Compensation of FEL gain reduction by emittance effects in a strong focusing lattice

    NASA Astrophysics Data System (ADS)

    Reiche, S.

    2000-05-01

    As the constraint of a small transverse emittance becomes more severe, the higher the electron beam energy in an FEL. To compensate for the transverse and thus the longitudinal velocity spread, a compensation scheme has been proposed previously by Derbenev and Sessler et al., for Free Electron Lasers by introducing a correlation between the energy and the average betatron amplitude of each electron. This compensation scheme is based on a constant absolute value of the transverse velocity, a feature of the natural focusing of undulators, and does not include strong focusing of a superimposed quadrupole lattice. This paper focuses on the electron motion in a strong focusing lattice with a variation in the axial velocity. The resulting reduction of the compensation efficiency is analyzed using simulations. It is seen that the compensation scheme is not much affected if the lattice cell length is shorter than the gain length. For the results presented in this paper, the parameters of the proposed TESLA X-ray FEL have been used.

  8. Application of the green function formalism to nonlinear evolution of the low gain FEL oscillator

    SciTech Connect

    Shvets, G.; Wurtele, J.S.; Gardent, D.

    1995-12-31

    A matrix formalism for the optical pulse evolution in the frequency domain, is applied to the nonlinear regime of operation. The formalism was previously developed for studies of the linear evolution of the low-gain FEL oscillator with an arbitrary shape of the electron beam. By varying experimentally controllable parameters, such as cavity detunning and cavity losses, different regimes of operation of the FEL oscillator, such as a steady state saturation and limit cycle saturation, are studied numerically. It is demonstrated that the linear supermodes, numerically obtained from the matrix formalism, provide an appropriate framework for analyzing the periodic change in the output power in the limit cycle regime. The frequency of this oscillation is related to the frequencies of the lowest-order linear supermodes. The response of the output radiation to periodic variation of the electron energy is studied. It is found that the response is enhanced when the frequency of the energy variation corresponds to the difference of per-pass phase advances of the lowest linear supermodes. Finally, various nonlinear models are tested to capture the steady state saturation and limit cycle variation of the EM field in the oscillator cavity.

  9. Status report on the development of a high-power UV/IR FEL at CEBAF

    SciTech Connect

    Benson, S.; Bohn, C.; Dylla, H.F.

    1995-12-31

    Last year we presented a design for a kilowatt industrial UV FEL based on a superconducting RF accelerator delivering 5 mA of electron-beam current at 200 MeV with energy recovery to enhance efficiency. Since then, we have progressed toward resolving several issues associated with that design. More exact simulations of the injector have resulted in a more accurate estimate of the injector performance. A new injection method has reduced the longitudinal and transverse emittance at the linac entrance. A more compact lattice has been designed for the UV FEL, and a new recirculation scheme has been identified which greatly increases the threshold for longitudinal instabilities. We decided to use a wiggler from the Advanced Photon Source which leads to a robust high-gain FEL. Analysis of the stability of an RF control system based on CEBAF control modules indicates that only minor modifications will be needed to apply them to this FEL. Detailed magnet specifications, vacuum-chamber beam apertures, and diagnostic specifications have been developed for the recirculation arcs. The design of the optical cavity has been conceptualized, and control systems have been devised to regulate mirror distortion. A half-scale model of one of the end-corner cubes has been built and tested. Finally, three-dimensional simulations have been carried out which indicate that the FEL should exceed its minimum design goals with adequate performance margin.

  10. Saturation Measurements of a Visible SASE FEL

    SciTech Connect

    Carr, Roger

    2002-08-14

    VISA (Visible to Infrared SASE Amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4 m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity.

  11. Saturation Measurements of a Visible SASE FEL

    NASA Astrophysics Data System (ADS)

    Tremaine, A.; Frigola, P.; Murokh, A.; Pellegrini, C.; Reiche, S.

    2002-08-01

    VISA (Visible to Infrared SASE Amplifier) is an FEL designed to obtain high gain at a radiation wavelength of 800 nm. Large gain is achieved by driving the FEL with the 71 MeV, high brightness beam of the Accelerator Test Facility (ATF) and using a novel, strong focusing, 4m long undulator with a gap of 6 mm and a period of 1.8 cm. We report measurements of exponential gain, saturation, and spectra of the FEL radiation intensity.

  12. High harmonic generation in undulators for FEL

    NASA Astrophysics Data System (ADS)

    Zhukovsky, K.

    2016-02-01

    The analytical study of the undulator radiation (UR), accounting for major sources of the spectral line broadening is presented. Analytical expressions for the UR spectrum and intensity are obtained. They demonstrate possibilities of the compensation of the divergency by the constant magnetic component. Some examples of single and double frequency undulators are considered. Generation of harmonics is studied with account for homogeneous and inhomogeneous broadening in real devices. The obtained results with account for all broadening sources are applied for evaluation of free electron laser (FEL) performance and compared with those, obtained with the ideal undulator.

  13. A high-average power tapered FEL amplifier at submillimeter frequencies using sheet electron beams and short-period wigglers

    SciTech Connect

    Bidwell, S.W.; Radack, D.J.; Antonsen, T.M. Jr.; Booske, J.H.; Carmel, Y.; Destler, W.W.; Granatstein, V.L.; Levush, B.; Latham, P.E.; Zhang, Z.X.

    1990-01-01

    A high-average-power FEL amplifier operating at submillimeter frequencies is under development at the University of Maryland. Program goals are to produce a CW, {approximately}1 MW, FEL amplifier source at frequencies between 280 GHz and 560 GHz. To this end, a high-gain, high-efficiency, tapered FEL amplifier using a sheet electron beam and a short-period (superconducting) wiggler has been chosen. Development of this amplifier is progressing in three stages: (1) beam propagation through a long length ({approximately}1 m) of short period ({lambda}{sub {omega}} = 1 cm) wiggler, (2) demonstration of a proof-of-principle amplifier experiment at 98 GHz, and (3) designs of a superconducting tapered FEL amplifier meeting the ultimate design goal specifications. 17 refs., 1 fig., 1 tab.

  14. A high-average-power FEL for industrial applications

    SciTech Connect

    Dylla, H.F.; Benson, S.; Bisognano, J.

    1995-12-31

    CEBAF has developed a comprehensive conceptual design of an industrial user facility based on a kilowatt UV (150-1000 nm) and IR (2-25 micron) FEL driven by a recirculating, energy-recovering 200 MeV superconducting radio-frequency (SRF) accelerator. FEL users{endash}CEBAF`s partners in the Laser Processing Consortium, including AT&T, DuPont, IBM, Northrop-Grumman, 3M, and Xerox{endash}plan to develop applications such as polymer surface processing, metals and ceramics micromachining, and metal surface processing, with the overall effort leading to later scale-up to industrial systems at 50-100 kW. Representative applications are described. The proposed high-average-power FEL overcomes limitations of conventional laser sources in available power, cost-effectiveness, tunability and pulse structure. 4 refs., 3 figs., 2 tabs.

  15. Resonator modes in high gain free electron lasers

    SciTech Connect

    Xie, Ming ); Deacon, D.A.G. ); Madey, J.M.J. . Dept. of Physics)

    1989-10-01

    When the gain in a free electron laser is high enough to produce optical guiding, the resonator mode distorts and loses its forward-backward symmetry. We show that the resonator mode in a high gain FEL can be easily constructed using the mode expansion technique taken separately in the interaction and the free-space regions. We propose design strategies to achieve maximal gain and optimal mode quality, and discuss the stability of the optimized mode. 11 refs., 4 figs.

  16. EXPERIMENTAL DEMONSTRATION OF WAVELENGTH TUNING IN HIGH-GAIN HARMONIC GENERATION FREE ELECTRON LASER.

    SciTech Connect

    SHAFTAN,T.; JOHNSON,E.; KRINSKY,S.; LOOS,H.; MURPHY,J.B.; RAKOWSKY,G.; ROSE,J.; SHEEHY,B.; SKARITKA,J.; WANG,X.J.; WU,Z.; YU,L.H.

    2004-08-29

    Tunability is one of the key aspects of any laser system. In High-Gain Harmonic Generation Free Electron Laser (HGHG FEL) the seed laser determines the output wavelength. Conventional scheme of tunable HGHG FEL requires tunable seed laser. The alternative scheme [1] is based on compression of the electron bunch with energy-time correlation (chirped bunch) in the FEL dispersive section. The chirped energy modulation, induced by the seed laser with constant wavelength, compressed as the whole bunch undergoes compression. In this paper we discuss experimental verification of the proposed approach at the DUV FEL [2,3] and compare experimental results with analytical estimates.

  17. FEL POTENTIAL OF THE HIGH CURRENT ERLs AT BNL.

    SciTech Connect

    KAYRAN,D.; BEN-ZVI, I.; LITVINENKO, V.; POZDEYEV, E.; MATVEENKO, A.; SHEVCHENKO, O.; VINOKUROV, N.

    2007-08-26

    An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL prototype will be used as a test bed to study issues relevant for very high current ERLs. High average current and high performance of electron beam with some additional components make this ERL an excellent driver for high power far infrared Free Electron Laser (FEL). A possibility for future up-grade to a two-pass ERL is considered. We present the status and our plans for construction and commissioning of the ERL. We discus a FEL potential based on electron beam provided by BNL ERL.

  18. RADIATION SPECTRUM STATISTICS IN A HIGH-GAIN FREE-ELECTRON LASER AT 266NM.

    SciTech Connect

    STAFTAN, T.; SHEEHY, B.; LOOS, H.; YU, L.H.; MURPHY, J.B.; KRINSKY, S.; ROSE, J.; WATANABE, T.; LIU, D.; WANG, X.J.

    2005-08-21

    High Gain Harmonic Generation FEL is in operations at the DUV-FEL facility (BNL). During HGHG FEL characterization we have measured a set of data demonstrating basic properties of the FEL radiation and compared them with analytic calculations [1]. This paper describes continuation of characterization of the HGHG FEL radiation output, based on the spectral measurements. We discuss analysis of an experiment at which the tunability concept of a seeded FEL with a fixed seed wavelength has been verified [2]. During the experiment we recorded about 200 radiation spectra corresponding to different energy chirps in the electron beam. We have analyzed this set of spectral data to obtain statistical properties of HGHG radiation. Correlations and trends in the radiation spectrum at 266 nm have been observed and studied.

  19. Brightness and coherence of radiation from undulators and high-gain free electron lasers

    SciTech Connect

    Kim, Kwang-Je

    1987-03-01

    The purpose of this paper is to review the radiation characteristics of undulators and high-gain free electron lasers (FELs). The topics covered are: a phase-space method in wave optics and synchrotron radiation, coherence from the phase-space point of view, discussions of undulator performances in next-generation synchrotron radiation facility and the characteristics of the high-gain FELs and their performances. (LSP)

  20. Design considerations on a high-power VUV FEL

    SciTech Connect

    Ciocci, F.; Dattoli, G.; Angelis, A. De; Garosi, F.; Giannessi, L.; Torre, A.; Faatz, B.; Ottaviani, P.L.

    1995-07-01

    The authors explore the feasibility conditions of a high-power FEL operating in the VUV region (below 100 nm) and exploiting a coupled oscillator triplicator configuration. A high quality beam from a linac is passed through a FEL oscillator and produces laser radiation at 240 nm. The same beam is extracted and then injected into a second undulator tuned at the third harmonic of the first. The bunching produced in the oscillator allows the start up of the laser signal in the second section which operates as an amplifier. The authors discuss the dynamical behavior of the system and the dependence of the output power on the characteristics of the e-beam and of the oscillator. The possibility of enhancing the output power, adding a tapered section to the second undulator, is finally analyzed.

  1. High flux and high quality FEL resonator mirrors. Final report

    SciTech Connect

    Anthony, F.M.; Mistretta, A.L.; Tonnessen, T.W.

    1989-08-01

    The Free Electron Laser Cooled Mirror Technology Development Program was highly successful; this technology can be applied to cooled silicon mirror requirements for RF linac FEL`s. Designs were developed for a 100 cm hyperboloid subjected to a peak absorbed flux of 1000 w/cm{sup 2} and for a 50 cm paraboloid with an absorbed peak flux of 500 w/cm{sup 2}. Although the design concepts were essentially the same detailed implementation was somewhat different for each of the mirrors. Both designs incorporated variable geometry and internal flow tailoring over the planform area so as to produce a near spherical distortion response to the input Gaussian power distribution. This enhanced correctability of the overall distortion such that the net distortion was only 0.2 A/(w/cm{sup 2}) after correction for sphere, piston and bit as compared to a design goal of 0.5 A/(w/cm{sup 2}). Structural integrity testing of small samples, that incorporated internal geometries of both types of mirrors, verified the adequacy of the designs. Fabrication of the different types of test specimens demonstrated the producibility of the configurations. Planform bonding of manifold simulations was successful; they type of bonding is required to produce a 50 cm diameter circular silicon mirror from boules that are somewhat smaller in diameter. After planform bonding of preforms they were machined, etched, assembled into pressure test specimens, and burst pressure tested. The average burst pressure of 1550 psig was somewhat stronger than early SHOP specimens of the same configuration but somewhat lower than more recently produced specimens which evidenced burst pressure strengths of 2500 psig. Demonstrated planform bond strengths are more than adequate for the mirrors of interest, better performance can be expected as the bonding precess is refined. These, and the other experimental results indicate the large factor of safety provided by the designs.

  2. Undulator interruption in high-gain free electron lasers

    SciTech Connect

    Kim, K.J.

    1997-10-01

    The effect of interrupting an undulator on the performance of high-gain free-electron lasers (FELs) is evaluated by analyzing 1-D Maxwell-Vlasov equations. It is found that the effect is small for a reasonable length of the interruptions for FEL parameters envisaged for short wavelength self-amplified spontaneous emission (SASE). Since the interruptions provide valuable space for quadrupoles and diagnostics, and at the same time permit a greater flexibility in mechanical design, the result of this paper is encouraging for construction of long undulator magnets required for SASE.

  3. Lightning control system using high power microwave FEL

    SciTech Connect

    Shiho, M.; Watanbe, A.; Kawasaki, S.

    1995-12-31

    A research project for developing a thunder lightning control system using an induction linac based high power microwave free electron laser (FEL) started at JAERI The system will produce weakly ionized plasma rod in the atmosphere by high power microwaves and control a lightning path, away from , e. g., nuclear power stations and rocket launchers. It has been known that about MW/cm{sup 2} power density is enough for the atmospheric breakdown in the microwave region, and which means high power microwave FEL with GW level output power is feasible for atmospheric breakdown, and accordingly is feasible for thunder lightning control tool with making a conductive plasma channel in the atmosphere. From the microwave attenuation consideration in the atmosphere, FEL of 35GHz(0.13dB/km), 90GHz(0.35dB/km), 140GHz(1.7dB/km), and of 270 GHz(4.5dB/km) are the best candidates for the system. Comparing with other proposed lightning control system using visible or ultraviolet laser, the system using microwave has an advantage that microwave suffers smaller attenuation by rain or snow which always exist in the real atmospheric circumstances when lightning occurs.

  4. Energy stability in a high average power FEL

    SciTech Connect

    Mermings, L.; Bisognano, J.; Delayen, J.

    1995-12-31

    Recirculating, energy-recovering linacs can be used as driver accelerators for high power FELs. Instabilities which arise from fluctuations of the cavity fields or beam current are investigated. Energy changes can cause beam loss on apertures, or, when coupled to M, phase oscillations. Both effects change the beam induced voltage in the cavities and can lead to unstable variations of the accelerating field. Stability analysis for small perturbations from equilibrium is performed and threshold currents are determined. Furthermore, the analytical model is extended to include feedback. Comparison with simulation results derived from direct integration of the equations of motion is presented. Design strategies to increase the instability threshold are discussed and the UV Demo FEL, proposed for construction at CEBAF, and the INP Recuperatron at Novosibirsk are used as examples.

  5. Collapsible high gain antenna

    NASA Technical Reports Server (NTRS)

    Cribb, H. E. (Inventor)

    1973-01-01

    A lightweight small high gain antenna which is capable of being packaged in a collapsed form and automatically expanded when in use is described. The antenna includes a cylindrical housing having a rod with a piston adjacent to one end extending through it. Attached to the outer end of the rod in a normally collapsed state is a helical wire coil. When the gas producing means is activated the piston and rod are shifted outwardly to expand the wire coil. A latch is provided for holding the helical coil in the expanded position.

  6. Helicopter high gain control

    NASA Technical Reports Server (NTRS)

    Cunningham, T. B.; Nunn, E. C.

    1979-01-01

    High gain control is explored through a design study of the CH-47B helicopter. The plans are designed to obtain the maximum bandwidth possible given the hardware constraints. Controls are designed with modal control theory to specific bandwidths and closed loop mode shapes. Comparisons are made to an earlier complementary filter approach. Bandwidth improvement by removal of limitations is explored in order to establish hardware and mechanization options. Improvements in the pitch axis control system and in the rate gyro sensor noise characteristics in all axes are discussed. The use of rotor state feedback is assessed.

  7. Three-Dimensional Analysis of Frequency-Chirped FELs

    SciTech Connect

    Huang, Z.; Ding, Y.; Wu, J.; /SLAC

    2010-09-14

    Frequency-chirped free-electron lasers (FELs) are useful to generate a large photon bandwidth or a shorter x-ray pulse duration. In this paper, we present a three-dimensional analysis of a high-gain FEL driven by the energy-chirped electron beam. We show that the FEL eigenmode equation is the same for a frequency-chirped FEL as for an undulator-tapered FEL. We study the transverse effects of such FELs including mode properties and transverse coherence.

  8. Eigenmode analysis of a high-gain free-electron laser based on a transverse gradient undulator

    NASA Astrophysics Data System (ADS)

    Baxevanis, Panagiotis; Huang, Zhirong; Ruth, Ronald; Schroeder, Carl B.

    2015-01-01

    The use of a transverse gradient undulator (TGU) is viewed as an attractive option for free-electron lasers (FELs) driven by beams with a large energy spread. By suitably dispersing the electron beam and tilting the undulator poles, the energy spread effect can be substantially mitigated. However, adding the dispersion typically leads to electron beams with large aspect ratios. As a result, the presence of higher-order modes in the FEL radiation can become significant. To investigate this effect, we study the eigenmode properties of a TGU-based, high-gain FEL, using both an analytically-solvable model and a variational technique. Our analysis, which includes the fundamental and the higher-order FEL eigenmodes, can provide an estimate of the mode content for the output radiation. This formalism also enables us to study the trade-off between FEL gain and transverse coherence. Numerical results are presented for a representative soft X-ray, TGU FEL example.

  9. Multi-level quantum electrodynamic calculation of spontaneous emission and small signal gain in high voltage free electron lasers

    NASA Astrophysics Data System (ADS)

    Chang, C. S.; Fluhler, H. U.

    1991-12-01

    Using the Weisskopf-Wigner technique, a self consistent quantum electrodynamic (SCQED) theory of spontaneous emission of radiation and single photon small signal gain is developed for high voltage free electron lasers (FEL). Excellent agreement is obtained simultaneously to our knowledge for the first time between the predictions and the experimental observations for lineshift, linewidth and gain. The SCQED theory predicts lineshift and broadening due to quantum mechanical effects for linear, helical and tapered undulator FELs which are not predicted by the classical/conventional FEL theories, but which have been observed 4,5,18,22,23,45,46. Excellent agreement is obtained between the SCQED theory predicted spontaneous emission spectra and the 1980?81 ACO FEL4,18, ACO Optical Klystron FEL45,46, Stanford 10.6 ?m FEL22 and Stanford 3.4 ?m FEL23 experimental spectra. This agreement is much better than the prediction from the classical/conventional FEL theory which gives errors of many tens of percent. We show that the spontaneous emission spectrum obtained from classical/conventional FEL theories is valid only in the limit of a short undulator containing a small number of periods. The small signal gain derived from the SCQED theory is shown to reduce to Colson's gain formula12,34 in the classical limit. However, the SCQED theory predicts significant reductions in the small signal gain which agree well with the ACO gain data5, and are not predicted well by Colson's formula. Due to the non-neglible finite electron state lifetime, it is discovered that a fundamental physical gain limit exists which is universal to all types of FELs within the limits of the single photon transition scheme considered (i.e. if multiphoton effects are ignored). Finally, the implications of the theoretically obtained results are discussed for practical conditions of experimental interest. It is shown that under practical experimental conditions quantum effects can be quite important in the

  10. Multicolor High-Gain Free-Electron Laser Driven by Seeded Microbunching Instability.

    PubMed

    Roussel, E; Ferrari, E; Allaria, E; Penco, G; Di Mitri, S; Veronese, M; Danailov, M; Gauthier, D; Giannessi, L

    2015-11-20

    Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. Here, we demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL. PMID:26636852

  11. Multicolor High-Gain Free-Electron Laser Driven by Seeded Microbunching Instability

    NASA Astrophysics Data System (ADS)

    Roussel, E.; Ferrari, E.; Allaria, E.; Penco, G.; Di Mitri, S.; Veronese, M.; Danailov, M.; Gauthier, D.; Giannessi, L.

    2015-11-01

    Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. Here, we demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL.

  12. High flux and high quality FEL resonator mirrors

    SciTech Connect

    Anthony, F.M.; Mistretta, A.L.; Tonnessen, T.W. )

    1989-08-01

    The Free Electron Laser Cooled Mirror Technology Development Program was highly successful; this technology can be applied to cooled silicon mirror requirements for RF linac FEL's. Designs were developed for a 100 cm hyperboloid subjected to a peak absorbed flux of 1000 w/cm[sup 2] and for a 50 cm paraboloid with an absorbed peak flux of 500 w/cm[sup 2]. Although the design concepts were essentially the same detailed implementation was somewhat different for each of the mirrors. Both designs incorporated variable geometry and internal flow tailoring over the planform area so as to produce a near spherical distortion response to the input Gaussian power distribution. This enhanced correctability of the overall distortion such that the net distortion was only 0.2 A/(w/cm[sup 2]) after correction for sphere, piston and bit as compared to a design goal of 0.5 A/(w/cm[sup 2]). Structural integrity testing of small samples, that incorporated internal geometries of both types of mirrors, verified the adequacy of the designs. Fabrication of the different types of test specimens demonstrated the producibility of the configurations. Planform bonding of manifold simulations was successful; they type of bonding is required to produce a 50 cm diameter circular silicon mirror from boules that are somewhat smaller in diameter. After planform bonding of preforms they were machined, etched, assembled into pressure test specimens, and burst pressure tested. The average burst pressure of 1550 psig was somewhat stronger than early SHOP specimens of the same configuration but somewhat lower than more recently produced specimens which evidenced burst pressure strengths of 2500 psig. Demonstrated planform bond strengths are more than adequate for the mirrors of interest, better performance can be expected as the bonding precess is refined. These, and the other experimental results indicate the large factor of safety provided by the designs.

  13. Development of a high average power, CW, MM-wave FEL

    SciTech Connect

    Ramian, G.

    1995-12-31

    Important operational attributes of FELs remain to be demonstrated including high average power and single-frequency, extremely narrow-linewidth lasing. An FEL specifically designed to achieve these goals for scientific research applications is currently under construction. Its most salient feature is operation in a continuous-wave (CW) mode with an electrostatically generated, high-current, recirculating, DC electron beam.

  14. High Power Operation of the JLab IR FEL Driver Accelerator

    SciTech Connect

    Kevin Beard; Stephen Benson; George Biallas; James Boyce; Donald Bullard; James Coleman; David Douglas; H. Dylla; Richard Evans; Pavel Evtushenko; Christopher Gould; Albert Grippo; Joseph Gubeli; David Hardy; Carlos Hernandez-Garcia; J. Hovater; Kevin Jordan; John Klopf; Rui Li; Steven Moore; George Neil; Benard Poelker; Thomas Powers; Joseph Preble; Robert Rimmer; Daniel Sexton; Michelle D. Shinn; Christopher Tennant; Richard Walker; Gwyn Williams; Shukui Zhang

    2007-08-01

    Operation of the JLab IR Upgrade FEL at CW powers in excess of 10 kW requires sustained production of high electron beam powers by the driver ERL. This in turn demands attention to numerous issues and effects, including: cathode lifetime; control of beamline and RF system vacuum during high current operation; longitudinal space charge; longitudinal and transverse matching of irregular/large volume phase space distributions; halo management; management of remnant dispersive effects; resistive wall, wake-field, and RF heating of beam vacuum chambers; the beam break up instability; the impact of coherent synchrotron radiation (both on beam quality and the performance of laser optics); magnetic component stability and reproducibility; and RF stability and reproducibility. We discuss our experience with these issues and describe the modus vivendi that has evolved during prolonged high current, high power beam and laser operation.

  15. HIGH GAIN HARMONIC GENERATION UV TO DUV FREE ELECTRON LASERS AT THE NSLS.

    SciTech Connect

    WU, J.; YU, L.H.

    2001-06-18

    In this paper, we present the calculation on the performance of High Gain Harmonic Generation (HGHG) UV to DUV Free Electron Lasers (FELs) at the NSLS. Based on the beam quality and the available undulators at the NSLS, the calculation shows that it is possible to produce fully coherent DUV FEL down to 500 Angstrom, with a peak power of several hundred Mega Watts. One further attractive feature is the possibility to produce ultra short radiation pulse based on such HGHG scheme.

  16. Interplay of the Chirps and Chirped Pulse Compression in a High-gain Seeded Free-electron Laser

    SciTech Connect

    Wu, Juhao; Murphy, J.B.; Emma, P.J.; Wang, X.J.; Watanabe, T.; Zhong, Xinming; /Beijing Normal U.

    2007-01-03

    In a seeded high-gain Free-electron Laser (FEL), where a coherent laser pulse interacts with an ultra-relativistic electron beam, the seed laser pulse can be frequency chirped, and the electron beam can be energy chirped. Besides these two chirps, the FEL interaction introduces an intrinsic frequency chirp in the FEL even if the above mentioned two chirps are absent. In this paper we examine the interplay of these three chirps. The problem is formulated as an initial value problem, and solved via a Green function approach. Besides the chirp evolution, we also give analytical expressions for the pulse duration and bandwidth of the FEL, which remains fully longitudinally coherent in the high gain exponential growth regime. Because the chirps are normally introduced for a final compression of the FEL pulse, some conceptual issues are discussed. We show that in order to get a short pulse duration, an energy chirp in the electron beam is necessary.

  17. Towards short wavelengths FELs workshop

    SciTech Connect

    Ben-Zvi, I.; Winick, H.

    1993-12-01

    This workshop was caged because of the growing perception in the FEL source community that recent advances have made it possible to extend FEL operation to wavelengths about two orders of magnitude shorter than the 240 nm that has been achieved to date. In addition short wavelength FELs offer the possibilities of extremely high peak power (several gigawatts) and very short pulses (of the order of 100 fs). Several groups in the USA are developing plans for such short wavelength FEL facilities. However, reviewers of these plans have pointed out that it would be highly desirable to first carry out proof-of-principle experiments at longer wavelengths to increase confidence that the shorter wavelength devices will indeed perform as calculated. The need for such experiments has now been broadly accepted by the FEL community. Such experiments were the main focus of this workshop as described in the following objectives distributed to attendees: (1) Define measurements needed to gain confidence that short wavelength FELs will perform as calculated. (2) List possible hardware that could be used to carry out these measurements in the near term. (3) Define a prioritized FEL physics experimental program and suggested timetable. (4) Form collaborative teams to carry out this program.

  18. A pure permanent magnet-two plane focusing-tapered wiggler for a high average power FEL

    SciTech Connect

    Fortgang, C.M.

    1996-11-01

    A high-average power FEL is under construction at Los Alamos. The FEL will have aspects of both an oscillator and a SASE (self-amplified spontaneous emission) device. That is, a high-gain and high- extraction efficiency wiggler will be used with a very low-Q optical resonator. FEL simulations reveal that a tapered wiggler with two- plane focusing is required to obtain desired performance. The wiggler is comprised of a I meter long untapered section followed by a 1 meter tapered section. The taper is achieved with the magnetic gap and not the wiggler period which is constant at 2 cm. The gap is tapered from 5.9 mm to 8.8 mm. The, gap, rather than the period, is tapered to avoid vignetting of the 16 {mu}m optical beam. Two-plane focusing is necessary to maintain high current density and thus high gain through out the 2 meter long wiggler. Several magnetic designs have been considered for the wiggler. The leading candidate approach is a pure permanent wiggler with pole faces that are cut to roughly approximate the classical parabolic pole face design. Focusing is provided by the sextupole component of the wiggler magnetic field and is often called ``natural`` or ``betatron`` focusing. Details of the design will be presented.

  19. Operating synchrotron light sources with a high gain free electron laser

    NASA Astrophysics Data System (ADS)

    Di Mitri, S.; Cornacchia, M.

    2015-11-01

    Since the 1980s synchrotron light sources have been considered as drivers of a high repetition rate (RR), high gain free electron laser (FEL) inserted in a by-pass line or in the ring itself. As of today, the high peak current required by the laser is not deemed to be compatible with the standard multi-bunch filling pattern of synchrotrons, and in particular with the operation of insertion device (ID) beamlines. We show that this problem can be overcome by virtue of magnetic bunch length compression in a ring section, and that, after lasing, the beam returns to equilibrium conditions without beam quality disruption. Bunch length compression brings a double advantage: the high peak current stimulates a high gain FEL emission, while the large energy spread makes the beam less sensitive to the FEL heating and to the microwave instability in the ring. The beam’s large energy spread at the undulator is matched to the FEL energy bandwidth through a transverse gradient undulator. Feasibility of lasing at 25 nm is shown for the Elettra synchrotron light source at 1 GeV, and scaling to shorter wavelengths as a function of momentum compaction, beam energy and transverse emittance in higher energy, larger rings is discussed. For the Elettra case study, a low (100 Hz) and a high (463 kHz) FEL RR are considered, corresponding to an average FEL output power at the level of ∼1 W (∼1013 photons per pulse) and ∼300 W (∼1011 photons per pulse), respectively. We also find that, as a by-product of compression, the ∼5 W Renieri’s limit on the average FEL power can be overcome. Our conclusion is that existing and planned synchrotron light sources may be made compatible with this new hybrid IDs-plus-FEL operational mode, with little impact on the standard beamlines functionality.

  20. Lasing with a Near-Confocal cavity in a high power FEL

    SciTech Connect

    Stephen Benson; George Neil; Michelle D. Shinn

    2002-01-01

    Lasing at high power in FELs has been achieved so far only with a near-concentric resonator [1]. Though this design can scale up to quite high power, it is ultimately limited by the mirror steering stability as the resonator design approaches concentricity. This constraint may be avoided by using a near-confocal resonator operated in a ring configuration. It is found that, if a small amount of gain focusing is present, the near-confocal resonator eigenmodes are modified such that the lowest order mode collapses around the electron beam and is large in the return (non-focusing) direction. This eigenmode is stable and is relatively insensitive to changes in the mirror radii of curvature and the strength of the electron beam focusing. This paper will present the theory of this new concept.

  1. High quality hybrid wiggler for infrared FEL and coherent harmonic generation

    NASA Astrophysics Data System (ADS)

    Stolovy, G.; Wadensweiler, W.; Madey, J. M. J.; Benson, S.; Velghe, M.

    1986-05-01

    A compact hybrid undulator, the Stanford IRFEL, employing both SmCo permanent magnets and Vanadium Permendur steel poles, is shown to be a cost-effective structure for FELs requiring high peak magnetic fields. The hybrid IRFEL allows the on-axis magnetic fields to be adjusted with high precision, and the capability of remagnetizing individual magnets enables methodical gap-independent corrections. Experiments with the laser saturated demonstrated that the seventh harmonic of 3.1 microns in the blue was clearly visible, and a net gain at this wavelength of 28 percent, consistent with simulations assuming an ideal wiggler of 47 periods, is shown. The gap-dependent steering was measured to be + or - 0.5 mrad, and tuning is possible with only slight adjustments to the initial beam steering.

  2. Status of the project of Novosibirsk high power FEL

    SciTech Connect

    Pinayev, I.V.; Erg, G.I.; Gavrilov, N.G.

    1995-12-31

    The project of IR FEL for the Siberian Center of photochemical researches is described. The distinguished features of this project are the use of the race-track microtron-recuperator and the {open_quotes}electron output of radiation{close_quotes}. The building for the machine is under reconstruction now. About half of hardware has been manufactured. The assembly of installation began.

  3. Prospects for a soft x-ray FEL powered by a relativistic-klystron high-gradient accelerator (RK-HGA)

    SciTech Connect

    Shay, H.D.; Barletta, W.A.; Yu, S.S.; Schlueter, R.; Deis, G.A.

    1989-09-28

    We present here the concept of x-ray FELs using high gain, single-pass amplifiers with electron beams accelerated in high gradient structures powered by relativistic klystrons. Other authors have also considered x-ray FELs; the unique aspect of this paper is the use of high gradient acceleration. One of the authors has previously presented preliminary studies on this concept. The intent in this paper is to display the results of a top level design study on a high gain FEL, to present its sensitivity to a variety of fabrication and tuning errors, to discuss several mechanisms for increasing gain yet more, and to present explicitly the output characteristics of such an FEL. The philosophy of the design study is to find a plausible operating point which employs existing or nearly existing state-of-the-art technologies while minimizing the accelerator and wiggler lengths. The notion is to distribute the technical risk as evenly as possible over the several technologies so that each must advance only slightly in order to make this design feasible. This study entailed no systematic investigation of possible costs so that, for example, the sole criterion for balancing the trade-off between beam energy and wiggler length is that the two components have comparable lengths. 20 refs., 10 figs., 1 tab.

  4. Measuring FEL Radiation Properties at VISA-FEL

    SciTech Connect

    Cornacchia, Massimo

    2002-08-21

    The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements.

  5. DC High Voltage Conditioning of Photoemission Guns at Jefferson Lab FEL

    NASA Astrophysics Data System (ADS)

    Hernandez-Garcia, C.; Benson, S. V.; Biallas, G.; Bullard, D.; Evtushenko, P.; Jordan, K.; Klopf, M.; Sexton, D.; Tennant, C.; Walker, R.; Williams, G.

    2009-08-01

    DC high voltage photoemission electron guns with GaAs photocathodes have been used to produce polarized electron beams for nuclear physics experiments for about 3 decades with great success. In the late 1990s, Jefferson Lab adopted this gun technology for a free electron laser (FEL), but to assist with high bunch charge operation, considerably higher bias voltage is required compared to the photoguns used at the Jefferson Lab Continuous Electron Beam Accelerator Facility. The FEL gun has been conditioned above 400 kV several times, albeit encountering non-trivial challenges with ceramic insulators and field emission from electrodes. Recently, high voltage processing with krypton gas was employed to process very stubborn field emitters. This work presents a summary of the high voltage techniques used to high voltage condition the Jefferson Lab FEL photoemission gun.

  6. Strategies for minimizing emittance growth in high charge CW FEL injectors

    SciTech Connect

    Liu, H.

    1995-12-31

    This paper is concerned with the best strategies for designing low emittance, high charge CW FEL injectors. This issue has become more and more critical as today`s interest in FELs is toward UV wavelength high average power operation. The challenge of obtaining the smallest possible emittance is discussed from both the practical point of view and the beam physics point of view. Various mechanisms responsible for beam emittance growth are addressed in detail. Finally, the design of a high charge injector test stand at CEBAF is chosen to help illustrate the design strategies and emittance growth mechanisms discussed in this paper.

  7. FEL-based coherent electron cooling for high-energy hadron colliders

    SciTech Connect

    Litvinenko,V.N.; Derbenev, Y.S.

    2008-06-23

    Cooling intense high-energy hadron beams is a major challenge in modern accelerator physics. Synchrotron radiation is too feeble and two common methods--stochastic and electron cooling--are not efficient in providing significant cooling for high energy, high intensity proton colliders. In this paper they discuss a practical scheme of Coherent Electron Cooling (CeC), which promises short cooling times (below one hour) for intense proton beams in RHIC at 250 GeV or in LHC at 7 TeV. A possibility of CeC using various microwave instabilities was discussed since 1980s. In this paper, they present first evaluation of specific CeC scheme based on capabilities of present-day accelerator technology, ERLs, and high-gain Free-Electron lasers (FELs). They discuss the principles, the main limitations of this scheme and present some predictions for Coherent Electron Cooling in RHIC and the LHC operating with ions or protons, summarized in Table 1.

  8. A Dynamic Feedback Model for High Repetition Rate LINAC-Driven FELS

    SciTech Connect

    Mellado Munoz, M.; Doolittle, L.; Emma, P.; Huang, G.; Ratti, A.; Serrano, C.; Byrd, J. M.

    2012-05-20

    One of the concepts for the next generation of linacdriven FELs is a CW superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the stability of the xray pulses by improving the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. A high repetition rate FEL with a CW linac presents an opportunity to use a variety of broadband feedbacks to stabilize the beam parameters. To understand the performance of such a feedback system, we are developing a dynamic model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and includes the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we present a detailed description of this model.

  9. A Design Study of a FIR/THz-FEL for High Magnetic Field Research

    SciTech Connect

    Tecimer, M; Brunel, L C; Tol, J van; Neil, G

    2006-09-01

    Presently a conceptual design work for a NIR-FIR FEL system at the NHMFL/FSU is being undertaken. The system is intended to combine high magnetic field research with an intense, tuneable photon source, spanning the spectral region ~2–1000 microns. Here, we present a design study involving the FIR/THz part of the NHMFL FEL design proposal. The suggested long-wavelength FEL encompasses in the first phase a thermionic injector (similar to that in use at the Forschungszentrum-Rossendorf ELBE facility) with a planned ~2 mA average current and a ~10 MeV superconducting rf linac module operating at 1.3 GHz. The broadband outcoupling over the envisaged FIR/THz spectral range (100–1100 microns) is accomplished by adopting a single (variable height slot) outcoupler in a waveguided cavity. Besides the performance predictions of the suggested long-wavelength FEL, techniques for the generation of high peak power, nanoseconds long THz pulses (for magnetic resonance applications) are also reported.

  10. First Lasing of the Regenerative Amplifier FEL

    SciTech Connect

    Nguyen, D.C.; Sheffield, R.L.; Fortang, C.M.; Goldstein, J.C.; Kinross-Wright, J.M.; Ebrahim, N.A.

    1998-08-17

    The Regenerative Amplifier Free-Electron Laser (RAFEL) is a high-gain RF-linac FEL capable of producing high optical power from a compact design. The combination of a high-gain and small optical feedback enables the FEL to reach saturation and produce a high optical power and high extraction efficiency without risk of optical damage to the mirrors. This paper summarizes the first lasing of the Regenerative Amplifier FEL and describes recent experimental results. The highest optical energy achieved thus far at 16.3 {micro}m is 1.7 J over an 9-{micro}s macropulse, corresponding to an average power during the macropulse of 190 kW. They deduce an energy of 1.7 mJ in each 16 ps micropulse, corresponding to a peak power of 110 MW.

  11. Characterization of an 800 nm SASE FEL at Saturation

    SciTech Connect

    Nuhn, Heinz-Dieter

    2002-11-13

    VISA (Visible to Infrared SASE Amplifier) is an FEL (Free Electron Laser) designed to saturate at a radiation wavelength of 800 nm within a 4-m long, strong focusing undulator. Large gain is achieved by driving the FEL with the 72 MeV, high brightness beam of BNL's Accelerator Test Facility (ATF). We present measurements that demonstrate saturation in addition to the frequency spectrum of the FEL radiation. Energy, gain length and spectral characteristics are compared and shown to agree with simulation and theoretical predictions.

  12. Los Alamos High-Brightness Accelerator FEL (HIBAF) facility

    SciTech Connect

    Cornelius, W.D.; Bender, S.; Meier, K.; Thode, L.E.; Watson, J.M.

    1989-01-01

    The 10-/mu/m Los Alamos free-electron laser (FEL) facility is being upgraded. The conventional electron gun and bunchers have been replaced with a much more compact 6-MeV photoinjector accelerator. By adding existing parts from previous experiments, the primary beam energy will be doubled to 40 MeV. With the existing 1-m wiggler (/lambda//sub w/ = 2.7 cm) and resonator, the facility can produce photons with wavelengths from 3 to 100 /mu/m when lasing on the fundamental mode and produce photons in the visible spectrum with short-period wigglers or harmonic operation. After installation of a 150/degree/ bend, a second wiggler will be added as an amplifier. The installation of laser transport tubes between the accelerator vault and an upstairs laboratory will provide experimenters with a radiation-free environment for experiments. Although the initial experimental program of the upgraded facility will be to test the single accelerator-master oscillator/power amplifier configuration, some portion of the operational time of the facility can be dedicated to user experiments. 13 refs., 5 figs., 6 tabs.

  13. Normal conducting RF cavity of high current photoinjector for high power CW FEL.

    SciTech Connect

    Kurennoy, S.; Schrage, D. L.; Wood R. L.; Schultheiss, T.; Rathke, J.; Christina, V.; Young, L. M.

    2004-01-01

    An RF photoinjector capable of producing high continuous average current with low emittance and energy spread is a key enabling technology for high power CW FEL. The design of a 2.5-cell {pi}-mode 700-MHz normal-conducting RF photoinjector cavity with magnetic emittance compensation is completed. With the electric field gradients of 7, 7, and 5 MV/m in the three cells, the photoinjector will produce a 2.5-MeV electron beam with 3-nC charge per bunch and 7 mm-mrad transverse rms emittance. Electromagnetic modeling was used extensively to optimize ridge-loaded tapered waveguides and RF couplers, which led to a new improved coupler-iris design. The results, combined with a thermal/stress analysis, show that the challenging problem of cavity cooling can be successfully solved. A demo 100-mA (at 35-MHz bunch-repetition rate) photoinjector is being manufactured. The design is scalable to higher power levels by increasing the bunch repetition rate, and provides a path to a MW-class amplifier FEL. The cavity design and details of RF coupler modeling are presented.

  14. Normal-conducting RF cavity of high current photoinjector for high power CW FEL.

    SciTech Connect

    Kurennoy, S.; Schrage, D. L.; Wood R. L.; Schultheiss, T.; Rathke, J.; Young, L. M.

    2004-01-01

    An RF photoinjector capable of producing high continuous average current with low emittance and energy spread is a key enabling technology for high power CW FEL. The design of a 2.5-cell, {pi}-mode, 700-MHz normal-conducting RF photoinjector cavity with magnetic emittance compensation is completed. With the electric field gradients of 7.7, and 5 MV/m in the three cells, the photoinjector will produce a 2.5-MeV electron beam with 3-nC charge per bunch and the transverse rms emittance 7 mm-mrad. Electromagnetic modeling was used extensively to optimize ridge-loaded tapered waveguides and RF couplers, which led to a new, improved coupler iris design. The results, combined with a thermal and stress analysis, show that the challenging problem of cavity cooling can be successfully solved. The manufacturing of a demo 100-mA (at 35 MHz bunch repetition rate) photoinjector is underway. The design is scalable to higher power levels by increasing the electron bunch repetition rate, and provides a path to a MW-class amplifier FEL. This paper presents the cavity design and details of RF coupler modeling.

  15. Seeded FEL Microbunching Experiments at the UCLA Neptune Laboratory

    SciTech Connect

    Tochitsky, S. Ya.; Musumeci, P.; Rosenzweig, J. B.; Joshi, C.; Gottschalk, S. C.

    2010-11-04

    Seeded high-gain FELs, which can generate very powerful radiation pulses in a relatively compact undulator and simultaneously modulate the electron beam longitudinally at the seed wavelength, are important tools for advanced accelerator development. A single-pass 0.5-9 THz FEL amplifier-buncher driven by a regular photoinjector is being built at the UCLA Neptune Laboratory. FEL interactions at 340 {mu}m (1 THz) are considered for the first experiment, since time-resolved measurements of longitudinal current distribution of the bunched beam using the RF deflecting cavity are possible. A design of a 0.2-2.0 {mu}m FEL using the same undulators is presented. In this case the FEL is driven by a high-peak current beam from the laser-plasma accelerator tunable in the 100-300 MeV range.

  16. High current gain transistor laser.

    PubMed

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-01-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge. PMID:27282466

  17. High current gain transistor laser

    NASA Astrophysics Data System (ADS)

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-06-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge.

  18. High current gain transistor laser

    PubMed Central

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-01-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge. PMID:27282466

  19. Longitudinal Coherence Preservation and Chirp Evolution in a High Gain Laser Seeded Free Electron Laser Amplifier

    SciTech Connect

    Murphy, J.B.; Wu, Juhao; Wang, X.J.; Watanabe, T.; /BNL, NSLS

    2006-06-07

    In this letter we examine the start-up of a high gain free electron laser in which a frequency-chirped coherent seed laser pulse interacts with a relativistic electron beam. A Green function formalism is used to evaluate the initial value problem. We have fully characterized the startup and evolution through the exponential growth regime. We obtain explicit expressions for the pulse duration, bandwidth and chirp of the amplified light and show that the FEL light remains fully longitudinally coherent.

  20. Design Studies for a High-Repetition-Rate FEL Facility at LBNL.

    SciTech Connect

    CORLETT, J.; BELKACEM, A.; BYRD, J. M.; FAWLEY, W.; KIRZ, J.; LIDIA, S.; MCCURDY, W.; PADMORE, H.; PENN, G.; POGORELOV, I.; QIANG, J.; ROBIN, D.; SANNIBALE, F.; SCHOENLEIN, R.; STAPLES, J.; STEIER, C.; VENTURINI, M.; WAN, W.; WILCOX, R.; ZHOLENTS, A.

    2007-10-04

    Lawrence Berkeley National Laboratory (LBNL) is working to address the needs of the primary scientific Grand Challenges now being considered by the U.S. Department of Energy, Office of Basic Energy Sciences: we are exploring scientific discovery opportunities, and new areas of science, to be unlocked with the use of advanced photon sources. A partnership of several divisions at LBNL is working to define the science and instruments needed in the future. To meet these needs, we propose a seeded, high-repetition-rate, free-electron laser (FEL) facility. Temporally and spatially coherent photon pulses, of controlled duration ranging from picosecond to sub-femtosecond, are within reach in the vacuum ultraviolet (VUV) to soft X-ray regime, and LBNL is developing critical accelerator physics and technologies toward this goal. We envision a facility with an array of FELs, each independently configurable and tunable, providing a range of photon-beam properties with high average and peak flux and brightness.

  1. Results of the VISA SASE FEL Experiment at 840 nm

    SciTech Connect

    Murokh, A.

    2004-01-20

    VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission FEL, which achieved saturation at 840 nm within a single-pass 4-m undulator. A gain length shorter than 18 cm has been obtained, yielding the gain of 2 x 10{sup 8} at saturation. The FEL performance, including spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. The results are compared to 3-D SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL system. Detailed agreement between simulations and experimental results is obtained over the wide range of the electron beam parameters.

  2. Results of the VISA SASE FEL experiment at 840 nm

    NASA Astrophysics Data System (ADS)

    Murokh, A.; Agustsson, R.; Babzien, M.; Ben-Zvi, I.; Bertolini, L.; van Bibber, K.; Carr, R.; Cornacchia, M.; Frigola, P.; Hill, J.; Johnson, E.; Klaisner, L.; Le Sage, G.; Libkind, M.; Malone, R.; Nuhn, H.-D.; Pellegrini, C.; Reiche, S.; Rakowsky, G.; Rosenzweig, J.; Ruland, R.; Skaritka, J.; Toor, A.; Tremaine, A.; Wang, X.; Yakimenko, V.

    2003-07-01

    VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission FEL, which achieved saturation at 840 nm within a single-pass 4-m undulator. A gain length shorter than 18 cm has been obtained, yielding the gain of 2×10 8 at saturation. The FEL performance, including spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. The results are compared to 3-D SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL system. Detailed agreement between simulations and experimental results is obtained over the wide range of the electron beam parameters.

  3. Saturation and pulsed FEL dynamics

    SciTech Connect

    Giannessi, L.; Mezi, L.

    1995-12-31

    The behavior of a FEL operating in the saturated pulsed regime, may be reproduced by the linear FEL integral equation, suitably modified to include saturation effects through a gain depression coefficient depending on the laser intensity. This simple method allows to evaluate several FEL parameters like gain, efficiency, band-width and optical pulse duration as functions of the optical cavity length, only with a numerical integration. The predictions have been compared with available experimental and numerical data, and the method has been applied to estimate the operating characteristics of some planned FEL experiments.

  4. JLab High-Current CW Cryomodules for ERL and FEL Applications

    SciTech Connect

    Robert Rimmer; Richard Bundy; Guangfeng Cheng; Gianluigi Ciovati; Edward Daly; Richard Getz; William Hicks; James Henry; Peter Kneisel; Stephen Manning; Robert Manus; Karl Smith; Mircea Stirbet; Larry Turlington; Lynn Vogel; Haipeng Wang; Katherine Wilson; Frank

    2007-06-25

    We describe the activities underway at JLab to develop new CW cryomodules capable of transporting up to Ampere-levels of beam currents for use in ERLs and FELs. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping and ancillary components are optimized for this application. Designs are being developed for low-frequency (750 MHz), Ampere-class compact FELs and for high-frequency (1.5 GHz), 100 mA configurations. These designs and concepts can easily be scaled to other frequencies. We present the results of conceptual design studies, simulations and prototype measurements. These modules are being developed for the next generation ERL based high power FELs but may be useful for other applications such as high energy light sources, electron cooling, electron-ion colliders, industrial processing etc.

  5. Studies of a Linac Driver for a High Repetition Rate X-Ray FEL

    SciTech Connect

    Venturini, M.; Corlett, J.; Doolittle, L.; Filippetto, D.; Papadopoulos, C.; Penn, G.; Prosnitz, D.; Qiang, J.; Reinsch, M.; Ryne, R.; Sannibale, F.; Staples, J.; Wells, R.; Wurtele, J.; Zolotorev, M.; Zholents, A.

    2011-06-01

    We report on on-going studies of a superconducting CW linac driver intended to support a high repetition rate FEL operating in the soft x-rays spectrum. We present a pointdesign for a 1.8 GeV machine tuned for 300 pC bunches and delivering low-emittance, low-energy spread beams as needed for the SASE and seeded beamlines.

  6. High-efficiency FEL-oscillator with Bragg resonator operated in reversed guide field regime

    SciTech Connect

    Kaminsky, A.K.; Sedykh, S.N.; Sergeyev, A.P.

    1995-12-31

    The aim of the present work was to develop a narrow-band FEL-oscillator working in millimeter wavelength with, high efficiency. It looked promising to combine the high selective property of Bragg resonator with high efficiency and other advantages of FEL operation in the reversed guide-field regime. An experimental study of the FEL was performed using lilac LIU-3000 (JINR, Dubna) with the electron energy of 1 MeV, beam current up to 200 A and pulse duration of 200 ns. The beam was injected into the internction region with guide magnetic field of 2.9 kGs. Transverse oscillations of electrons were pumped by the helical wiggler with the period length of 6 cm and the field slowly up-tapering over the initial 6 periods. The FEI electrodynamic system consisted of a circular waveguide with diameter 20 mm and two Bragg reflectors. The H wave of the circular waveguide was shown for operation. Two effective feedback waves were observed in {open_quotes}cold{close_quotes} electrodynamic measurement in correspondence with calculations; the E wave near the frequency of 31. 5 GHz and the E wave - 37.5 GHz. The width of the both reflection resonances was about 2%. In {open_quotes}hot{close_quotes} experiments the radiation on the designed H wave and frequencies corresponding to the both feedback waves was registered separately. Selection of the frequency was realized by varying of the wiggler field strength. The spectrum was measured with a set of the cut--off waveguide filters with inaccuracy less than 2%. Calibrated Semiconductor detectors wire used to measure the radiation power. The radiation with the frequencies of 37.5 and 31.5 GHz was observed in vicinity of the wiggler field amplitude of 2.5 kGs. The measured spectrum width of the output FEL-oscillator radiation did not exceed the width of the Bragg reflector resonances for the both feedback waves.

  7. Thermal Acoustic Sensor for High Pulse Energy X-ray FEL Beams

    SciTech Connect

    Smith, T.J.; Frisch, J.C.; Kraft, E.M.; Loos, J.; Bentsen, G.S.; /Rochester U.

    2011-12-13

    The pulse energy density of X-ray FELs will saturate or destroy conventional X-ray diagnostics, and the use of large beam attenuation will result in a beam that is dominated by harmonics. We present preliminary results at the LCLS from a pulse energy detector based on the thermal acoustic effect. In this type of detector an X-ray resistant material (boron carbide in this system) intercepts the beam. The pulse heating of the target material produces an acoustic pulse that can be detected with high frequency microphones to produce a signal that is linear in the absorbed energy. The thermal acoustic detector is designed to provide first- and second-order calorimetric measurement of X-ray FEL pulse energy. The first-order calorimetry is a direct temperature measurement of a target designed to absorb all or most of the FEL pulse power with minimal heat leak. The second-order measurement detects the vibration caused by the rapid thermoelastic expansion of the target material each time it absorbs a photon pulse. Both the temperature change and the amplitude of the acoustic signal are directly related to the photon pulse energy.

  8. Statistical properties of radiation power levels from a high-gain free-electron laser at and beyond saturation

    SciTech Connect

    Schroeder, Carl B.; Fawley, William M.; Esarey, Eric

    2002-09-24

    We investigate the statistical properties (e.g., shot-to-shot power fluctuations) of the radiation from a high-gain free-electron laser (FEL) operating in the nonlinear regime. We consider the case of an FEL amplifier reaching saturation whose shot-to-shot fluctuations in input radiation power follow a gamma distribution. We analyze the corresponding output power fluctuations at and beyond first saturation, including beam energy spread effects, and find that there are well-characterized values of undulator length for which the fluctuation level reaches a minimum.

  9. Very high gain Nd:YLF amplifiers

    SciTech Connect

    Knights, M.G.; Thomas, M.D.; Chicklis, E.P.; Rines, G.A.; Seka, W.

    1988-05-01

    The authors report on high gain Nd:YLF rod amplifiers in which single-pass, small signal gains of over 1700 have been obtained along with stored energy densitiesgreater than or equal to0.4J/cm/sup 3/. The ability of Nd:YLF amplifiers to support such gains is a result of high parasitic oscillation thresholds, due primarily to the low refractive index of the material. These results suggest that Nd:YLF is an excellent candidate for amplifiers where high specific stored energies and/or very high gains are required.

  10. High-gain lasing and polarization switch with a distributed optical-klystron free-electron laser.

    PubMed

    Wu, Y K; Vinokurov, N A; Mikhailov, S; Li, J; Popov, V

    2006-06-01

    This Letter reports the first experimental results from the world's first distributed optical-klystron (DOK) free-electron laser (FEL), the DOK-1 FEL, at Duke University. The DOK-1 FEL is a hybrid system, comprised of four wigglers: two horizontal and two helical. With the DOK-1 FEL, we have obtained the highest FEL gain among all storage ring based FELs at 47.8% (+/-2.7%) per pass. We have also demonstrated that the FEL gain can be enhanced by increasing electron bunching using wigglers with a different polarization. Furthermore, we have realized controlled polarization switches of the FEL beam by a nonoptical means through the manipulation of a buncher magnet. PMID:16803315

  11. High temperature electronic gain device

    DOEpatents

    McCormick, J. Byron; Depp, Steven W.; Hamilton, Douglas J.; Kerwin, William J.

    1979-01-01

    An integrated thermionic device suitable for use in high temperature, high radiation environments. Cathode and control electrodes are deposited on a first substrate facing an anode on a second substrate. The substrates are sealed to a refractory wall and evacuated to form an integrated triode vacuum tube.

  12. Chirped pulse amplification at VISA-FEL

    NASA Astrophysics Data System (ADS)

    Agustsson, R.; Andonian, G.; Babzien, M.; Ben-Zvi, I.; Frigola, P.; Huang, J.; Murokh, A.; Palumbo, L.; Pellegrini, C.; Reiche, S.; Rosenzweig, J.; Travish, G.; Vicario, C.; Yakimenko, V.

    2004-08-01

    Chirped beam manipulations are of the great interest to the free electron laser (FEL) community as potential means of obtaining ultra short X-ray pulses. The experiment is under way at the accelerator test facility (ATF) at Brookhaven National Laboratory (BNL) to study the FEL process limits with the under-compressed chirped electron beam. High gain near-saturation SASE operation was achieved with the strongly chirped beam (˜2.8% head-to-tail). The measured beam dynamics and SASE properties are presented, as well as the design parameters for the next round of experiment utilizing the newly installed UCLA/ATF chicane compressor.

  13. Experimental results of a sheet-beam, high power, FEL amplifier with application to magnetic fusion research

    SciTech Connect

    Cheng, S.; Destler, W.W.; Granatstein, V.L.

    1995-12-31

    The experimental study of sheet-beam FELs as candidate millimeter-wave sources for heating magnetic fusion plasmas has achieved a major milestone. In a proof-of-principle, pulsed experiment, saturated FEL amplifier operation was achieved with 250 kW of output power at 86 GHz. Input microwave power was 1 kW, beam voltage was 450 kV and beam current was 17 A. The planar wiggler had a peak value of 3.8 kG, a period of 0.96 cm and was 71 cm long. The linear gain of 30 dB, saturated gain of 24 dB and saturated efficiency of 3% all are in good agreement with theoretical prediction. Follow-on work would include development of a thermionic sheet-beam electron-gun compatible with CW FEL operation, adding a section of tapered wiggler to increase the output power to levels in excess of 1 megawatt, and increasing the FEL frequency.

  14. AN EXPERIMENTAL TEST OF SUPERRADIANCE IN A SINGLE PASS SEEDED FEL.

    SciTech Connect

    WATANABE, T.; LIU, D.; MURPHY, J.B.; ROSE, J.; SHAFTAN, T.; TSANG, T.; WANG, X.J.; YU, L.H.

    2005-08-21

    Superradiance and nonlinear evolution of a FEL pulse in a single-pass FEL were experimentally demonstrated at the National Synchrotron Light Source (NSLS) Source Development Laboratory (SDL). The experiment was performed using a 1.5 ps high-brightness electron beam and a 100fs Ti:Sapphire seed laser. The seed laser and electron beam interact in the 10 meter long NISUS undulator with a period of 3.89 cm. The FEL spectrum, energy and pulse length along the undulator were measured. FEL saturation was observed, and gain of more the 200 (relative to seed laser) was measured. Both FEL spectrum widening and pulse length shortening were observed; FEL pulses as short as 65 fs FWHM were measured. The superradiance and nonlinear evolution were also simulated using the numerical code GENESIS1.3 yielding good agreement with the experimental results.

  15. The ETA-II induction linac as a high-average-power FEL driver

    NASA Astrophysics Data System (ADS)

    Nexsen, W. E.; Atkinson, D. P.; Barrett, D. M.; Chen, Y.-J.; Clark, J. C.; Griffith, L. V.; Kirbie, H. C.; Newton, M. A.; Paul, A. C.; Sampayan, S.; Throop, A. L.; Turner, W. C.

    1990-10-01

    The Experimental Test Accelerator II (ETA-II) is the first induction linac designed specifically to FEL requirements. It is primarily intended to demonstrate induction accelerator technology for high-average-power, high-brightness electron beams, and will be used to drive a 140 and 250 GHz microwave FEL for plasma heating experiments in the Microwave Tokamak Experiment (MTX) at LLNL. Its features include high-vacuum design which allows the use of an intrinsically bright dispenser cathode, induction cells designed to minimize BBU growth rate, and careful attention to magnetic alignment to minimize radial sweep due to beam corkscrew. The use of magnetic switches allows high-average-power operation. At present ETA-II is being used to drive 140 GHz plasma heating experiments. These experiments require nominal beam parameters of 6 MeV energy, 2 kA current, 20 ns pulse width and a brightness of 1 × 108 A/(m rad)2 at the wiggler with a pulse repetition frequency (prf) of 0.5 Hz. Future 250 GHz experiments require beam parameters of 10 MeV energy, 3 kA current, 50 ns pulse width and a brightness of 1 × 108 A/(m rad)2 with a 5 kHz prf for 0.5 s. In this paper we discuss the present status of ETA-II parameters and the phased development program necessary to satisfy these future requirements.

  16. Study of waveguide resonators for FEL operating at submillimeter wavelengths

    SciTech Connect

    Yakover, I.M.; Pinhasi, Y.; Gover, A.

    1995-12-31

    This paper presents theoretical results of waveguide resonator study for FEL operating at the submillimeter wavelength region. Because of increased ohmic losses it is harder to obtain high Q waveguide cavities at these wavelengths. The following unconventional multimode waveguides: metal-dielectric, corrugated and curved parallel plates, were considered. The type and structure of the operating modes were determined and their attenuation constant, effective mode area and wave impedance were calculated. On the basis of this analysis small-signal gain simulations were made. We have performed a parametric study of the various FEL oscillator cavity designs based on the parameters of the Israeli Tandem FEL experiment. It was found that an FEL utilizing unconventional waveguides has much better performance in comparison to an FEL based on conventional multimode rectangular and circular waveguides. In particular, promising design parameters for a sub-mm wavelength FEL utilizing a metal-dielectric waveguide were identified: gain of 45%/Amp and ohmic losses of 2% at frequency 300 GHz, and gain of 20%/Amp and ohmic losses 1% at frequency 675 GHz.

  17. Optics-free x-ray FEL oscillator

    SciTech Connect

    Litvinenko, V.N.; Hao, Y.; Kayran, D.; Trbojevic, D.

    2011-03-28

    There is a need for an Optics-Free FEL Oscillators (OFFELO) to further the advantages of free-electron lasers and turning them in fully coherent light sources. While SASE (Self-Amplified Spontaneous Emission) FELs demonstrated the capability of providing very high gain and short pulses of radiation and scalability to the X-ray range, the spectra of SASE FELs remains rather wide ({approx}0.5%-1%) compared with typical short wavelengths FEL-oscillators (0.01%-0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes with very high average and peak spectral brightness either very complex or, strictly speaking, impossible. In this paper, we discuss lattice of the X-ray optics-free FEL oscillator and present results of initial computer simulations of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. We also discuss main limiting factors and feasibility of X-ray OFFELO.

  18. Sensitivity and alternative operating point studies on a high charge CW FEL injector test stand at CEBAF

    SciTech Connect

    Liu, H.; Kehne, D.; Benson, S.

    1995-12-31

    A high charge CW FEL injector test stand is being built at CEBAF based on a 500 kV DC laser gun, a 1500 MHz room-temperature buncher, and a high-gradient ({approx}10 MV/m) CEBAF cryounit containing two 1500 MHz CEBAF SRF cavities. Space-charge-dominated beam dynamics simulations show that this injector should be an excellent high-brightness electron beam source for CW UV FELs if the nominal parameters assigned to each component of the system are experimentally achieved. Extensive sensitivity and alternative operating point studies have been conducted numerically to establish tolerances on the parameters of various injector system components. The consequences of degraded injector performance, due to failure to establish and/or maintain the nominal system design parameters, on the performance of the main accelerator and the FEL itself are discussed.

  19. The Galileo high gain antenna deployment anomaly

    NASA Technical Reports Server (NTRS)

    Johnson, Michael R.

    1994-01-01

    On April 11, 1991, the Galileo spacecraft executed a sequence that would open the spacecraft's High Gain Antenna. The Antenna's launch restraint had been released just after deployment sequence, the antenna, which opens like an umbrella, never reached the fully deployed position. The analyses and tests that followed allowed a conclusive determination of the likely failure mechanisms and pointed to some strategies to use for recovery of the high gain antenna.

  20. 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

  1. Spontaneous emission effects in optically pumped x-ray FEL

    SciTech Connect

    Smetanin, I.V.; Grigor`ev, S.V.

    1995-12-31

    An effect of spontaneous emission in both quantum and classical regimes of the optically pumped X-ray free electron laser (FEL) in investigated. The quantum properties of an FEL are determined by the ratio of the separation {h_bar} between the absorption and emission lines (i.e. the quanta emitted) and their effective width {Delta}{epsilon} {eta}={h_bar}/{Delta}{epsilon}. In the conventional classical regime {eta} {much_lt} 1 an electron emits and absorbes a great number of shortwavelength photons over the interaction region, the gain in FEL being the result of these competitive processes. In the quantum limit {eta} {much_gt} 1 the emission and absorption lines are completely separated and thus the FEL becomes a two-level quantum oscillator with a completely inverted active medium. Spontaneous emission causes the electron to leave the range of energies where resonant interaction with the laser field occurs, thus effectively reducing the number of particles that take part in generating the induced X-ray signal. This effect is found to be crucial for lasing in optically pumped X-ray FEL. The characteristic relaxation times are calculated for both classical and quantum FEL regimes. It is shown that spontaneous emission results in FEL electron beam threshold current, which is of rather high value. An optimal range of pumping laser intensities is determined.

  2. High-gain harmonic generation of soft X-rays with the `fresh bunch` technique

    SciTech Connect

    Yu, Li-Hua; Ben-Zvi, I.

    1996-10-01

    We report numerical simulations (using the TDA code) and analytic verification of the generation of 64 {Angstrom} high power soft X- rays from an exponential regime single pass seeded FEL. The seed is generated in the FEL using the High Gain Harmonic Generation (HGHG) technique combined with the `Fresh bunch` technique. A seed pulse at 2944 {Angstrom} is generated by conventional laser techniques. The seed pulse produces an intense energy modulation of the rear part of a I GeV, 1245 {Angstrom} electron beam in a `modulator` wiggler. In the `radiator` wiggler, (resonant to 64 {Angstrom}), the energy modulation creates beam density modulation followed by radiation of the 46{sup th} harmonic of the seed. We use a magnetic delay to position the 64 A{Angstrom} radiation at the undisturbed front of the bunch to serve as a seed for a single pass, exponential growth FEL. After a 9 m long exponential section followed by a 7 m long tapered section the radiation power reaches 3.3 GW.

  3. Physics design for the ATA (Advanced Test Accelerator) tapered wiggler 10. 6. mu. FEL (Free-Electron Laser) amplifier experiment

    SciTech Connect

    Fawley, W.M.

    1985-05-09

    The design and construction of a high-gain, tapered wiggler 10.6 ..mu.. Free Electron Laser (FEL) amplifier to operate with the 50 MeV e-beam is underway. This report discussed the FEL simulation and the physics motivations behind the tapered wiggler design and initial experimental diagnostics.

  4. A compact FEL upconverter of coherent radiation

    SciTech Connect

    Liu, Y.; Marshall, T.C.

    1995-12-31

    The objective is to generate a powerful millimeter-wave FEL signal in a single pass, using a coherent microwave source (24GHz) to prebunch the electron beam for a harmonically-related wave (72GHz). We use the Columbia FEL facility, operating the electron beam at 600kV, 100A; undulator period = 1.85cm and 250G (K = 0.25); electron beam diameter = 3mm inside a 8.5 mm ID drift tube; guiding field of 8800G. Under these conditions, both the microwave signal (5kW input) and the millimeter signal will show travelling-wave gain in the TE11 mode. We report initial experimental results for the millimeter wave spectrum and find an overall power gain of {approximately}20 for the 24GHz input wave. Also presented will be numerical solutions of the wave growth using the FEL equations with slippage. This device has the advantage of producing a high-power FEL output in a single-pass travelling-wave configuration, obtaining a millimeter wave which is phase-referenced to a coherent laboratory source.

  5. Design of a high average-power FEL driven by an existing 20 MV electrostatic-accelerator

    SciTech Connect

    Kimel, I.; Elias, L.R.

    1995-12-31

    There are some important applications where high average-power radiation is required. Two examples are industrial machining and space power-beaming. Unfortunately, up to date no FEL has been able to show more than 10 Watts of average power. To remedy this situation we started a program geared towards the development of high average-power FELs. As a first step we are building in our CREOL laboratory, a compact FEL which will generate close to 1 kW in CW operation. As the next step we are also engaged in the design of a much higher average-power system based on a 20 MV electrostatic accelerator. This FEL will be capable of operating CW with a power output of 60 kW. The idea is to perform a high power demonstration using the existing 20 MV electrostatic accelerator at the Tandar facility in Buenos Aires. This machine has been dedicated to accelerate heavy ions for experiments and applications in nuclear and atomic physics. The necessary adaptations required to utilize the machine to accelerate electrons will be described. An important aspect of the design of the 20 MV system, is the electron beam optics through almost 30 meters of accelerating and decelerating tubes as well as the undulator. Of equal importance is a careful design of the long resonator with mirrors able to withstand high power loading with proper heat dissipation features.

  6. INTRA-UNDULATOR MEASUREMENTS AT VISA FEL.

    SciTech Connect

    MUROKH,A.; FRIGOLA,P.; ET AL; JOHNSON,E.; WANG,X.J.; YAKIMENKO,V.

    2000-08-13

    We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimizing the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed.

  7. Intra-undulator measurements at VISA FEL

    SciTech Connect

    Murokh, A; Frigola, P; Pellegrini, C; Rosenzweig, J; Tremaine, A; Johnson, E; Wang, X J; Yakimenko, V; Klaisner, L; Nuhn, H D; Toor, A

    2000-08-10

    We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimizing the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed.

  8. Photon Source Capabilities of the Jefferson Lab FEL

    SciTech Connect

    Benson, S. V.; Douglas, D. R.; Evtushenko, P.; Hannon, F. E.; Hernandez-Garcia, C.; Klopf, J. M.; Legg, R. A.; Neil, G. R.; Shinn, M. D.; Tennant, C. D.; Zhang, S.; Williams, G. P.

    2013-03-22

    Jefferson Lab operates a superconducting energy recovered linac which is operated with CW RF and which powers oscillator-based IR and UV Free Electron Lasers (FELs) with diffraction limited sub-picosecond pulses with >10{sup 13} photons per pulse (1.0%BW) at pulse repetition frequencies up to 75 MHz. Useful harmonics extend into the vacuum ultraviolet (VUV). Based on FEL model calculations validated using this facility, we have designed both an oscillator-based VUV-FEL that would produce 6 10{sup12} coherent (0.5% BW) 100 eV photons per pulse at multi-MHz repetition rates in the fundamental, and a dual FEL configuration that would allow simultaneous lasing lasing at THz and UV wavelengths. The VUV-FEL would utilize a novel high gain, low Q cavity, while the THz source would be an FEL oscillator with a short wiggler providing diffraction limited pulses with pulse energy exceeding 50 microJoules. The THz source would use the exhaust beam from a UVFEL. Such multiphoton capabilities would provide unique opportunities for out of equilibrium dynamical studies at time-scales down to 50 fs. The fully coherent nature of all these sources results in peak and average brightness values that are many orders of magnitude higher than storage rings. We acknowledge support from the Commonwealth of Virginia. Jefferson Lab is supported by the U.S. DOE under Contract No. DE-AC05-84-ER40150.

  9. Resonance hard radiation in a gas-loaded FEL

    SciTech Connect

    Gevorgian, L.A.

    1995-12-31

    The process of induced radiation under the condition when the relativistic beam oscillation frequency coincides with the plasma frequency of the FEL filling gas, is investigated. Such a resonance results in a giant enhancement of interaction between electrons and photons providing high gain in the hard FEL frequency region. Meanwhile the spectralwidth of the spontaneous radiation is broadened significantly. A method is proposed for maintaining the synchronism between the electron oscillation frequency and the medium plasma frequency, enabling to transform the electron energy into hard radiation with high efficiency.

  10. FEL on slow cyclotron wave

    SciTech Connect

    Silivra, A.

    1995-12-31

    A physical mechanism of interaction of fast electromagnetic wave with slow cyclotron wave of relativistic electron beam in a FEL with helical wiggler field is described. It is shown that: (1) interaction is possible for both group of steady state electron trajectories (2) positive gain is achieved within certain interval of guide field strength (3) operation wavelength for group 1 trajectories ({Omega}{sub 0}/{gamma} < k{omega}{upsilon}{parallel}) is shorter than for the conventional FEL synchronism. A nonlinear analysis shows that efficiency of slow cyclotron FEL is restricted mainly by a breakdown of a single electron synchronism due to dependence of (modified) electron cyclotron frequency on an energy of electron. Nevertheless, as numerical simulation shows, typical efficiency of 15 % order is achieved in millimeter wavelength band for the midrelativistic ({gamma}= 3 {divided_by} 4) slow cyclotron wave FEL. Tapering of magnetic field results in a substantial increase of efficiency.

  11. Production of high power microwaves for particle acceleration with an FEL bunched electron beam

    NASA Astrophysics Data System (ADS)

    Gardelle, J.; Lefevre, T.; Marchese, G.; Padois, M.; Rullier, J. L.; Donohue, J. T.

    1999-06-01

    Among the studies in the framework of high gradient linear electron-positron collider research, the Two-Beam Accelerator (TBA) is a very promising concept, and two projects are in progress, the Compact Linear Collider project at CERN (W. Schnell, Report no. CERN SL/92-51 and CLIC note 184; K. Hübner, CERN/PS 92-43, CLIC note 176; S. Van der Meer, CERN/PS 89-50, CLIC note 97.) and the Relativistic Klystron-TBA project at LBNL (Technical Review Committee, International Linear Collider Technical Review Committee Report 1995, SLAC-R-95-471, 1995). In a TBA an extremely intense low-energy electron beam, called the drive beam, is bunched at the desired operating frequency, and upon passing through resonant cavities generates radio-frequency power for accelerating the main beam. Among the different approaches to the production of a suitable drive beam, the use of an FEL has been proposed and is under active study at CEA/CESTA.

  12. Hybrid optical antenna with high directivity gain.

    PubMed

    Bonakdar, Alireza; Mohseni, Hooman

    2013-08-01

    Coupling of a far-field optical mode to electronic states of a quantum absorber or emitter is a crucial process in many applications, including infrared sensors, single molecule spectroscopy, and quantum metrology. In particular, achieving high quantum efficiency for a system with a deep subwavelength quantum absorber/emitter has remained desirable. In this Letter, a hybrid optical antenna based on coupling of a photonic nanojet to a metallo-dielectric antenna is proposed, which allows such efficient coupling. A quantum efficiency of about 50% is predicted for a semiconductor with volume of ~λ³/170. Despite the weak optical absorption coefficient of 2000 cm(-1) in the long infrared wavelength of ~8 μm, very strong far-field coupling has been achieved, as evidenced by an axial directivity gain of 16 dB, which is only 3 dB below of theoretical limit. Unlike the common phased array antenna, this structure does not require coherent sources to achieve a high directivity. The quantum efficiency and directivity gain are more than an order of magnitude higher than existing metallic, dielectric, or metallo-dielectric optical antenna. PMID:23903124

  13. Mechanisms of the Rosetta high gain antenna

    NASA Astrophysics Data System (ADS)

    Pereira, Carlos

    2001-09-01

    This paper describes the antenna pointing mechanism (APM) and the hold down and release mechanism (HRM) used in the high gain antenna of the ROSETTA mission. The hold down and release mechanism consists of three units which compensate the tolerance mismatch between antenna and spacecraft through incorporation of potting rings. Given that the activation mode is pyrotechnic, release shock is a major concern and is minimised through integration of shock absorbers which allow stroking of the separation nuts. The antenna pointing mechanism is a dual drive (azimuth over elevation) unit which allows controlled rotation of the antenna. The drive units incorporate spring loaded end stops to prevent the antenna from hitting the spacecraft, and optical encoders which register the absolute position of the antenna. The pointing and the hold down mechanisms of the ROSETTA antenna are fully qualified and will withstand the high launch loads of the Ariane-5 and the environmental demands of deep space operation.

  14. Beam Line Commissioning of a UV/VUV FEL at Jefferson Lab

    SciTech Connect

    Benson, Stephen; Blackburn, Keith; Bullard, Daniel; Clavero Perez, Cesar; Coleman, James; Dickover, Cody; Douglas, David; Ellingsworth, Forrest; Evtushenko, Pavel; Hernandez-Garcia, Carlos; Gould, Christopher; Gubeli, Joseph; Hardy, David; Jordan, Kevin; Klopf, John; James, Kortze; Legg, Robert; Marchlik, Matthew; Moore, Steven; Neil, George; Powers, Thomas; Sexton, Daniel; Shinn, Michelle D; Tennant, Christopher; Walker, Richard; Williams, Gwyn; Wilson, Frederick; Zhang, Shukui

    2011-08-01

    Many novel applications in photon sciences require very high brightness and/or short pulses in the vacuum ultra-violet (VUV). Jefferson Lab has commissioned a UV oscillator with high gain and has transported the third harmonic of the UV to a user lab. The experimental performance of the UV FEL is much better than simulated performance in both gain and efficiency. This success is important for efforts to push towards higher gain FELs at short wavelengths where mirrors absorb strongly. We will report on efforts to characterize the UV laser and the VUV coherent harmonics as well as designs to lase directly in the VUV wavelength range.

  15. Partial covariance mapping techniques at FELs

    NASA Astrophysics Data System (ADS)

    Frasinski, Leszek

    2014-05-01

    The development of free-electron lasers (FELs) is driven by the desire to access the structure and chemical dynamics of biomolecules with atomic resolution. Short, intense FEL pulses have the potential to record x-ray diffraction images before the molecular structure is destroyed by radiation damage. However, even during the shortest, few-femtosecond pulses currently available, there are some significant changes induced by massive ionisation and onset of Coulomb explosion. To interpret the diffraction images it is vital to gain insight into the electronic and nuclear dynamics during multiple core and valence ionisations that compete with Auger cascades. This paper focuses on a technique that is capable to probe these processes. The covariance mapping technique is well suited to the high intensity and low repetition rate of FEL pulses. While the multitude of charges ejected at each pulse overwhelm conventional coincidence methods, an improved technique of partial covariance mapping can cope with hundreds of photoelectrons or photoions detected at each FEL shot. The technique, however, often reveals spurious, uninteresting correlations that spoil the maps. This work will discuss the strengths and limitations of various forms of covariance mapping techniques. Quantitative information extracted from the maps will be linked to theoretical modelling of ionisation and fragmentation paths. Special attention will be given to critical experimental parameters, such as counting rate, FEL intensity fluctuations, vacuum impurities or detector efficiency and nonlinearities. Methods of assessing and optimising signal-to-noise ratio will be described. Emphasis will be put on possible future developments such as multidimensional covariance mapping, compensation for various experimental instabilities and improvements in the detector response. This work has been supported the EPSRC, UK (grants EP/F021232/1 and EP/I032517/1).

  16. Design study of a longer wavelength FEL for FELIX

    SciTech Connect

    Lin, L.; Oepts, D.; Meer, A.F.G. van der

    1995-12-31

    We present a design study of FEL3, which will extend the FELIX spectral range towards a few hundred microns. A rectangular waveguide will be used to reduce diffraction losses. Calculations show that with a waveguide gap of 1 cm, only one sinusoidal mode along the guided direction can exist within the FEL gain bandwidth, thus excluding group velocity dispersion and lengthening of short radiation pulses. To incorporate FEL3 in the existing FELIX facility, two options are being considered: to combine FEL3 with FEL1 by insertion of a waveguide into FEL1, and to build a dedicated third beam line for FEL3 after the two linacs. Expected FEL performance: gain, spectrum, power, pulse shape, etc., will be presented based on numerical simulations.

  17. Scaling formulae for FEL operating in linear and non linear regime

    SciTech Connect

    Dattoli, G.; Mezi, L.; Segreto, A.

    1995-12-31

    Scaling relations for the FEL gain, including the e-beam quality effects, have been usefully exploited to design FEL devices. We propose further extension of the above formulae including high gain, inhomogeneous broadening and saturation effects. A crucial role to get these relations is the use of approximant methods generalizing the Pade procedure. We derive gain equations containing the corrections due to energy spread, emittances and field intensity. It is shown that these equations can be exploited to {open_quotes}simulate{close_quotes} the FEL evolution with an almost negligible computational effort. Comments on the role of the saturation intensity and its dependence on the e-beam quality, high gain corrections etc. are also presented.

  18. Compact FEL`s based on slow wave wigglers

    SciTech Connect

    Riyopoulos, S.

    1995-12-31

    Slow waves excited in magnetron-type cavities are attractive canditates as wigglers for compact Free Electron Lasers. Because of group velocities much below the speed of light, slow waves offer an order of magnitude increase in FEL gain under given circulating power in the wiggler resonator, compared to fast wave wigglers of similar period. In addition, they offer the versatility of operation either at modest beam energy via upshifing of the fundamental wavelength, or at low beam energy benefiting from the submillimeter wiggler harmonics. Because the main electron undulation is in the transverse direction for all spatial harmonics, the radiated power is increased by a factor {gamma}{sup 2} relative to the Smith-Purcell approach that relies on axial electron undulation. Technical advantages offered by magnetron-type wiggles are: the generation of the wiggler microwaves and the FEL interaction take place inside the same cavity, avoiding the issue of high power coupling between cavities; the excitation of wiggler microwaves relies on distributed electron emission from the cavity wall and does not require separate beam injection.

  19. Sideband elimination and high efficiencies in a strongly tapered FEL amplifier

    SciTech Connect

    Bhattacharjee, A.; Chen, J.

    1995-12-31

    Recently, an analytical theory has shown that sideband instabilities can be eliminated in a strongly tapered FEL amplifier, leading to high efficiencies. It is found that a drastic suppression of the sideband spectrum occurs due to a continuous detuning effect which causes the real frequency of the most unstable sideband mode to vary continuously along the wiggler axis in the presence of a strong taper, with the consequence that no sideband can grow significantly before it is tuned away. Assuming extremely strongly pre-bunched beams with zero thermal spread, ideal efficiencies exceeding 60% were predicted by the theory with sideband intensities suppressed by nearly eight orders of magnitude with respect to the intensity of the primary signal. The theoretical predictions have been tested and verified by a one-dimensional numerical simulation. The numerical simulations permit us to go beyond the scope of the analytical model and allow us to examine (i) if optimization of strongly tapered wiggler configurations can allow us to achieve the desired high efficiencies within acceptable length constraints, and (ii) whether the high ideal efficiencies predicted by theory survive in the presence of partial pre-bunching and finite thermal spread of electron beams. By experimenting with different tapering schemes, we have found interesting strongly tapered configurations in which the accessible electron phase-space area remains nearly constant, with realistic assumptions on pre-bunching and thermal spread of the electron beam. In particular, for parameters representative of the Livermore experiments we obtain efficiencies in the rage 40-50% with thermal spreads in the range 0.5-1 % and pre-bunched electron phases in the range 2 {pi}/ 3 using a wiggler 5 meters long. The optical quality of the radiation produced is free of parasitic sideband instabilities which do not grow beyond noise levels.

  20. An FEL design code running on Mathcad(trademark)

    NASA Astrophysics Data System (ADS)

    Nguyen, D. C.; Gierman, S. M.; Oshea, P. G.

    We present a simple computer code called FEL-CAD that runs on the Mathcad(trademark) software. FEL-CAD gives estimates of the expected performance of a low-gain Compton FEL oscillator driven by an rf linac. The code provides fast, albeit approximate, answers to basic FEL design questions. Scaling can be done by varying the wiggler, the linac, the electron beam and the optical resonator parameters.

  1. Echo-Enabled Harmonic Generation for Seeded FELs

    SciTech Connect

    Stupakov, G.; /SLAC

    2011-05-19

    In the x-ray wavelengths, the two leading FEL concepts are the self-amplified spontaneous emission (SASE) configuration and the high-gain harmonic generation (HGHG) scheme. While the radiation from a SASE FEL is coherent transversely, it typically has rather limited temporal coherence. Alternatively, the HGHG scheme allows generation of fully coherent radiation by up-converting the frequency of a high-power seed laser. However, due to the relatively low up-frequency conversion efficiency, multiple stages of HGHG FEL are needed in order to generate x-rays from a UV laser. The up-frequency conversion efficiency can be greatly improved with the recently proposed echo-enabled harmonic generation (EEHG) technique. In this work we will present the concept of EEHG, and address some practically important issues that affect the performance of the seeding. We show how the EEHG can be incorporated in the FEL scheme and what is the expected performance of the EEHG seeded FEL. We will then briefly describe the first proof-of-principle EEHG experiment carried out at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We will also discuss latest advances in the echo-scheme approach, and refer to subsequent modifications of the original concept.

  2. Progress toward high-gain laser fusion

    SciTech Connect

    Storm, E.

    1988-09-28

    A 1985-1986 Review of the US inertial confinement fusion program by the National Academy of Sciences concluded that five more years might be required to obtain enough data to determine the future course of the program. Since then, data from the Nova laser and from the Halite/Centurion program have resolved most of the outstanding problems identified by the NAS review. In particular, we now believe that we can produce a sufficiently uniform target; that we can keep the energy content in hot electrons and high-energy photons low enough (/approximately/1--10% of drive energy, depending on target design) and achieve enough pulse-shaping accuracy (/approximately/10%, with a dynamic range of 100:1) to keep the fuel on a near-Fermi-degenerate adiabat; that we can produce an /approximately/100-Mbar pressure pulse of sufficient uniformity (/approximately/1%), and can we control hydrodynamic instabilities so that the mix of the pusher into the hot spot is low enough to permit marginal ignition. These results are sufficiently encouraging that the US Department of Energy is planning to complete a 10-MJ laboratory microfusion facility to demonstrate high-gain ICF in the laboratory within a decade. 22 refs., 1 fig.

  3. Progress toward high-gain laser fusion

    NASA Astrophysics Data System (ADS)

    Storm, Erik

    1988-09-01

    A 1985 to 1986 Review of the U.S. inertial confinement fusion program by the National Academy of Sciences concluded that five more years might be required to obtain enough data to determine the future course of the program. Since then, data from the Nova laser and from the Halite/Centurion program have resolved most of the outstanding problems identified by the NAS review. In particular, we now believe that we can produce a sufficiently uniform target; that we can keep the energy content in hot electrons and high-energy photons low enough (approximately 1 to 10 percent of drive energy, depending on target design) and achieve enough pulse-shaping accuracy (approximately 10 percent, with a dynamic range of 100:1) to keep the fuel on a near-Fermi-degenerate adiabat; that we can produce an approximately 100-Mbar pressure pulse of sufficient uniformity (approximately 1 percent), and can control hydrodynamic instabilities so that the mix of the pusher into the hot spot is low enough to permit marginal ignition. These results are sufficiently encouraging that DOE is planning to complete a 10-MJ laboratory microfusion facility to demonstrate high-gain ICF in the laboratory within a decade.

  4. The VISA FEL undulator

    SciTech Connect

    Carr, R.; Cornacchia, M.; Emma, P.

    1998-08-01

    The Visible-Infrared SASE Amplifier (VISA) FEL is an experimental device designed to show Self Amplified Spontaneous Emission (SASE) to saturation in the visible light energy range. It will generate a resonant wavelength output from 800--600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is the first SASE FEL designed to reach saturation, and its diagnostics will provide important checks of theory. This paper includes a description of the VISA undulator, the magnet measuring and shimming system, and the alignment strategy. VISA will have a 4 m pure permanent magnet undulator comprising four 99 cm segments, each with 55 periods of 18 mm length. The undulator has distributed focusing built into it, to reduce the average beta function of the 70--85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walkoff, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, the authors expect to be able to control trajectory walkoff to less than {+-}50 {micro}m per field gain length.

  5. THE VISA FEL UNDULATOR

    SciTech Connect

    CARR,R.; CORNACCHIA,M.; EMMA,P.; NUHN,H.D.; FULAND,R.; JOHNSON,E.; RAKOWSKY,G.; LIDIA,S.; BERTOLINI,L.; LIBKIND,M.; FRIGOLA,P.; PELLEGRINI,C.; ROSENZWEIG,J.

    1998-08-16

    The Visible-Infrared SASE Amplifier (VISA) FEL is an experimental device designed to show Self Amplified Spontaneous Emission (SASE) to saturation in the visible light energy range. It will generate a resonant wavelength output from 800--600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is the first SASE FEL designed to reach saturation, and its diagnostics will provide important checks of theory. This paper includes a description of the VISA undulator, the magnet measuring and shimming system, and the alignment strategy. VISA will have a 4 m pure permanent magnet undulator comprising four 99 cm segments, each with 55 periods of 18 mm length. The undulator has distributed focusing built into it, to reduce the average beta function of the 70--85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walkoff or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, the authors expect to be able to control trajectory walkoff to less than {+-}50 pm per field gain length.

  6. High gain holmium-doped fibre amplifiers.

    PubMed

    Simakov, Nikita; Li, Zhihong; Jung, Yongmin; Daniel, Jae M O; Barua, Pranabesh; Shardlow, Peter C; Liang, Sijing; Sahu, Jayanta K; Hemming, Alexander; Clarkson, W Andrew; Alam, Shaif-Ul; Richardson, David J

    2016-06-27

    We investigate the operation of holmium-doped fibre amplifiers (HDFAs) in the 2.1 µm spectral region. For the first time we demonstrate a diode-pumped HDFA. This amplifier provides a peak gain of 25 dB at 2040 nm with a 15 dB gain window spanning the wavelength range 2030 - 2100 nm with an external noise figure (NF) of 4-6 dB. We also compare the operation of HDFAs when pumped at 1950 nm and 2008 nm. The 1950 nm pumped HDFA provides 41 dB peak gain at 2060 nm with 15 dB of gain spanning the wavelength range 2050 - 2120 nm and an external NF of 7-10 dB. By pumping at the longer wavelength of 2008 nm the gain bandwidth of the amplifier is shifted to longer wavelengths and using this architecture a HDFA was demonstrated with a peak gain of 39 dB at 2090 nm and 15 dB of gain spanning the wavelength range 2050 - 2150 nm. The external NF over this wavelength range was 8-14 dB. PMID:27410557

  7. A high-brightness SRF photoelectron injector for FEL light sources

    NASA Astrophysics Data System (ADS)

    Arnold, A.; Büttig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W. D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Möller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

    2008-08-01

    Most of the proposed electron accelerator projects for future FELs, ERLs or 4th generation light sources require electron beams with an unprecedented combination of high brightness, low emittance, and high average current. In all projects photoguns will be applied: DC-photoguns, normal conducting RF-photoguns (NC-guns), and superconducting RF photoguns (SRF-guns). While the concepts of DC- and NC-guns are well proofed, the SRF-gun development still possesses a high risk. Challenges are the design of the superconducting cavity, the choice of the photocathode type, its life time, a possible cavity contamination, the difficulty of coupling high average power into the gun, and, finally, the risk of beam excitation of higher-order cavity modes. In combination with SRF linacs, the SRF-guns seem to be the best solution for high average currents. Several R&D projects of SRF-gun have been launched. In this paper, we will give an overview of the progress of the SRF photoinjector development. In detail, the technical concept, the performance and the status of the Dresden Rossendorf SRF-gun project, a collaboration of BESSY, DESY, MBI and FZD, will be presented. The main design parameters of this SRF-gun are the final electron energy of 9.5 MeV, 1 mA average current, and transverse normalized emittances (rms) of 1 mm mrad at 77 pC and 2.5 mm mrad at 1 nC bunch charge. The 1.3 GHz cavity consists of three TESLA-shaped cells, a specially designed half-cell where the photocathode is placed and a choke filter in order to prevent RF losses at the cathode side. The normal-conducting photocathode with a Cs 2Te photoemission layer is cooled by liquid nitrogen. The SRF-gun cryostat consists of a stainless steel vacuum vessel, a warm magnetic shield, a liquid nitrogen-cooled thermal shield and a titanium He tank with a two-phase supply tube. The 10 kW fundamental power coupler is adopted from the ELBE cryomodule. In a first commissioning and test period the gun will be operated in

  8. High-Gain High-Field Fusion Plasma

    NASA Astrophysics Data System (ADS)

    Li, Ge

    2015-10-01

    A Faraday wheel (FW)—an electric generator of constant electrical polarity that produces huge currents—could be implemented in an existing tokamak to study high-gain high-field (HGHF) fusion plasma, such as the Experimental Advanced Superconducting Tokamak (EAST). HGHF plasma can be realized in EAST by updating its pulsed-power system to compress plasma in two steps by induction fields; high gains of the Lawson trinity parameter and fusion power are both predicted by formulating the HGHF plasma. Both gain rates are faster than the decrease rate of the plasma volume. The formulation is checked by earlier ATC tests. Good agreement between theory and tests indicates that scaling to over 10 T at EAST may be possible by two-step compressions with a compression ratio of the minor radius of up to 3. These results point to a quick new path of fusion plasma study, i.e., simulating the Sun by EAST.

  9. High-Gain High-Field Fusion Plasma.

    PubMed

    Li, Ge

    2015-01-01

    A Faraday wheel (FW)-an electric generator of constant electrical polarity that produces huge currents-could be implemented in an existing tokamak to study high-gain high-field (HGHF) fusion plasma, such as the Experimental Advanced Superconducting Tokamak (EAST). HGHF plasma can be realized in EAST by updating its pulsed-power system to compress plasma in two steps by induction fields; high gains of the Lawson trinity parameter and fusion power are both predicted by formulating the HGHF plasma. Both gain rates are faster than the decrease rate of the plasma volume. The formulation is checked by earlier ATC tests. Good agreement between theory and tests indicates that scaling to over 10 T at EAST may be possible by two-step compressions with a compression ratio of the minor radius of up to 3. These results point to a quick new path of fusion plasma study, i.e., simulating the Sun by EAST. PMID:26507314

  10. A high average current DC GaAs photocathode gun for ERLs and FELs

    SciTech Connect

    C. Hernandez-Garcia; T. Siggins; S. Benson; D. Bullard; H. F. Dylla; K. Jordan; C. Murray; G. R. Neil; Michelle D. Shinn; R. Walker

    2005-05-01

    The Jefferson Lab (JLab) 10 kW IR Upgrade FEL DC GaAs photocathode gun is presently the highest average current electron source operational in the U.S., delivering a record 9.1 mA CW, 350 kV electron beam with 122 pC/bunch at 75 MHz rep rate. Pulsed operation has also been demonstrated with 8 mA per pulse (110 pC/bunch) in 16 ms-long pulses at 2 Hz rep rate. Routinely the gun delivers 5 mA CW and pulse current at 135 pC/bunch for FEL operations. The Upgrade DC photocathode gun is a direct evolution of the DC photocathode gun used in the previous JLab 1 kW IR Demo FEL. Improvements in the vacuum conditions, incorporation of two UHV motion mechanisms (a retractable cathode and a photocathode shield door) and a new way to add cesium to the GaAs photocathode surface have extended its lifetime to over 450 Coulombs delivered between re-cesiations (quantum efficiency replenishment). With each photocathode activation quantum efficiencies above 6% are routinely achieved. The photocathode activation and performance will be described in detail.

  11. Short wavelength FELs using the SLAC linac

    SciTech Connect

    Winick, H.; Bane, K.; Boyce, R.

    1993-08-01

    Recent technological developments have opened the possibility to construct a device which we call a Linac Coherent Light Source (LCLS); a fourth generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much aborter wavelength than the 240 mn that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3-100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by Self-Amplified-Spontaneous-Emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops.

  12. Nonlinear harmonic generation in the STARS FEL

    NASA Astrophysics Data System (ADS)

    Abo-Bakr, M.; Goldammer, K.; Kamps, T.; Knobloch, J.; Kuske, B.; Leitner, T.; Meseck, A.

    2008-08-01

    BESSY proposes to build STARS, an FEL to demonstrate cascaded High Gain Harmonic Generation (HGHG). In two HGHG stages, a laser source of 700-900 nm is converted down to a wavelength of 40-70 nm. The STARS facility consists of a normal-conducting RF photoinjector, three superconducting TESLA-type acceleration modules, a magnetic bunch compressor and two stages of HGHG, each consisting of a modulator, dispersive chicane and a radiator. At the entrance of the undulator section, the beam energy is 325 MeV and the peak current is about 500 A. With these parameters, the STARS FEL reaches saturation with a peak power of 100-350 MW. A superradiant mode is also foreseen which boosts the radiation power to the GW-level. Due to nonlinear harmonic generation (NHG), free electron lasers also radiate coherently at higher harmonics of the FEL resonant frequency. STARS can hence extend its output range to even shorter wavelengths. This paper presents studies of the STARS harmonic content in the wavelength range of 6-20 nm. Seeding with high harmonic generation pulses at 32 nm is also discussed.

  13. High gain Raman amplifier with inherent gain flattening and dispersion compensation

    NASA Astrophysics Data System (ADS)

    Kakkar, Charu; Thyagarajan, K.

    2005-06-01

    We report here an inherently gain-flattened, high-gain discrete Raman fiber amplifier design with 21 dB net gain (±1.4 dB gain ripple) over 25 nm bandwidth. The amplifier design is based on a W-shape highly nonlinear fiber, in which, optimized spectral variation of leakage loss has been used to achieve inherent gain flattening of Raman gain. The proposed fiber has an additional advantage of having a high negative dispersion coefficient (∼-84 ps/km nm) over the operating range of wavelength and thus the designed discrete amplifier module, based on this fiber, is also capable of compensating dispersion accumulated in one span (70 km) of transmission through G.652 fiber. Hence, the designed module is proposed as a composite amplifier and dispersion-compensating unit for 25 nm bandwidth, which is capable of handling both attenuation and dispersion of one span of G. 652 transmission.

  14. Self-seeded injection-locked FEL amplifer

    DOEpatents

    Sheffield, Richard L.

    1999-01-01

    A self-seeded free electron laser (FEL) provides a high gain and extraction efficiency for the emitted light. An accelerator outputs a beam of electron pulses to a permanent magnet wiggler having an input end for receiving the electron pulses and an output end for outputting light and the electron pulses. An optical feedback loop collects low power light in a small signal gain regime at the output end of said wiggler and returns the low power light to the input end of the wiggler while outputting high power light in a high signal gain regime.

  15. Free Electron Lasers - Proceedings of the Beijing Fel Seminar

    NASA Astrophysics Data System (ADS)

    Chen, Jiaer; Xie, Jialin; Du, Xiangwan; Zhao, Kui

    1989-03-01

    The Table of Contents for the full book PDF is as follows: * Preface to the Series * Preface * Seminar Opening Speech * Seminar Closing Address * SECTION 1. RF LINAC BASED FEL * Richard H. Pantell * Free-Electron Lasers * Gas-Loading the FEL * High-Efficiency, High-Power Free-Electron Lasers * A Tunable Submillimeter-to-Far-Infrared Coherent Radiation Source * Kwok-Chi Dominic Chan * Recent Results from the Los Alamos Free Electron Laser * Short-Range Wakefield Effects in RF-Based Free-Electron Laser * Long-Range Wakefield Effects in RF-Based Free-Electron Laser * High-Brightness Injectors For RF-Driven Free-Electron Lasers * Computer Codes for Wakefield Analysis in RF-Based Free-Electron Laser * George R. Neil * The TRW RF Accelerator FEL Program * Superconducting Linac FEL Technology * Design Considerations of RF Oscillators * Chun-Ching Shih * Development of Multicomponent Wiggler Free Electron Lasers * Free Electron Laser Resonator * SECTION 2. INDUCTION LINAC BASED FEL * Richard J. Briggs * Overview of FEL Development with Induction Linacs at LLNL * Overview of Linear Induction Accelerators * High Current Electron-Beam Transport in Induction Linacs * Thaddeus J. Orzechowski * An Introduction to the Physics of High-Gain Free-Electron Lasers * Harmonics and Optical Guiding in Free Electron Lasers * The Electron Laser Facility: A millimeter Wave Free-Electron Laser Amplifier * The Electron Laser Facility: Measurement of Modes, Harmonics, Parametric Dependence, and Phase Shift * Paladin: A 10.6 μm Free-Electron Laser Amplifier * Aspects of Linear Induction Accelerator Technology * List of Participants

  16. X-band prebunched FEL amplifier

    SciTech Connect

    Saito, Kazuyoshi; Takayama, Ken; Ozaki, Toshiyuki

    1995-12-31

    Following the successful results of the ion-channel-guiding FEL experiments, we began a new experiment {open_quotes}prebunched FEL{close_quotes}. It is an FEL driven by prebunched beams, whose configuration is a normal FEL system with a prebuncher like the bunching section of a klystron. There are two purposes in this prebunched FEL system; (1) Demonstration of a compact/efficient FEL. Attaining the saturation power level with a short wiggler length (compact wiggler) and enhancing the power through the remaining wiggler length by wiggler tapering (high efficiency FEL). (2) Experimental simulation of multi-stage FELs in the FEL-TBA. Examination of FEL interactions with prebunched injection beams, especially, about the controllability of the output RF phase by changing the RF phase of the input seed power to the wiggler. Recent experimental results show: (1) The saturation power of 120MW has been attained at the wiggler length of 1.1m by 1.5MeV prebunched beams with a 45%-modulated 750A current. However, enhanced power has not been observed yet by wiggler tapering. (2) The current modulation of the injection beam (1.5MeV-500A) becoming higher than 30%, the adjustable range of the output RF phase was limitted less than 40 degrees by the input power of 60kW only. Detail explanations of design concept, theoretical and experimental results will be presented at the conference.

  17. Experimental and analytical study of a high gain self amplified spontaneous emission free electron laser operating in a large spectral bandwidth regime

    NASA Astrophysics Data System (ADS)

    Andonian, Gerard Cosmos

    The drive to create and measure ultra-short pulses in the x-ray regime advances the ongoing development of free electron lasers (FEL). Several proposed schemes, to shorten the pulse length of the radiation, involve driving the FEL with a chirped (linear longitudinal phase space correlation) electron beam in the self amplified spontaneous emission (SASE) mode. This dissertation examines the experiments conducted under such conditions, canvassing analytical and numerical studies of beam dynamics and radiation properties, experimental observations, and descriptions of the development of novel diagnostics. The VISA (Visible-Infrared SASE Amplifier) program has achieved saturation at 840 nm within a 4 m long undulator. A novel bunch compression mechanism during transport was discovered and ultimately responsible for the high peak current required to drive the FEL. Start-to-end simulations, detailing the dynamics from electron beam inception at the photocathode to the FEL radiation properties at the undulator, were successfully benchmarked to observable data. The VISA II experiment is an extension of this SASE FEL operating under different experimental conditions. Driving the SASE FEL with a chirped electron beam requires maintaining the chirp throughout transport by the use of sextupole magnets to correct for second-order compression effects. The emitted radiation is frequency chirped, diagnosed via a modified frequency resolved optical gating (FROG) technique. Specific numerical simulations and diagnostic developments are presented. A set of measurements, without sextupole corrections, displays anomalous features, namely large spectral bandwidth of the radiation at stable and sustained high gain lasing. The bandwidth has an rms value of 21 nm (12% full width), previously unobserved in a FEL. In addition, the far-field angular distribution yields a hollow mode structure, similar to earlier results yet more pronounced in angle. Start-to-end simulations reproduced the

  18. High gain feedback and telerobotic tracking

    NASA Technical Reports Server (NTRS)

    Koditschek, D. E.

    1987-01-01

    Asymptotically stable linear time invariant systems are capable of tracking arbitrary reference signals with a bounded error proportional to the magnitude of the reference signal (and its derivatives). It is shown that a similar property holds for a general class of nonlinear dynamical systems which includes all robots. As in the linear case, the error bound may be made arbitrarily small by increasing the magnitude of the feedback gains which stabilize the system.

  19. Some novel features of an FEL oscillator with tapered undulator

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    1995-12-31

    A one-dimensional analysis of an FEL oscillator with a linear undulator tapering is presented. Some principally novel results have been obtained. The origin of these results is in principal difference between the FEL oscillator and an FEL amplifier. In the case of the FEL amplifier the frequency of the amplified wave and all the other parameters are defined by an experimenter. Contrary to this, the case of the FEL oscillator with tapered undulator is more complicated. The lasing frequency is defined by the maximum of the small-signal gain and depends on the tapering depth in some complex way.

  20. Prospects for the FEL (Free Electron Laser)

    SciTech Connect

    Sessler, A.M.

    1989-04-01

    The future for FELs depends upon the very large number of applications which is envisioned for them. These grow out of the FEL extensive range of wavelengths, tunability, and high power capability. High power requires demonstration of optical guiding. Tunability has already been demonstrated. And the effort to extend the range of wavelengths is ever ongoing. The future will also bring more work on gas-loaded FELs, on electromagnetic wigglers, and on harmonic generation. We can, also, look forward to observation of various new effects, a few of which will be described. Finally, a list of various FEL projects around the world will be given. 12 refs., 5 figs., 8 tabs.

  1. Design considerations and analysis of potential applications of a high power ultraviolet FEL at the TESLA test facility at DESY

    NASA Astrophysics Data System (ADS)

    Pagani, C.; Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

    1999-02-01

    A possibility of constructing a high power ultraviolet free electron laser at the TESLA test facility at DESY is discussed. The proposed facility consists of a tunable master oscillator (P av˜10 mW, P peak˜10 kW, λ≃200-350 nm) and an FEL amplifier with a tapered undulator. The average and peak radiation power at the exit of the FEL amplifier is about 7 kW and 220 GW, respectively. Installation of such a facility can significantly extend scientific potential of the TESLA test facility. The UV free electron laser can be used to construct a polarized, monochromatic gamma-source with the ultimate yield up to 10 12 gamma-quanta per second and the maximal energy of about 100 MeV. An intensive gamma-source can also form the base for constructing the test facility for the TESLA positron generation system. Another accelerator application of the proposed facility is verification of the main technical solutions for the laser and the optical system to be used in the gamma-gamma option of the TESLA collider. A high average power UV laser is also promising for industrial applications.

  2. Tests of photocathodes for high repetition rate x-ray FELs at the APEX facility at LBNL

    NASA Astrophysics Data System (ADS)

    Sannibale, Fernando; Filippetto, Daniele; Qian, Houjun; Papadopoulos, Christos F.; Wells, Russell; Kramasz, Toby; Padmore, Howard; Feng, Jun; Nasiatka, James; Huang, Ruixuan; Zolotorev, Max; Staples, John W.

    2015-05-01

    After the formidable results of X-ray 4th generation light sources based on free electron lasers around the world, a new revolutionary step is undergoing to extend the FEL performance from the present few hundred Hz to MHz-class repetition rates. In such facilities, temporally equi-spaced pulses will allow for a wide range of previously non-accessible experiments. The Advanced Photo-injector EXperiment (APEX) at the Lawrence Berkeley National Laboratory (LBNL), is devoted to test the capability of a novel scheme electron source, the VHF-Gun, to generate the required electron beam brightness at MHz repetition rates. In linac-based FELs, the ultimate performance in terms of brightness is defined at the injector, and in particular, cathodes play a major role in the game. Part of the APEX program consists in testing high quantum efficiency photocathodes capable to operate at the conditions required by such challenging machines. Results and status of these tests at LBNL are presented.

  3. The Physics and Applications of High Brightness Beams: Working Group C Summary on Applications to FELS

    SciTech Connect

    Nuhn, Heinz-Dieter

    2003-03-19

    This is the summary of the activities in working group C, ''Application to FELs,'' which was based in the Bithia room at the Joint ICFA Advanced Accelerator and Beam Dynamics Workshop on July 1-6, 2002 in Chia Laguna, Sardinia, Italy. Working group C was small in relation to the other working groups at that workshop. Attendees include Enrica Chiadroni, University of Rome ape with an identical pulse length. ''La Sapienza'', Luca Giannessi, ENEA, Steve Lidia, LBNL, Vladimir Litvinenko, Duke University, Patrick Muggli, UCLA, Alex Murokh, UCLA, Heinz-Dieter Nuhn, SLAC, Sven Reiche, UCLA, Jamie Rosenzweig, UCLA, Claudio Pellegrini, UCLA, Susan Smith, Daresbury Laboratory, Matthew Thompson, UCLA, Alexander Varfolomeev, Russian Research Center, plus a small number of occasional visitors. The working group addressed a total of nine topics. Each topic was introduced by a presentation, which initiated a discussion of the topic during and after the presentation. The speaker of the introductory presentation facilitated the discussion. There were six topics that were treated in stand-alone sessions of working group C. In addition, there were two joint sessions, one with working group B, which included one topic, and one with working group C, which included two topics. The presentations that were given in the joint sessions are summarized in the working group summary reports for groups B and D, respectively. This summary will only discuss the topics that were addressed in the stand-alone sessions, including Start-To-End Simulations, SASE Experiment, PERSEO, ''Optics Free'' FEL Oscillators, and VISA II.

  4. High-Gain High-Field Fusion Plasma

    PubMed Central

    Li, Ge

    2015-01-01

    A Faraday wheel (FW)—an electric generator of constant electrical polarity that produces huge currents—could be implemented in an existing tokamak to study high-gain high-field (HGHF) fusion plasma, such as the Experimental Advanced Superconducting Tokamak (EAST). HGHF plasma can be realized in EAST by updating its pulsed-power system to compress plasma in two steps by induction fields; high gains of the Lawson trinity parameter and fusion power are both predicted by formulating the HGHF plasma. Both gain rates are faster than the decrease rate of the plasma volume. The formulation is checked by earlier ATC tests. Good agreement between theory and tests indicates that scaling to over 10 T at EAST may be possible by two-step compressions with a compression ratio of the minor radius of up to 3. These results point to a quick new path of fusion plasma study, i.e., simulating the Sun by EAST. PMID:26507314

  5. A high-power picosecond Nd:YAG/CO{sub 2} laser system for electron guns, laser acceleration and FEL

    SciTech Connect

    Babzien, M.; Ben-Zvi, I.; Fisher, A.S.; Kusche, K.; Pogorelsky, I.V.; Srinivasan-Rao, T.

    1994-12-31

    Fourth-harmonic Nd:YAG pulses illuminating a microwave linear accelerator`s photoinjector generates electron bunches in trains for FEL experiments, or in a single pulse for laser acceleration. A multi-gigawatt CO{sub 2} laser switched by the ND:YAG fundamental delivers 50-ps pulses for Inverse Cherenkov, Inverse FEL, or Grating Linac electron acceleration experiments.

  6. Progress with FEL-based coherent electron cooling

    SciTech Connect

    Litvinenko,V.; Ben-Zvi, I.; Blaskiewicz, M.; Hao, Y.; Kayran, D.; Pozdeyev, E.; Wang, G.; Bell, G.; Bruhwiler, D.; Sobol, A.; Shevchenko, O.; Vinokurov, N.A.; Derbenev, Y.; Reiche, S.

    2008-08-24

    Cooling intense high-energy hadron beams remains a major challenge for accelerator physics. Synchrotron radiation is too feeble, while efficiency of two other cooling methods falls rapidly either at high bunch intensities (i.e. stochastic cooling of protons) or at high energies (i.e. e-cooling). The possibility of coherent electron cooling, based on high-gain FEL and ERL, was presented at last FEL conference [1]. This scheme promises significant increases in luminosities of modern high-energy hadron and electron-hadron colliders, such as LHC and eRHIC. In this paper we report progress made in the past year on the development of this scheme of coherent electron cooling (CeC), results of analytical and numerical evaluation of the concept as well our prediction for LHC and RHIC. We also present layout for proof-of-principle experiment at RHIC using our R&D ERL which is under construction.

  7. Stochastic Temporal Properties of the SASE FEL

    SciTech Connect

    Krinsky, S.

    2009-08-23

    We review the statistical description of the chaotic time evolution of the radiation from a self-amplified spontaneous-emission free-electron laser in the linear region before saturation. A high-gain, self-amplified spontaneous-emission (SASE) free-electron laser (FEL) [1, 2], based on modern beam technology, has the advantage of operating without a resonator and hence is capable of generating coherent radiation with wavelength down to the x-ray region. The LCLS at SLAC has recently achieved high gain and saturation at 1.5 {angstrom} [3]. A review of SASE theory can be found in ref. [4]. In this paper, we have considered the linear regime before saturation. In the nonlinear saturation regime, SASE is no longer a Gaussian process and analytic treatment is very difficult. A valuable numerical simulation analysis of the statistical behavior in the nonlinear regime can be found in ref. [10,11].

  8. Simulations of the LANL regenerative amplifier FEL

    SciTech Connect

    Kesselring, M.; Colson, W.B.; Wong, R.K.; Sheffield, R.L.

    1997-08-01

    The LANL regenerative amplifier FEL is designed to produce an average output power of 1 kW. Simulations study the transverse effects due to guiding by the intense electron beam and feedback. These simulations coupled with experimental measurements can be used to improve future high-power FEL designs.

  9. High gain durable anti-reflective coating

    DOEpatents

    Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze'ev R.

    2016-07-26

    Disclosed herein are polysilsesquioxane-based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In one embodiment, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, thermal radical initiator, photo radical initiators, crosslinkers, Si--OH condensation catalyst and nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

  10. Stacking nonenzymatic circuits for high signal gain

    PubMed Central

    Chen, Xi; Briggs, Neima; McLain, Jeremy R.; Ellington, Andrew D.

    2013-01-01

    Signal amplification schemes that do not rely on protein enzymes show great potential in areas as abstruse as DNA computation and as applied as point-of-care molecular diagnostics. Toehold-mediated strand displacement, a programmable form of dynamic DNA hybridization, can be used to design powerful amplification cascades that can achieve polynomial or exponential amplification of input signals. However, experimental implementation of such amplification cascades has been severely hindered by circuit leakage due to catalyst-independent side reactions. In this study, we systematically analyzed the origins, characteristics, and outcomes of circuit leakage in amplification cascades and devised unique methods to obtain high-quality DNA circuits that exhibit minimal leakage. We successfully implemented a two-layer cascade that yielded 7,000-fold signal amplification and a two-stage, four-layer cascade that yielded upward of 600,000-fold signal amplification. Implementation of these unique methods and design principles should greatly empower molecular programming in general and DNA-based molecular diagnostics in particular. PMID:23509255

  11. SASE FEL Polarization Control Using Crossed Undulator

    SciTech Connect

    Ding, Yuantao; Huang, Zhirong; /SLAC

    2008-09-30

    There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. In this paper, we study the crossed undulator scheme for rapid polarization control in a self-amplified spontaneous emission (SASE) free electron laser (FEL). Because a SASE source is a temporally chaotic light, we perform a statistical analysis on the state of polarization using FEL theory and simulations. We show that by adding a small phase shifter and a short (about 1.3 times the FEL power gain length), 90{sup o} rotated planar undulator after the main SASE planar undulator, one can obtain circularly polarized light--with over 80% polarization--near the FEL saturation.

  12. On a theory of an FEL oscillator with multicomponent undulator

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    1995-12-31

    Some novel results of a theory of an FEL oscillator with multicomponent undulator are presented. Two popular FEL oscillator configuration are under consideration: optical klystron and FEL oscillator with a prebuncher and tapered main undulator. Using similarity techniques, universal formulae and plots are obtained which allow one to calculate the FEL oscillator lasing conditions an output parameters at saturation. A one-dimensional analysis of an FEL oscillator with a linear undulator tapering is presented. Some principally novel results have been obtained. The origin of these results is in principal difference between the FEL oscillator and an FEL amplifier. In the case of the FEL amplifier the frequency of the amplified wave and all the other parameters are defined by an experimenter. Contrary to this, the case of the FEL oscillator with tapered undulator is more complicated. The lasing frequency is defined by the maximum of the small-signal gain and depends on the tapering depth in some complex way. In particular, at smooth increasing of the tapering depth, the lasing frequency may change by a leap and lasing occurs at another local maximum of the gain curve. This effect influences significantly on the FEL oscillator operation at saturation. As a result, generally accepted method of undulator tapering (for instance, by decreasing undulator field at fixed period) provides an efficiency increase only in a narrow range of the parameters of tapering. We show that in some cases, so called {open_quotes}negative tapering{close_quotes} (for instance, by increasing undulator field at fixed period) has a benefit against traditional tapering method. Ignoring of these basic features of the FEL oscillator with the tapered undulator have led many FEL research groups to nonoptimal design of the FEL experiments and incorrect interpretation of the obtained results.

  13. An output amplitude configurable wideband automatic gain control with high gain step accuracy

    NASA Astrophysics Data System (ADS)

    Xiaofeng, He; Taishan, Mo; Chengyan, Ma; Tianchun, Ye

    2012-02-01

    An output amplitude configurable wideband automatic gain control (AGC) with high gain step accuracy for the GNSS receiver is presented. The amplitude of an AGC is configurable in order to cooperate with baseband chips to achieve interference suppression and be compatible with different full range ADCs. And what's more, the gain-boosting technology is introduced and the circuit is improved to increase the step accuracy. A zero, which is composed by the source feedback resistance and the source capacity, is introduced to compensate for the pole. The AGC is fabricated in a 0.18 μm CMOS process. The AGC shows a 62 dB gain control range by 1 dB each step with a gain error of less than 0.2 dB. The AGC provides 3 dB bandwidth larger than 80 MHz and the overall power consumption is less than 1.8 mA, and the die area is 800 × 300 μm2.

  14. Computer simulation of space station computer steered high gain antenna

    NASA Technical Reports Server (NTRS)

    Beach, S. W.

    1973-01-01

    The mathematical modeling and programming of a complete simulation program for a space station computer-steered high gain antenna are described. The program provides for reading input data cards, numerically integrating up to 50 first order differential equations, and monitoring up to 48 variables on printed output and on plots. The program system consists of a high gain antenna, an antenna gimbal control system, an on board computer, and the environment in which all are to operate.

  15. EXPERIMENTAL CHARACTERIZATION OF SEEDED FEL AMPLIFIER AT THE NSLS SDL.

    SciTech Connect

    WATANABE, T.; LIU, D.; MURPHY, J.B.; ROSE, J.; SHAFTAN, T.; TSANG, T.; WANG, X.J.; YU, L.H.

    2005-08-21

    Experimental characterization of a near-IR FEL amplifier at the NSLS SDL is presented in this report. SASE was observed from 0.8-1 {micro}m with 5 orders of magnitude gain. We have experimentally demonstrated saturation of a laser seeded FEL amplifier and control of the FEL output by the seed laser. Nonlinear harmonics have also been explored. The FEL pulse length for the first three harmonics was experimentally characterized and the increase of the FEL pulse length with harmonic number was observed for the first time. Computer simulation confirmed that the observed wide spectrum of the laser seeded FEL is due to the positive chirp of the seed laser.

  16. Optical Klystron Enhancement to SASE X-ray FELs

    SciTech Connect

    Ding, Yuantao; Emma, Paul; Huang, Zhirong; Kumar, Vinit

    2006-04-07

    The optical klystron enhancement to self-amplified spontaneous emission (SASE) free electron lasers (FELs) is studied in theory and in simulations. In contrast to a seeded FEL, the optical klystron gain in a SASE FEL is not sensitive to any phase mismatch between the radiation and the microbunched electron beam. The FEL performance with the addition of four optical klystrons located at the undulator long breaks in the Linac Coherent Light Source (LCLS) shows significant improvement if the uncorrelated energy spread at the undulator entrance can be controlled to a very small level. In addition, FEL saturation at shorter x-ray wavelengths (around 1.0 A) within the LCLS undulator length becomes possible. We also discuss the application of the optical klystron in a compact x-ray FEL design that employs relatively low electron beam energy together with a shorter-period undulator.

  17. Studies of high-gain microchannel plate photomultipliers

    SciTech Connect

    Oba, K.; Rehak, P.

    1980-01-01

    The characteristics and performance of several kinds of high-gain micro-channel plate photomultipliers have been investigated. Special attention was directed toward (1) lifetime studies, (2) performance in the magnetic field, and (3) timing properties. Lifetime studies include separate investigations of the photocathode quantum efficiency degradation caused by ion feedback, and the deterioration of the micro-channel plate gain. The dependence of the micro-channel plate photomultiplier gain on the intensity and the direction of the magnetic field (up to 7 kGauss) is reported.

  18. Nano-engineered ultra-high-gain microchannel plates

    NASA Astrophysics Data System (ADS)

    Beaulieu, D. R.; Gorelikov, D.; de Rouffignac, P.; Saadatmand, K.; Stenton, K.; Sullivan, N.; Tremsin, A. S.

    2009-08-01

    Highly localized and very fast electron amplification of microchannel plates (MCPs) enables a large number of high-resolution and high-sensitivity detection technologies, which provide spatial and/or temporal information for each detected photon/electron/ion/neutron. Although there has been significant progress in photocathode and readout technologies the MCPs themselves have not evolved much from the technology developed several decades ago. Substantial increases in the gain of existing MCP technology have been accomplished by utilizing state-of-the-art processes developed for nano-engineered structures. The gain of treated MCPs with aspect ratio of 40:1 is reproducibly measured to reach unprecedented values of 2×10 5. This gain enhancement is shown to be stable during MCP operation. In addition, the initial experiments indicate improved stability of gain as a function of extracted charge and MCP storage conditions. We also present results from a fully independent thin-film process for manufacturing non-lead glass MCPs using engineered thin films for both the resistive and emissive layers. These substrate-independent MCPs show high gain, less gain degradation with extracted charge, and greater pore-to-pore and plate-to-plate uniformity than has been possible with conventional lead glass structures.

  19. Description of FEL3D: A three dimensional simulation code for TOK and FEL

    SciTech Connect

    Dutt, S.; Friedman, A.; Gover, A.

    1988-10-20

    FEL3D is a three dimensional simulation code, written for the purpose of calculating the parameters of coherent radiation emitted by electrons in an undulator. The program was written predominantly for simulating the coherent super-radiant harmonic frequency emission of electrons which are being bunched by an external laser beam while propagating in an undulator magnet. This super-radiant emission is to be studied in the TOK (transverse optical klystron) experiment, which is under construction in the NSLS department at Brookhaven National Laboratory. The program can also calculate the stimulated emission radiometric properties of a free electron laser (FEL) taking into account three dimensional effects. While this application is presently limited to the small gain operation regime of FEL's, extension to the high gain regime is expected to be relatively easy. The code is based on a semi-analytical concept. Instead of a full numerical solution of the Maxwell-Lorentz equations, the trajectories of the electron in the wiggler field are calculated analytically, and the radiation fields are expanded in terms of free space eigen-modes. This approach permits efficient computation, with a computation time of about 0.1 sec/electron on the BNL IBM 3090. The code reflects the important three dimensional features of the electron beam, the modulating laser beam, and the emitted radiation field. The statistical approach is based on averaging over the electron initial conditions according to a given distribution function in phase space, rather than via Monte-Carlo simulation. The present version of the program is written for uniform periodic wiggler field, but extension to nonuniform fields is straightforward. 4 figs., 5 tabs.

  20. High gain amplifiers: Power oscillations and harmonic generation

    SciTech Connect

    Dattoli, G.; Ottaviani, P. L.; Pagnutti, S.

    2007-08-01

    We discuss the power oscillations in saturated high gain free electron laser amplifiers and show that the relevant period can be written in terms of the gain length. We use simple arguments following from the solution of the pendulum equation in terms of Jacobi elliptic functions. Nontrivial effects due to nonlinear harmonic generation and inhomogeneous broadening are discussed too, as well as the saturated dynamics of short pulses.

  1. Study of the output pulse stability of a cascaded high-gain harmonic generation free-electron laser

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Feng, Chao; Gu, Qiang; Zhao, Zhentang

    2016-06-01

    Cascading stages of high-gain harmonic generation (HGHG) have been demonstrated to be a promising candidate for producing fully coherent soft X-ray radiation directly from UV seed sources. However, the large shot-to-shot output pulse energy fluctuation may still be a serious problem for its user applications. In this paper, we study the effects of various electron beam parameters jitters on the output pulse energy fluctuations of a two-stage HGHG. Theoretical calculations and intensive simulations have been performed and the results demonstrate that the relative timing jitter between the electron bunch and the seed laser pulse is mainly responsible for the large output pulse energy fluctuation. Several methods that may be helpful to improve the FEL stability have also been discussed.

  2. FULL ELECTROMAGNETIC FEL SIMULATION VIA THE LORENTZ-BOOSTED FRAME TRANSFORMATION

    SciTech Connect

    Fawley, William; Vay, Jean-Luc

    2010-08-16

    Numerical electromagnetic simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz-boosted frame. A particularly good application for calculation in a boosted frame isthat of short wavelength free-electron lasers (FELs) where a high energy electron beam with small fractional energy spread interacts with a static magnetic undulator. In the optimal boost frame (i.e., the ponderomotive rest frame), the red-shifted FEL radiation and blue-shifted undulator field have identical wavelengths and the number of required longitudinal grid cells and time-steps for fully electromagnetic simulation (relative to the laboratory frame) decrease by factors of gamma^2 each. In theory, boosted frame EM codes permit direct study of FEL problems for which the eikonal approximation for propagation of the radiation field and wiggler-period-averaging for the particle-field interaction may be suspect. We have adapted the WARP code to apply this method to several electromagnetic FEL problems including spontaneous emission, strong exponential gain in a seeded, single pass amplifier configuration, and emission from e-beams in undulators with multiple harmonic components. WARP has a standard relativistic macroparticle mover and a fully 3-D electromagnetic field solver. We discuss our boosted frame results and compare with those obtained using the ?standard? eikonal FEL simulation approach.

  3. Broadband optical gain via interference in the free electron laser: principles and proposed realizations.

    PubMed

    Rostovtsev, Y V; Kurizki, G; Scully, M O

    2001-08-01

    We propose experimentally simplified schemes of an optically dispersive interface region between two coupled free electron lasers (FELs), aimed at achieving a much broader gain bandwidth than in a conventional FEL or a conventional optical klystron composed of two separated FELs. The proposed schemes can universally enhance the gain of FELs, regardless of their design, when operated in the short pulsed regime. PMID:11497719

  4. Structure of the spontaneous emission spectra of high-{gamma} free electron lasers as measured at the Darmstadt (S-Dalinac) FEL

    SciTech Connect

    Renz, G.; Spindler, G.; Schlott, V.

    1995-12-31

    Recent spontaneous emission measurements at the Darmstadt infrared FEL indicate a relatively broad (down-shifted) spectrum with several intensity maxima. The typical features of the measured spectrum can be well reproduced by a numerical simulation comprising the 3-d electron dynamics in a realizable planar wiggler field, the spontaneous radiation according to the well-known Jackson formula, as well as the detection of the radiation with a finite aperture detector. An analytical consideration attributes the observed down-shift to the reduced Doppler up-shift of the radiation as observed under a finite angle with respect to the axis. The intensity peaks appear as a consequence of a modulation of the transverse velocity amplitudes of the electrons due to the betatron oscillation. The spectral spacing of these {open_quote}sidebands{close_quote} are roughly given by the Doppler up-shifted betatron frequency. Consequences for very high energy FELs will be discussed.

  5. Progress at the Jefferson Laboratory FEL

    SciTech Connect

    Tennant, Christopher

    2009-01-01

    As the only currently operating free electron laser (FEL) based on a CW superconducting energy recovering linac (ERL), the Jefferson Laboratory FEL Upgrade remains unique as an FEL driver. The present system represents the culmination of years of effort in the areas of SRF technology, ERL operation, lattice design, high power optics and DC photocathode gun technology. In 2001 the FEL Demo generated 2.1 kW of laser power. Following extensive upgrades, in 2006 the FEL Upgrade generated 14.3 kW of laser power breaking the previous world record. The FEL Upgrade remains a valuable testbed for studying a variety of collective effects, such as the beam breakup instability, longitudinal space charge and coherent synchrotron radiation. Additionally, there has been exploration of operation with lower injection energy and higher bunch charge. Recent progress and achievements in these areas will be presented, and two recent milestones â installation of a UV FEL and establishment of a DC gun test s

  6. ZnO nanowire UV photodetectors with high internal gain.

    PubMed

    Soci, C; Zhang, A; Xiang, B; Dayeh, S A; Aplin, D P R; Park, J; Bao, X Y; Lo, Y H; Wang, D

    2007-04-01

    ZnO nanowire (NW) visible-blind UV photodetectors with internal photoconductive gain as high as G approximately 108 have been fabricated and characterized. The photoconduction mechanism in these devices has been elucidated by means of time-resolved measurements spanning a wide temporal domain, from 10-9 to 102 s, revealing the coexistence of fast (tau approximately 20 ns) and slow (tau approximately 10 s) components of the carrier relaxation dynamics. The extremely high photoconductive gain is attributed to the presence of oxygen-related hole-trap states at the NW surface, which prevents charge-carrier recombination and prolongs the photocarrier lifetime, as evidenced by the sensitivity of the photocurrrent to ambient conditions. Surprisingly, this mechanism appears to be effective even at the shortest time scale investigated of t < 1 ns. Despite the slow relaxation time, the extremely high internal gain of ZnO NW photodetectors results in gain-bandwidth products (GB) higher than approximately 10 GHz. The high gain and low power consumption of NW photodetectors promise a new generation of phototransistors for applications such as sensing, imaging, and intrachip optical interconnects. PMID:17358092

  7. Characteristics of current filamentation in high gain photoconductive semiconductor switching

    SciTech Connect

    Zutavern, F J; Loubriel, G M; O'Malley, M W; Helgeson, W D; McLaughlin, D L; Denison, G J

    1992-01-01

    Characteristics of current filamentation are reported for high gain photoconductive semiconductor switches (PCSS). Infrared photoluminescence is used to monitor carrier recombination radiation during fast initiation of high gain switching in large (1.5 cm gap) lateral GaAs PCSS. Spatial modulation of the optical trigger, a 200--300 ps pulse width laser, is examined. Effects on the location and number of current filaments, rise time, and delay to high gain switching, minimum trigger energy, and degradation of switch contacts are presented. Implications of these measurements for the theoretical understanding and practical development of these switches are discussed. Efforts to increase current density and reduce switch size and optical trigger energy requirements are described. Results from contact development and device lifetime testing are presented and the impact of these results on practical device applications is discussed.

  8. Caustic Singularities Of High-Gain, Dual-Shaped Reflectors

    NASA Technical Reports Server (NTRS)

    Galindo, Victor; Veruttipong, Thavath W.; Imbriale, William A.; Rengarajan, Sambiam

    1991-01-01

    Report presents study of some sources of error in analysis, by geometric theory of diffraction (GTD), of performance of high-gain, dual-shaped antenna reflector. Study probes into underlying analytic causes of singularity, with view toward devising and testing practical methods to avoid problems caused by singularity. Hybrid physical optics (PO) approach used to study near-field spillover or noise-temperature characteristics of high-gain relector antenna efficiently and accurately. Report illustrates this approach and underlying principles by presenting numerical results, for both offset and symmetrical reflector systems, computed by GTD, PO, and PO/GO methods.

  9. High gain proportional rf control stability at TESLA cavities

    NASA Astrophysics Data System (ADS)

    Vogel, Elmar

    2007-05-01

    Fast proportional rf control is used as the basis for rf field regulation in actual linear accelerator projects like the international linear collider (ILC) and the European x-ray free electron laser (XFEL) based on TESLA technology. Additional control loops improve the field regulation by treating repetitive effects and compensating the beam loading. Nevertheless, the ability for high gain operation of the fast loops is desirable for the strong suppression of nonpredictive and nonrepetitive disturbances. TESLA cavities host nine fundamental modes (FMs) where only one is used for beam acceleration. The unwanted FMs have a significant influence on the proportional rf control loop stability at high gains. Within this paper, the stability of proportional rf control loops taking the FMs and digitalization effects into account will be discussed in detail together with measures enabling a significant increase of the gain values.

  10. Radiation Response of Emerging High Gain, Low Noise Detectors

    NASA Technical Reports Server (NTRS)

    Becker, Heidi N.; Farr, William H; Zhu, David Q.

    2007-01-01

    Data illustrating the radiation response of emerging high gain, low noise detectors are presented. Ionizing dose testing of silicon internal discrete avalanche photodiodes, and 51-MeV proton testing of InGaAs/InAlAs avalanche photodiodes operated in Geiger mode are discussed.

  11. On Point Designs for High Gain Fast Ignition

    SciTech Connect

    Key, M; Akli, K; Beg, F; Betti, R; Clark, D S; Chen, S N; Freeman, R R; Hansen, S; Hatchett, S P; Hey, D; King, J A; Kemp, A J; Lasinski, B F; Langdon, B; Ma, T; MacKinnon, A J; Meyerhofer, D; Patel, P K; Pasley, J; Phillips, T; Stephens, R B; Stoeckl, C; Foord, M; Tabak, M; Theobald, W; Storm, M; Town, R J; Wilks, S C; VanWoerkom, L; Wei, M S; Weber, R; Zhang, B

    2007-09-27

    Fast ignition research has reached the stage where point designs are becoming crucial to the identification of key issues and the development of projects to demonstrate high gain fast ignition. The status of point designs for cone coupled electron fast ignition and some of the issues they highlight are discussed.

  12. Best Practices for Achieving High, Rapid Reading Gains

    ERIC Educational Resources Information Center

    Carbo, Marie

    2008-01-01

    The percentage of students who read at the proficient level on the National Assessment of Educational Progress (NAEP) has not improved, and is appallingly low. In order for students to achieve high reading gains and become life-long readers, reading comprehension and reading enjoyment must be the top two goals. This article presents several…

  13. LCLS X-Ray FEL Output Performance in the Presence of Highly Time-Dependent Undulator Wakefields

    SciTech Connect

    Fawley, W.M.; Bane, K.L.F.; Emma, P.; Huang, Z.; Nuhn, H.-D.; Stupakov, G.; Reiche, S.; /UCLA

    2005-09-30

    Energy loss due to wakefields within a long undulator, if not compensated by an appropriate tapering of the magnetic field strength, can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive-wall component is the most critical and depends upon the chamber material (e.g., Cu) and its radius. Of recent interest[1] is the so-called ''AC'' component of the resistive-wall wake which can lead to strong variations on very short timescales (e.g., {approx} 20 fs). To study the expected performance of the LCLS in the presence of these wakefields, we have made an extensive series of start-to-end SASE simulations with tracking codes PARMELA and ELEGANT, and time-dependent FEL simulation codes GENESIS1.3 and GINGER. We discuss the impact of the wakefield losses upon output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation of the time-dependent wake losses obtained with a slight z-dependent taper in the undulator field. We compare the taper results to those predicted analytically[2].

  14. LCLS X-Ray FEL Output Performance in the Presence of HighlyTime-Dependent Undulator Wakefields

    SciTech Connect

    Bane, Karl L.F.; Emma, Paul; Huang, Heinz-Dieter Nuhn; Stupakov,Gennady; Fawley, William M.; Reiche, Sven

    2005-08-25

    Energy loss due to wakefields within a long undulator, if not compensated by an appropriate tapering of the magnetic field strength, can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive-wall component is the most critical and depends upon the chamber material (e.g., Cu) and its radius. Of recent interest[1] is the so-called ''AC'' component of the resistive-wall wake which can lead to strong variations on very short timescales (e.g., {approx} 20 0fs). To study the expected performance of the LCLS in the presence of these wakefields, we have made an extensive series of start-to-end SASE simulations with tracking codes PARMELA and ELEGANT, and time-dependent FEL simulation codes GENESIS1.3 and GINGER. We discuss the impact of the wakefield losses upon output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation of the time-dependent wake losses obtained with a slight z-dependent taper in the undulator field. We compare the taper results to those predicted analytically[2].

  15. A modular and compact portable mini-endstation for high-precision, high-speed fixed target serial crystallography at FEL and synchrotron sources.

    PubMed

    Sherrell, Darren A; Foster, Andrew J; Hudson, Lee; Nutter, Brian; O'Hea, James; Nelson, Silke; Paré-Labrosse, Olivier; Oghbaey, Saeed; Miller, R J Dwayne; Owen, Robin L

    2015-11-01

    The design and implementation of a compact and portable sample alignment system suitable for use at both synchrotron and free-electron laser (FEL) sources and its performance are described. The system provides the ability to quickly and reliably deliver large numbers of samples using the minimum amount of sample possible, through positioning of fixed target arrays into the X-ray beam. The combination of high-precision stages, high-quality sample viewing, a fast controller and a software layer overcome many of the challenges associated with sample alignment. A straightforward interface that minimizes setup and sample changeover time as well as simplifying communication with the stages during the experiment is also described, together with an intuitive naming convention for defining, tracking and locating sample positions. The setup allows the precise delivery of samples in predefined locations to a specific position in space and time, reliably and simply. PMID:26524301

  16. A modular and compact portable mini-endstation for high-precision, high-speed fixed target serial crystallography at FEL and synchrotron sources

    PubMed Central

    Sherrell, Darren A.; Foster, Andrew J.; Hudson, Lee; Nutter, Brian; O’Hea, James; Nelson, Silke; Paré-Labrosse, Olivier; Oghbaey, Saeed; Miller, R. J. Dwayne; Owen, Robin L.

    2015-01-01

    The design and implementation of a compact and portable sample alignment system suitable for use at both synchrotron and free-electron laser (FEL) sources and its performance are described. The system provides the ability to quickly and reliably deliver large numbers of samples using the minimum amount of sample possible, through positioning of fixed target arrays into the X-ray beam. The combination of high-precision stages, high-quality sample viewing, a fast controller and a software layer overcome many of the challenges associated with sample alignment. A straightforward interface that minimizes setup and sample changeover time as well as simplifying communication with the stages during the experiment is also described, together with an intuitive naming convention for defining, tracking and locating sample positions. The setup allows the precise delivery of samples in predefined locations to a specific position in space and time, reliably and simply. PMID:26524301

  17. A modular and compact portable mini-endstation for high-precision, high-speed fixed target serial crystallography at FEL and synchrotron sources

    SciTech Connect

    Sherrell, Darren A.; Foster, Andrew J.; Hudson, Lee; Nutter, Brian; O'Hea, James; Nelson, Silke; Paré-Labrosse, Olivier; Oghbaey, Saeed; Miller, R. J. Dwayne; Owen, Robin L.

    2015-10-06

    The design and implementation of a compact and portable sample alignment system suitable for use at both synchrotron and free-electron laser (FEL) sources and its performance are described. The system provides the ability to quickly and reliably deliver large numbers of samples using the minimum amount of sample possible, through positioning of fixed target arrays into the X-ray beam. The combination of high-precision stages, high-quality sample viewing, a fast controller and a software layer overcome many of the challenges associated with sample alignment. A straightforward interface that minimizes setup and sample changeover time as well as simplifying communication with the stages during the experiment is also described, together with an intuitive naming convention for defining, tracking and locating sample positions. The setup allows the precise delivery of samples in predefined locations to a specific position in space and time, reliably and simply.

  18. A modular and compact portable mini-endstation for high-precision, high-speed fixed target serial crystallography at FEL and synchrotron sources

    DOE PAGESBeta

    Sherrell, Darren A.; Foster, Andrew J.; Hudson, Lee; Nutter, Brian; O'Hea, James; Nelson, Silke; Pare-Labrosse, Olivier; Oghbaey, Saeed; Miller, R. J. Dwayne; Owen, Robin L.

    2015-01-01

    The design and implementation of a compact and portable sample alignment system suitable for use at both synchrotron and free-electron laser (FEL) sources and its performance are described. The system provides the ability to quickly and reliably deliver large numbers of samples using the minimum amount of sample possible, through positioning of fixed target arrays into the X-ray beam. The combination of high-precision stages, high-quality sample viewing, a fast controller and a software layer overcome many of the challenges associated with sample alignment. A straightforward interface that minimizes setup and sample changeover time as well as simplifying communication with themore » stages during the experiment is also described, together with an intuitive naming convention for defining, tracking and locating sample positions. Lastly, the setup allows the precise delivery of samples in predefined locations to a specific position in space and time, reliably and simply.« less

  19. A modular and compact portable mini-endstation for high-precision, high-speed fixed target serial crystallography at FEL and synchrotron sources

    SciTech Connect

    Sherrell, Darren A.; Foster, Andrew J.; Hudson, Lee; Nutter, Brian; O'Hea, James; Nelson, Silke; Pare-Labrosse, Olivier; Oghbaey, Saeed; Miller, R. J. Dwayne; Owen, Robin L.

    2015-01-01

    The design and implementation of a compact and portable sample alignment system suitable for use at both synchrotron and free-electron laser (FEL) sources and its performance are described. The system provides the ability to quickly and reliably deliver large numbers of samples using the minimum amount of sample possible, through positioning of fixed target arrays into the X-ray beam. The combination of high-precision stages, high-quality sample viewing, a fast controller and a software layer overcome many of the challenges associated with sample alignment. A straightforward interface that minimizes setup and sample changeover time as well as simplifying communication with the stages during the experiment is also described, together with an intuitive naming convention for defining, tracking and locating sample positions. Lastly, the setup allows the precise delivery of samples in predefined locations to a specific position in space and time, reliably and simply.

  20. Ultra-high gain diffusion-driven organic transistor

    NASA Astrophysics Data System (ADS)

    Torricelli, Fabrizio; Colalongo, Luigi; Raiteri, Daniele; Kovács-Vajna, Zsolt Miklós; Cantatore, Eugenio

    2016-02-01

    Emerging large-area technologies based on organic transistors are enabling the fabrication of low-cost flexible circuits, smart sensors and biomedical devices. High-gain transistors are essential for the development of large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show a new organic field-effect transistor architecture with a gain larger than 700. This is the highest gain ever reported for organic field-effect transistors. In the proposed organic field-effect transistor, the charge injection and extraction at the metal-semiconductor contacts are driven by the charge diffusion. The ideal conditions of ohmic contacts with negligible contact resistance and flat current saturation are demonstrated. The approach is general and can be extended to any thin-film technology opening unprecedented opportunities for the development of high-performance flexible electronics.

  1. Ultra-high gain diffusion-driven organic transistor

    PubMed Central

    Torricelli, Fabrizio; Colalongo, Luigi; Raiteri, Daniele; Kovács-Vajna, Zsolt Miklós; Cantatore, Eugenio

    2016-01-01

    Emerging large-area technologies based on organic transistors are enabling the fabrication of low-cost flexible circuits, smart sensors and biomedical devices. High-gain transistors are essential for the development of large-scale circuit integration, high-sensitivity sensors and signal amplification in sensing systems. Unfortunately, organic field-effect transistors show limited gain, usually of the order of tens, because of the large contact resistance and channel-length modulation. Here we show a new organic field-effect transistor architecture with a gain larger than 700. This is the highest gain ever reported for organic field-effect transistors. In the proposed organic field-effect transistor, the charge injection and extraction at the metal–semiconductor contacts are driven by the charge diffusion. The ideal conditions of ohmic contacts with negligible contact resistance and flat current saturation are demonstrated. The approach is general and can be extended to any thin-film technology opening unprecedented opportunities for the development of high-performance flexible electronics. PMID:26829567

  2. A helical optical for circular polarized UV-FEL project at the UVSOR

    SciTech Connect

    Hama, Hiroyuki

    1995-12-31

    Most of existing storage ring free electron lasers (SRFEL) are restricted those performances by degradation of mirrors in optical cavities. In general, the SRFEL gain at the short wavelength region with high energy electrons is quite low, and the high reflectivity mirrors such as dielectric multilayer mirrors are therefore required. The mirror degradation is considered as a result of irradiation of higher harmonic photons that are simultaneously emitted from planar optical klystron (OK) type undulators, which are commonly used in SRFEL. This problem is getting severer as the lasing wavelength becomes shorter. The UVSOR-FEL had been originally scheduled to be shutdown by 1996 because another undulator project for spectroscopic studies with circular polarized photon would take the FEL`s place. According to suggestion of the insertion device group of the SPring-8, we have designed a helical undulator that is able to vary degree and direction of the polarization easily. In addition, the undulator can be converted into a helical OK by replacing magnets at the center part of undulator in order to coexist with further FEL experiments. Using a calculated magnetic field for magnet configurations of the OK mode, the radiation spectrum at wide wavelength range was simulated by a Fourier transform of Lienard-Wiechert potentials. As a matter of course, some higher harmonics are radiated on the off-axis angle. However it was found out that the higher harmonics is almost negligible as far as inside a solid angle of the Gaussian laser mode. Moreover the gain at the UV region of 250 nm is expected to be much higher than our present FEL because of high brilliant fundamental radiation. The calculated spatial distribution of higher harmonics and the estimated instantaneous gain is presented. Advantages of the helical OK for SRFEL will be discussed in view of our experience, and a possibility of application two-color experiment with SR will be also mentioned.

  3. Two FEL`s in one

    SciTech Connect

    Epp, V.; Nikitin, M.

    1995-12-31

    A new scheme for a FEL operation is proposed. The conventional principle of FEL operation is means that the electron bunch passes through the interaction area of FEL only in one direction. We suggest another possible layout which implies that the electron bunch makes a turn after leaving the wiggler and entries the wiggler at the same end. Actually the wiggler is a kind of a bridge between two storage rings. The electron bunches on the orbit are expected to be adjusted in the way that after one of them leaves the wiggler, another one enters in the opposite direction and in the proper phase with the wave pulse emitted by the previous bunch. So the electron bunch comes in interaction with the amplified electromagnetic wave in both directions i.e. twice per period. It is especially important for the short wavelength FELs, because each reflection from the mirror causes a significant losses of the wave magnitude. The proposed design gives one interaction per each reflection instead of one interaction per two reflections in the traditional scheme. Another way to realize the suggested principle of operating is to insert the wiggler in the electron-positron storage ring. But this layout can be less efficient because of low intensity of the positron beam. The comparison study of radiation from different types of described double wigglers is fulfilled. The synchronization problems are discussed in this paper.

  4. Concepts for UV-FEL optics

    SciTech Connect

    Johnson, E.D.

    1993-11-01

    Brookhaven National Laboratory has developed a design for an ultra-violet free electron laser facility utilizing a seeded amplifier approach. Since the accelerator is a single pass device, resonator and outcoupler mirrors which are a difficult aspect of oscillator FEL designs are not required. The result is a source of high peak power VUV radiation with the mode structure, bandwidth and frequency stability of the input seed laser. The accelerator provides pulses of radiation at up to 10 kHz, so to maximize the utilization of the source, novel optical systems to share the radiation had to be developed. These include specialized alignment, beam transport, order sorting, and multiplexing optics. In addition, FEL on FEL pump-probe experiments are made possible by a variable optical delay of up to 10 ns operating in the wavelength range of 200 to 75 nm. Some aspects of the FEL design are also described to clarify the constraints and choices for the optical system.

  5. Three-dimensional simulation of a hole-coupled FEL oscillator

    SciTech Connect

    Krishnagopal, S.; Xie, M.; Kim, K.J.; Sessler, A.

    1991-08-01

    The performance of a two-mirror resonator with holes for out-coupling has been examined in a previous study in which the FEL gain was neglected, but the geometrical effect of the wiggler aperture was included in the optical calculation. The phenomenon of mode degeneracy was found to occur, that has serious implications for the stability of performance when the FEL gain is included. We have developed a FEL oscillator code based on TDA'', a three-dimensional FEL amplifier code, to study the mode characteristics in the presence of an FEL. We find that the interaction of the radiation and the FEL has an important, and positive, impact on the mode-profile and related cavity performance parameters. In particular, mode degeneracy is not expected to be a serious problem for reasonable FEL oscillator designs. 8 refs., 4 figs., 1 tab.

  6. Influence of electron beam halos on the FEL performance

    NASA Astrophysics Data System (ADS)

    Faatz, B.; Reiche, S.

    1999-06-01

    For single-pass free-electron lasers (FEL), such as amplifiers and SASE devices, saturation of the radiation power has to be reached within the length of the undulator. Therefore, detailed knowledge of electron beam parameters is crucial. So far, simulations have been performed with a given rms emittance and energy spread. At short radiation wavelengths, bunch compressors are used to compress the electron beam to achieve the desired high peak currents. In addition, external focusing along the entire undulator is used to maintain a constant small radius. The rotation of phase space due to compression might lead to a significant part of the bunch in tails that could increase the gain length. Furthermore, it is in general not possible to match both the beam core and the tail to the focusing structure. In this contribution, the influence of these tails, both transverse and in energy, on the FEL performance will be investigated. Simulations will be performed for beam parameters that have been assumed for the TESLA Test Facility FEL at DESY.

  7. Short wavelength FELs using the SLAC linac

    NASA Astrophysics Data System (ADS)

    Winick, H.; Bane, K.; Boyce, R.; Cobb, J.; Loew, G.; Morton, P.; Nuhn, H.-D.; Paterson, J.; Pianetta, P.; Raubenheimer, T.; Seeman, J.; Tatchyn, R.; Vylet, V.; Pellegrini, C.; Rosenzweig, J.; Travish, G.; Prosnitz, D.; Scharlemann, E. T.; Halbach, K.; Kim, K.-J.; Schlueter, R.; Xie, M.; Bonifacio, R.; De Salvo, L.; Pierini, P.

    1994-08-01

    Recent technological developments have opened the possibility to construct a device which we call a linac coherent light source (LCLS) (C. Pellegrini et al., Nucl. Instr. and Meth. A 331 (1993) 223; H. Winick et al., Proc. IEEE 1993 Particle Accelerator Conf., Washington, DC, May 1993; C. Pellegrini, Nucl. Instr. and Meth. A 341 (1994) 326; J. Seeman, SPIE Meet. on Electron Beam Sources of High Brightness Radiation, San Diego, CA, July 1993 [1-4]); it would be a fourth-generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much shorter wavelength than the 240 nm that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3 to 100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high-energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low-gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by self-amplified-spontaneous-emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops (M. Cornacchia and H. Winick (eds.), SLAC Report 92/02; I. Ben-Zvi and H. Winick (eds.), BNL report 49651 [5,6]). The required low-emittance electron beam can be achieved with recently-developed rf photocathode electron guns (B.E. Carlsten, Nucl. Instr. and Meth. A 285 (1989) 313; J. Rosenzweig and L. Serafini, Proc. IEEE 1993 Particle Accelerator Conf., Washington, DC, 1993 [7,8]). The peak current is increased by about an

  8. Cathode driven high gain crossed-field amplifier

    NASA Astrophysics Data System (ADS)

    1983-07-01

    The objective of this three-phase program is to achieve the design of a cathode driven high gain re-entrant Crossed Field Amplifier capable of meeting the parameters of Raytheon Company specification No. 968838 dated 10 May 1978. The effort includes the fabrication and test of three developmental and four final configuration tubes. One final configuration tube will be life tested and two will be delivered to the Navy. The tasks discussed during this report period relate to the cold tests performed on various subassemblies of model no. 4 and on the sealed-in model no. 4 of the S-band high gain cathode driven crossed field amplifier. Based on the performance of model no. 3 certain remedial measures have been implemented in model no. 4 that have resulted in the elimination of key resonances within the tube and an improvement in the isolation between the cathode and anode circuits.

  9. The BESSY FEL project

    NASA Astrophysics Data System (ADS)

    Abo-Bakr, M.; Anders, W.; Bahrdt, J.; Bakker, R. J.; Eberhardt, W.; Faatz, B.; Follath, R.; Gaupp, A.; von Hartrott, M.; Jaeschke, E.; Krämer, D.; Kuske, P.; Martin, M.; Müller, R.; Prange, H.; Reiche, S.; Sandner, W.; Senf, F.; Will, I.; Wüstefeld, G.

    2002-05-01

    Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung (BESSY) plans to construct a linac-based single-pass FEL as an addition to its existing third generation storage-ring-based light-source. The project aims to obtain an FEL-based user-facility that covers the VUV and soft X-ray spectral range (20 eV⩽ℏ ω⩽1 keV). At present, the design stage is funded as a collaboration between BESSY, DESY, the Hahn-Meitner-Institute in Berlin, and the Max-Born-Institute in Berlin. This stage focuses on optimization of the FEL as a user light-source, both with respect to its capabilities and in its performance. Important issues are: stability, seeding options of the SASE FEL, wavelength-tunability, synchronization with external laser sources and, on a longer time-scale, the generation of ultra-short (<20 fs RMS) optical pulses.

  10. Design issues for a laboratory high gain fusion facility

    SciTech Connect

    Hogan, W.J.

    1987-11-02

    In an inertial fusion laboratory high gain facility, experiments will be carried out with up to 1000 MJ of thermonuclear yield. The experiment area of such a facility will include many systems and structures that will have to operate successfully in the difficult environment created by the sudden large energy release. This paper estimates many of the nuclear effects that will occur, discusses the implied design issues and suggests possible solutions so that a useful experimental facility can be built. 4 figs.

  11. High gain preamplifier based on optical parametric amplification

    DOEpatents

    Jovanovic, Igor; Bonner, Randal A.

    2004-08-10

    A high-gain preamplifier based on optical parametric amplification. A first nonlinear crystal is operatively connected to a second nonlinear crystal. A first beam relay telescope is operatively connected to a second beam relay telescope, to the first nonlinear crystal, and to the second nonlinear crystal. A first harmonic beamsplitter is operatively connected to a second harmonic beamsplitter, to the first nonlinear crystal, to the second nonlinear crystal, to the first beam relay telescope, and to the second beam relay telescope.

  12. Ther FERMI FEL project at TRIESTE

    SciTech Connect

    Walker, R.P.; Bulfone, D.; Cargnello, F.

    1995-12-31

    The goal of the FERMI project - Free Electron Radiation and Matching Instrumentation - is to construct a new user facility for FEL radiation beams covering a broad spectral range (2-250 {mu}m) to complement the high brightness VUV/Soft-Xray radiation available from the ELETTRA synchrotron radiation facility at Trieste. A unique feature of the project will be the possibility of carrying out {open_quote}pump-probe{close_quote} experiments using synchronized radiation beams from FERMI and ELETTRA on the same sample. The project was launched at a meeting with Italian FEL experts held in Trieste on the 18th November 1994, chaired by C. Rubbia, as a collaboration between Sincrotrone Trieste, ENEA (Frascati), INFN (Frascati) and the University of Naples (Department of Electronic Engineering). The facility will make use of an existing linac, that forms part of the ELETTRA injection system, and a hall into which the beam can be extracted. In addition, for the first phase of the project equipment will be used from the suspended INFN/ENEA {open_quote}SURF{close_quote} FEL experiment, including the undulator, beam transport magnets and optical cavity. In this first International FEL Conference report on the project, we summarize the main features of the project, concentrating in particular on the most recent activities, including: results of measurements of the linac beam in the FEL mode of operation, further studies of the electron beam transport system including possibilities for bunch length manipulations, and further numerical calculations of the FEL performance.

  13. High resolution BPMS with integrated gain correction system

    SciTech Connect

    Wendt, M.; Briegel, C.; Eddy, N.; Fellenz, B.; Gianfelice, E.; Prieto, P.; Rechenmacher, R.; Voy, D.; Terunuma, N.; Urakawa, J.; /KEK, Tsukuba

    2009-08-01

    High resolution beam position monitors (BPM) are an essential tool to achieve and reproduce a low vertical beam emittance at the KEK Accelerator Test Facility (ATF) damping ring. The ATF damping ring (DR) BPMs are currently upgraded with new high resolution read-out electronics. Based on analog and digital down-conversion techniques, the upgrade includes an automatic gain calibration system to correct for slow drift effects and ensure high reproducible beam position readings. The concept and its technical realization, as well as preliminary results of beam studies are presented.

  14. High Power Lasing in the IR Upgrade FEL at Jefferson Lab

    SciTech Connect

    Stephen Vincent Benson; Kevin Beard; Chris Behre; George Herman Biallas; James Boyce; David Douglas; Fred Dylla; Richard Evans; Al Grippo; Joe Gubeli; David Hardy; Carlos Hernandez-Garcia; Kevin Jordan; Lia Merminga; George Neil; Joe Preble; Michelle D. Shinn; Tim Siggins; Richard Walker; Gwyn Williams; Byung Yunn; Shukui Zhang

    2004-08-01

    We report on progress in commissioning the IR Upgrade facility at Jefferson Lab. Operation at high power has been demonstrated at 5.7 microns with over 8.5 kW of continuous power output, 10 kW for 1 second long pulses, and CW recirculated electron beam power of over 1.1 MW. We report on the features and limitations of the present design and report on the path to getting even higher powers.

  15. Innovative uses of X-ray FEL and the pulsed magnets: High magnetic field X-ray scattering studies on quantum materials

    NASA Astrophysics Data System (ADS)

    Jang, H.; Nojiri, H.; Gerber, S.; Lee, W.-S.; Zhu, D.; Lee, J.-S.; Kao, C.-C.

    X-ray scattering under high magnetic fields provides unique opportunities for solving many scientific puzzles in quantum materials, such as strongly correlated electron systems. Incorporating high magnetic field capability presents serious challenges at an x-ray facility, including the limitation on the maximum magnetic field even with a DC magnet (up to ~20 Tesla), expensive cost in development, radiation damage, and limited flexibility in the experimental configuration. These challenges are especially important when studying the symmetry broken state induced by the high magnetic field are necessary, for example, exploring intertwined orders between charge density wave (CDW) and high Tc superconductivity. Moreover, a gap in magnetic field strengths has led to many discrepancies and puzzling issues for understanding strongly correlated systems - is a CDW competing or more intimately intertwined with high-temperature superconductivity. To bridge this gap and resolve these experimental discrepancies, one needs an innovative experimental approach. Here, we will present a new approach to x-ray scattering under high magnetic field up to 28 Teals by taking advantage of brilliant x-ray free electron laser (FEL). The FEL generates sufficiently high photon flux for single shot x-ray scattering experiment. In this talk, we will also present the first demonstration about the field induced CDW order in YBCO Ortho-VIII with 28 Tesla, which show the totally unexpected three-dimensional behavior.

  16. THE SECOND STAGE OF FERMI@ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE

    SciTech Connect

    Allaria, E.; DeNinno, G.; Fawley, W. M.

    2009-08-14

    The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.

  17. Filamentation effect in a gas attenuator for high-repetition-rate X-ray FELs.

    PubMed

    Feng, Yiping; Krzywinski, Jacek; Schafer, Donald W; Ortiz, Eliazar; Rowen, Michael; Raubenheimer, Tor O

    2016-01-01

    A sustained filamentation or density depression phenomenon in an argon gas attenuator servicing a high-repetition femtosecond X-ray free-electron laser has been studied using a finite-difference method applied to the thermal diffusion equation for an ideal gas. A steady-state solution was obtained by assuming continuous-wave input of an equivalent time-averaged beam power and that the pressure of the entire gas volume has reached equilibrium. Both radial and axial temperature/density gradients were found and describable as filamentation or density depression previously reported for a femtosecond optical laser of similar attributes. The effect exhibits complex dependence on the input power, the desired attenuation, and the geometries of the beam and the attenuator. Time-dependent simulations were carried out to further elucidate the evolution of the temperature/density gradients in between pulses, from which the actual attenuation received by any given pulse can be properly calculated. PMID:26698041

  18. Development of high gain avalanche photodiodes for UV imaging applications

    NASA Astrophysics Data System (ADS)

    Sood, Ashok K.; Zeller, John W.; Welser, Roger E.; Puri, Yash R.; Dupuis, Russell D.; Ji, Mi-Hee; Kim, Jeomoh; Detchprohm, Theeradetch; Dhar, Nibir K.; Lewis, Jay S.; Peters, Roy L.

    2015-08-01

    High-resolution imaging in ultraviolet (UV) bands has many applications in defense and commercial systems. The shortest wavelength is desired for increased spatial resolution, which allows for small pixels and large formats. The next frontier is to develop UV avalanche photodiode (UV-APD) arrays with high gain to demonstrate high-resolution imaging. We compare performance characteristics of front-illuminated Al0.05Ga0.95N UV-APDs grown on a free-standing (FS) GaN substrate and a GaN/sapphire template. UV-APDs grown on a FS-GaN substrate show lower dark current densities for all fabricated mesa sizes than similar UV-APDs grown on a GaN/sapphire template. In addition, stable avalanche gain higher than 5×105 and a significant increase in the responsivity of UV-APDs grown on a FS-GaN substrate are observed as a result of avalanche multiplication at high reverse bias. We believe that the high crystalline quality of Al0.05Ga0.95N UVAPDs grown on a FS-GaN substrate with low dislocation density is responsible for the observed improvement of low leakage currents, high performance photodetector characteristics, and reliability of the devices.

  19. Filamentation effect in a gas attenuator for high-repetition-rate X-ray FELs

    SciTech Connect

    Feng, Yiping; Krzywinski, Jacek; Schafer, Donald W.; Ortiz, Eliazar; Rowen, Michael; Raubenheimer, Tor O.

    2016-01-01

    A sustained filamentation or density depression phenomenon in an argon gas attenuator servicing a high-repetition femtosecond X-ray free-electron laser has been studied using a finite-difference method applied to the thermal diffusion equation for an ideal gas. A steady-state solution was obtained by assuming continuous-wave input of an equivalent time-averaged beam power and that the pressure of the entire gas volume has reached equilibrium. Both radial and axial temperature/density gradients were found and describable as filamentation or density depression previously reported for a femtosecond optical laser of similar attributes. The effect exhibits complex dependence on the input power, the desired attenuation, and the geometries of the beam and the attenuator. Time-dependent simulations were carried out to further elucidate the evolution of the temperature/density gradients in between pulses, from which the actual attenuation received by any given pulse can be properly calculated.

  20. Properties of the ultrashort gain length, self-amplified spontaneous emission free-electron laser in the linear regime and saturation

    NASA Astrophysics Data System (ADS)

    Murokh, A.; Agustsson, R.; Babzien, M.; Ben-Zvi, I.; Bertolini, L.; van Bibber, K.; Carr, R.; Cornacchia, M.; Frigola, P.; Hill, J.; Johnson, E.; Klaisner, L.; Le Sage, G.; Libkind, M.; Malone, R.; Nuhn, H.-D.; Pellegrini, C.; Reiche, S.; Rakowsky, G.; Rosenzweig, J.; Ruland, R.; Skaritka, J.; Toor, A.; Tremaine, A.; Wang, X.; Yakimenko, V.

    2003-06-01

    VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. The experiment was performed at the Accelerator Test Facility at BNL, using a high brightness 70-MeV electron beam. A gain length shorter than 18 cm has been obtained, yielding a total gain of 2×108 at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. Results are compared to the three-dimensional SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL systems. An agreement between simulations and experimental results has been obtained at an unprecedented level of detail.

  1. Dynamical aspects on FEL interaction in single passage and storage ring devices

    SciTech Connect

    Dattoli, G.; Renieri, A.

    1995-12-31

    The dynamical behaviour of the free-electron lasers is investigated using appropriate scaling relations valid for devices operating in the low and high gain regimes, including saturation. The analysis is applied to both single passage and storage ring configurations. In the latter case the interplay between the interaction of the electron bean with the laser field and with the accelerator environment is investigated. In particular we discuss the effect of FEL interaction on the microwave instability.

  2. Epitaxial design of ultra high power tunable laser gain section

    NASA Astrophysics Data System (ADS)

    Zhang, Yaping; Benson, Trevor M.

    2005-09-01

    High power widely tunable lasers are extremely desirable for telecom applications as a replacement for distributed feedback (DFB) lasers in wavelength division multiplexing (WDM) systems, due to their dynamic provision properties. They are also sought after for many other applications, such as phased radar systems, optical switching and routing. This paper introduces novel design ideas and approaches on how to achieve ultra high power in the design of an InGaAsP-InP based widely tunable laser gain section. The inventive ideas are basically composed of two parts. Firstly, to increase the facet optical output power by the inclusion of an InP spacer layer below the ridge and above the multiple quantum wells (MQWs) stack, in order to have extra freedom in the control of widening the single mode ridge width. Secondly, to reduce the free-carrier absorption loss by the inclusion of a bulk balance layer structure below the MQWs stack and above the buffer layer, so as to largely shift the optical mode distribution to the intrinsic and n-doped side of the epilayer structure where the free-carrier absorption loss is lower than that of the p-doped side. Simulation results show that the proposed epilayer designs of the ultra high power gain sections would greatly increase the facet optical output power of a tunable laser, by up to about 80%. It should be noted that these novel epilayer design ideas and approaches developed for the gain section are applicable to the designs of ultra high power DFB lasers and other InGaAsP-InP based lasers.

  3. A high gain antenna system for airborne satellite communication applications

    NASA Technical Reports Server (NTRS)

    Maritan, M.; Borgford, M.

    1990-01-01

    A high gain antenna for commercial aviation satellites communication is discussed. Electromagnetic and practical design considerations as well as candidate systems implementation are presented. An evaluation of these implementation schemes is given, resulting in the selection of a simple top mounted aerodynamic phased array antenna with a remotely located beam steering unit. This concept has been developed into a popular product known as the Canadian Marconi Company CMA-2100. A description of the technical details is followed by a summary of results from the first production antennas.

  4. High power VCSEL device with periodic gain active region

    NASA Astrophysics Data System (ADS)

    Ning, Y. Q., II; Qin, L.; Sun, Y. F.; Li, T.; Cui, J. J.; Peng, B.; Liu, G. Y.; Zhang, Y.; Liu, Y.; Wang, L. J.; Cui, D. F.; Xu, Z. Y.

    2007-11-01

    High power vertical cavity surface emitting lasers with large aperture have been fabricated through improving passivation, lateral oxidation and heat dissipation techniques. Different from conventional three quantum well structure, a periodic gain active region with nine quantum wells was incorporated into the VCSEL structure, with which high efficiency and high power operation were expected. The nine quantum wells were divided into three groups with each of them located at the antinodes of the cavity to enhance the coupling between the optical field and the gain region. Large aperture and bottom-emitting configuration was used to improve the beam quality and the heat dissipation. A maximum output power of 1.4W was demonstrated at CW operation for a 400μm-diameter device. The lasing wavelength shifted to 995.5nm with a FWHM of 2nm at a current of 4.8A due to the internal heating and the absence of active water cooling. A ring-shape farfield pattern was induced by the non-homogeneous lateral current distribution in large diameter device. The light intensity at the center of the ring increased with increasing current. A symmetric round light spot at the center and single transverse mode operation with a divergence angle of 16° were observed with current beyond 4.8A.

  5. Design study of a 7 kW, visible wavelength FEL

    SciTech Connect

    Chen, S.C.; Danly, B.G.; Temkin, R.J.; Wurtele, J.; Yang, B.

    1990-01-01

    The MIT Lincoln Laboratory is investigating the possibility of building a free electron laser (FEL) operating at an average power of about 7 kW at wavelengths of 500--600 nm. Additional specifications for the FEL include a bandwidth of less than 0.1 cm{sup {minus}1} and a micropulse separation of less than 10 ns. The design study has investigated the basic design parameters of the FEL including an analysis of the electron accelerator, beam line, wiggler and optical cavity. A nonlinear model of the FEL has been used to calculate the FEL gain and efficiency. The required output power appears achievable from an FEL operating at more than 1% efficiency with a conventional RF accelerator. Details of the FEL design are presented in this report which represent the final report for the year from September 1, 1989 to August 31, 1990. 28 refs., 13 figs., 5 tabs.

  6. Experimental Characterization of Nonlinear Harmonic Radiation from a Visible SASE FEL at Saturation

    NASA Astrophysics Data System (ADS)

    Tremaine, A.; Wang, X. J.; Babzien, M.; Ben-Zvi, I.; Cornacchia, M.

    2002-08-01

    Nonlinear harmonic radiation was observed using the VISA SASE FEL at saturation. The gain lengths, spectra and energies of the three lowest SASE FEL modes were experimentally characterized. Both the measured harmonic gain lengths and center spectral wavelengths are shown to decrease with harmonic number, n, which is consistent with nonlinear harmonic theory. The measured energies for both second and third harmonics are about 1% of the fundamental; the strong second harmonic radiation (approximately 1 microJ) observed is unique for low energy SASE FELs. These experimental results demonstrate for the first time the feasibility of using nonlinear harmonic SASE FEL radiation to produce coherent, femtosecond X-rays.

  7. Experimental Characterization of Nonlinear Harmonic Radiation from a Visible SASE FEL at Saturation

    SciTech Connect

    Cornacchia, Massimo

    2002-08-19

    Nonlinear harmonic radiation was observed using the VISA SASE FEL at saturation. The gain lengths, spectra and energies of the three lowest SASE FEL modes were experimentally characterized. Both the measured harmonic gain lengths and center spectral wavelengths are shown to decrease with harmonic number, n, which is consistent with nonlinear harmonic theory. The measured energies for both second and third harmonics are about 1% of the fundamental; the strong second harmonic radiation ({approx} 1 {micro}J) observed is unique for low energy SASE FELs. These experimental results demonstrate for the first time the feasibility of using nonlinear harmonic SASE FEL radiation to produce coherent, femtosecond X-rays.

  8. An experimental analysis of the waveguide modes in a high-gain free-electron laser amplifier

    SciTech Connect

    Anderson, B.R.

    1989-01-01

    The presence, growth, and interaction of transverse waveguide modes in high-gain free-electron laser (FEL) amplifiers has been observed and studied. Using the Electron Laser Facility at Lawrence Livermore National Laboratory, a 3 MeV, 800 A electron beam generated by the Experimental Test Accelerator was injected into a planar wiggler. Power was then extracted and measured in the fundamental (TE{sub 01}) an higher-order modes (Te{sub 21} and TM{sub 21}) under various sets of operating conditions. Horizontal focusing through the wiggler was provided by external quadrupole magnets. There was no axial guide field. The input microwave signal for amplification was generated by a 100 kW magnetron operating at 34.6 Ghz. Power measurements were taken for both flat and tapered wigglers, for two sizes of waveguide, and for both flat and tapered wigglers, for two sizes of waveguide, and for both fundamental and higher mode injection. Mode content was determined by sampling the radiated signal at specific points in the radiation patter. For the flat wiggler and with the large waveguide (2.9 cm {times} 9.8 cm) the power in the higher modes was comparable to power in the fundamental. both exhibited gains greater than 30 dB/m prior to saturation and both reached powers in excess of 80 MW. Choice of injection mode had little effect on the operation of the system. Operation with the smaller guide (WR-229) provided much better mode selectivity. The fundamental mode continued to show optimum gain in excess of 30 dB/m while the higher-mode gain was of order 20 dB/m. As expected, power output increased significantly with the tapered wigglers. The relative mode content depended on the specific taper used.

  9. Avoiding Obstructions in Aiming a High-Gain Antenna

    NASA Technical Reports Server (NTRS)

    Edmonds, Karina

    2006-01-01

    The High Gain Antenna Pointing and Obstruction Avoidance software performs computations for pointing a Mars Rover high-gain antenna for communication with Earth while (1) avoiding line-of-sight obstructions (the Martian terrain and other parts of the Rover) that would block communication and (2) taking account of limits in ranges of motion of antenna gimbals and of kinematic singularities in gimbal mechanisms. The software uses simplified geometric models of obstructions and of the trajectory of the Earth in the Martian sky(see figure). It treats all obstructions according to a generalized approach, computing and continually updating the time remaining before interception of each obstruction. In cases in which the gimbal-mechanism design allows two aiming solutions, the algorithm chooses the solution that provides the longest obstruction-free Earth-tracking time. If the communication session continues until an obstruction is encountered in the current pointing solution and the other solution is now unobstructed, then the algorithm automatically switches to the other position. This software also notifies communication- managing software to cease transmission during the switch to the unobstructed position, resuming it when the switch is complete.

  10. FEL phased array configurations

    NASA Astrophysics Data System (ADS)

    Shellan, Jeffrey B.

    1986-01-01

    The advantages and disadvantages of various phased array and shared aperture concepts for FEL configurations are discussed. Consideration is given to the characteristics of intra- and inter-micropulse phasing; intra-macropulse phasing; an internal coupled resonator configuration; and an injection locked oscillator array. The use of a master oscillator power amplifier (MOPA) configuration with multiple or single master oscillators for FELs is examined. The venetian blind, rotating plate, single grating, and grating rhomb shared aperture concepts are analyzed. It is noted that the shared aperture approach using a grating rhomb and the MOPA concept with a single master oscillator and a coupled resonator are useful for FEL phased array configurations; and the MOPA concept is most applicable.

  11. Transverse effects in UV FELs

    SciTech Connect

    Small, D.W.; Wong, R.K.; Colson, W.B.

    1995-12-31

    In an ultraviolet Free Electron Laser (UV FEL), the electron beam size can be approximately the same as the optical mode size. The performance of a UV FEL is studied including the effect of emittance, betatron focusing, and external focusing of the electron beam on the transverse optical mode. The results are applied to the Industrial Laser Consortium`s UV FEL.

  12. Performance of the KHI FEL device at FEL-SUT

    NASA Astrophysics Data System (ADS)

    Yokoyama, M.; Oda, F.; Nomaru, K.; Koike, H.; Sobajima, M.; Miura, H.; Kawai, M.; Kuroda, H.

    2002-05-01

    FEL lasing with the saturated power in the wavelength of 4-16 μm was achieved by using the KHI (Kawasaki Heavy Industries, Ltd.) FEL device. The macro-pulse length of the electron beam was improved by using the LaB 6 cathode instead of the dispenser cathode as a cathode of the OCS RF-gun. The improvement yielded the saturated FEL power with the macro-pulse length of 0.5-1.5 μs. The FEL energy was 2-40 mJ. The measured FEL output powers were in agreement with the values which were taken into account Piovella's theory.

  13. Optical tailoring of xFEL beams

    SciTech Connect

    West, Gavin; Coffee, R.

    2015-08-20

    There is an inherent exibility unique to free electron lasers (FELs) that lends well to experimental approaches normally too difficult for other light sources to accomplish. This includes the ability to optically shape the electron bunch prior to final its acceleration for the final FEL process. Optical pulse shaping of the electron bunch can enable both femtosecond and attosecond level FEL pulse control. Pulse shaping is currently implemented, not optically but mechanically, in LCLS-I with an adjustable foil slit that physically spoils the momentum phase of the electron bunch. This selectively suppresses the downstream FEL process ofspoiled electrons. Such a mechanical spoiling method fails for both the soft x-ray regime as well as the high repetition rates that are planned in LCLS-II. Our proposed optical spoiling method circumvents this limitation by making use of the existing ultrafast laser beam that is typically used for adjusting the energy spread for the initial electron bunch. Using Fourier domain shaping we can nearly arbitrarily shape the laser pulses to affect the electron bunch. This can selectively spoil electrons within each bunch. Here we demonstrate the viability of this approach with a programmable acousto-optic dispersive filter. This method is not only well suited for LCLS-II but also has several advantages over mechanical spoiling, including lack of radiation concerns, experiment specific FEL pulse shapes, and real-time adjustment for applications that require high duty-cycle variation such as lock-in amplification of small signals.

  14. Intracavity gain shaping in millijoule-level, high gain Ho:YLF regenerative amplifiers.

    PubMed

    Murari, Krishna; Cankaya, Huseyin; Kroetz, Peter; Cirmi, Giovanni; Li, Peng; Ruehl, Axel; Hartl, Ingmar; Kärtner, Franz X

    2016-03-15

    We demonstrate intracavity gain shaping inside a 2 μm Ho:YLF regenerative amplifier with a spectral bandwidth of 2.9 nm broadened to 5.4 nm, corresponding to Fourier-limited pulses of 1 ps duration. The intracavity gain shaping is achieved by using a simple etalon, which acts as a frequency-selective filter. The output of the regenerative amplifier is amplified by a single-pass amplifier, and we achieve total energy of 2.2 mJ and pulse duration of 2.4 ps at 1 kHz with pulse fluctuations <1%. The amplifier chain is seeded by a home-built mode-locked holmium-doped fiber oscillator. PMID:26977647

  15. Bunch Length Measurements at the JLab FEL Using Coherent Transition and Synchrotron Radiation

    NASA Astrophysics Data System (ADS)

    Evtushenko, P.; Coleman, J.; Jordan, K.; Klopf, J. Michael; Neil, G.; Williams, G. P.

    2006-11-01

    The JLab FEL is routinely operated with sub-picosecond bunches. The short bunch length is important for high gain of the FEL. Coherent transition radiation has been used for the bunch length measurements for many years. This diagnostic can be used only in the pulsed beam mode. It is our goal to run the FEL with CW beam and a 74.85 MHz micropulse repetition rate, which, with the 135 pC nominal bunch charge corresponds to the beam average current of 10 mA, Hence it is very desirable to have the possibility of making bunch length measurements when running CW beam with any micropulse frequency. We use a Fourier transform infrared (FTIR) interferometer, which is essentially a Michelson interferometer, to measure the spectrum of the coherent synchrotron radiation generated in the last dipole of the magnetic bunch compressor upstream of the FEL wiggler. This noninvasive diagnostic provides bunch length measurements for CW beam operation at any micropulse frequency. We also compare the measurements made with the help of the FTIR interferometer with data obtained using the Martin-Puplett interferometer. Results of the two diagnostics agree within 15 %. Here we present a description of the experimental setup, data evaluation procedure and results of the beam measurements.

  16. Users program for storage-ring based FEL and synchrotron sources of the Duke FEL Laboratory

    SciTech Connect

    Straub, K.D.; Barnett, G.; Burnham, B.

    1995-12-31

    The storage ring at the Duke FEL Laboratory was first operated with a stored e-beam in November, 1994. It has now achieved operation energies in excess 1 GeV with more than 100 mA current at 280 MeV. The ring has several ports for FEL and synchrotron light source research. The circulating ring current can be synchronized with the seperate Mark III FEL operating in the 2-9.5 {mu}m IR region. This allows low optical jitter (10-20 ps) between the two sources and thus pump-probe operation. The ring has been configured to drive a number of light sources including the OK-4 FEL system capable of FEL operation between 400 and 65 nm, an inverse Compton scattering source using this undulator which will yield 4-200 MeV gammas, an undulator source at approximately 40 {angstrom} (not an FEL), a mm FEL with inverse compton scattering providing 1-100 keV x-rays and two synchrotron ports from the bend magnets for which the {lambda}{sub c} = 11-12 {angstrom} for 1 GeV. The broadly tunable FEL sources and their associated inverse compton scattering are extremely bright. The initial research proposals, submitted to the Laboratory emphasizes photoelectron spectroscopy, PEEM, high resolution vacuum UV of gases, solid spectroscopy and photochemistry in the UV, X-ray microprobe studies, X-ray microscopy, X-ray holography, X-ray crystallography, Mossbauer spectroscopy, nuclear spectroscopy, neutron production, photon activation therapy and broadband synchrotron as a probe of fast reaction in the IR and near IR.

  17. High gain antenna pointing on the Mars Exploration Rovers

    NASA Technical Reports Server (NTRS)

    Vanelli, C. Anthony; Ali, Khaled S.

    2005-01-01

    This paper describes the algorithm used to point the high gain antennae on NASA/JPL's Mars Exploration Rovers. The gimballed antennae must track the Earth as it moves across the Martian sky during communication sessions. The algorithm accounts for (1) gimbal range limitations, (2) obstructions both on the rover and in the surrounding environment, (3) kinematic singularities in the gimbal design, and (4) up to two joint-space solutions for a given pointing direction. The algorithm computes the intercept-times for each of the occlusions and chooses the jointspace solution that provides the longest track time before encountering an occlusion. Upon encountering an occlusion, the pointing algorithm automatically switches to the other joint-space solution if it is not also occluded. The algorithm has successfully provided flop-free pointing for both rovers throughout the mission.

  18. Low-dispersion, high-gain femtosecond optical pulse amplifier.

    PubMed

    Rodenberger, D C; Grossman, C H; Garito, A F

    1990-05-01

    We demonstrate a novel amplifier for femtosecond optical pulses. The output of a colliding-pulse mode-locked laser is amplified to 0.3 microJ per pulse at a repetition rate of 8 kHz by using 1 W of pump power from a copper-vapor laser. Our high-efficiency amplifier focuses the beam for four gain passes through a thin dye stream that uses a Z configuration with matched focusing. Because of low group-velocity dispersion, the output pulses are only slightly broadened, from 63 to 73 fsec, and may be used directly to generate a white-light continuum without pulse compression after amplification. PMID:19767988

  19. Progress on achieving the ICF conditions needed for high gain

    SciTech Connect

    Lindl, J.D.

    1988-12-23

    Progress during the past two years has moved us much closer to demonstrating the scientific and technological requirements for high gain ICF in the laboratory. This progress has been made possible by operating at the third harmonic of 1..mu..m light which dramatically reduces concern about hot electrons and by advances in diagnostics such as 100 ps x-ray framing cameras which greatly increase the data available from each experiment. Making use of many of these new capabilities, major improvements in confinement conditions have been achieved for ICF implosions. In particular, in an optimized hohlraum on Nova, radiation driven implosions with convergence ratio in excess of 30 (volume compression /approximately/3 /times/ 10/sup 4/) have performed essentially as predicted by spherical implosion calculations. This paper presents these results as well as examples of advances in several other areas and discusses the implications for the future of ICF with lasers and heavy ion beam drivers. 8 refs., 10 figs.

  20. High gain GaAs photoconductive semiconductor switches: Switch longevity

    SciTech Connect

    Loubriel, G.M.; Zutavern, F.J.; Mar, A.

    1998-07-01

    Optically activated, high gain GaAs switches are being tested for many different pulsed power applications that require long lifetime (longevity). The switches have p and n contact metallization (with intentional or unintentional dopants) configured in such a way as to produce p-i-n or n-i-n switches. The longevity of the switches is determined by circuit parameters and by the ability of the contacts to resist erosion. This paper will describe how the switches performed in test-beds designed to measure switch longevity. The best longevity was achieved with switches made with diffused contacts, achieving over 50 million pulses at 10 A and over 2 million pulses at 80 A.

  1. Black Phosphorus Mid-Infrared Photodetectors with High Gain

    NASA Astrophysics Data System (ADS)

    Guo, Qiushi; Pospischil, Andreas; Bhuiyan, Maruf; Jiang, Hao; Tian, He; Farmer, Damon; Deng, Bingchen; Li, Cheng; Han, Shu-Jen; Wang, Han; Xia, Qiangfei; Ma, Tso-Ping; Mueller, Thomas; Xia, Fengnian

    2016-07-01

    Recently, black phosphorus (BP) has joined the two dimensional material family as a promising candidate for photonic applications, due to its moderate bandgap, high carrier mobility, and compatibility with a diverse range of substrates. Photodetectors are probably the most explored BP photonic devices, however, their unique potential compared with other layered materials in the mid-infrared wavelength range has not been revealed. Here, we demonstrate BP mid infrared detectors at 3.39 um with high internal gain, resulting in an external responsivity of 82 A/W. Noise measurements show that such BP photodetectors are capable of sensing low intensity mid-infrared light in the picowatt range. Moreover, the high photoresponse remains effective at kilohertz modulation frequencies, because of the fast carrier dynamics arising from BPs moderate bandgap. The high photoresponse at mid infrared wavelengths and the large dynamic bandwidth, together with its unique polarization dependent response induced by low crystalline symmetry, can be coalesced to promise photonic applications such as chip-scale mid-infrared sensing and imaging at low light levels.

  2. Black Phosphorus Mid-Infrared Photodetectors with High Gain.

    PubMed

    Guo, Qiushi; Pospischil, Andreas; Bhuiyan, Maruf; Jiang, Hao; Tian, He; Farmer, Damon; Deng, Bingchen; Li, Cheng; Han, Shu-Jen; Wang, Han; Xia, Qiangfei; Ma, Tso-Ping; Mueller, Thomas; Xia, Fengnian

    2016-07-13

    Recently, black phosphorus (BP) has joined the two-dimensional material family as a promising candidate for photonic applications due to its moderate bandgap, high carrier mobility, and compatibility with a diverse range of substrates. Photodetectors are probably the most explored BP photonic devices, however, their unique potential compared with other layered materials in the mid-infrared wavelength range has not been revealed. Here, we demonstrate BP mid-infrared detectors at 3.39 μm with high internal gain, resulting in an external responsivity of 82 A/W. Noise measurements show that such BP photodetectors are capable of sensing mid-infrared light in the picowatt range. Moreover, the high photoresponse remains effective at kilohertz modulation frequencies, because of the fast carrier dynamics arising from BP's moderate bandgap. The high photoresponse at mid-infrared wavelengths and the large dynamic bandwidth, together with its unique polarization dependent response induced by low crystalline symmetry, can be coalesced to promise photonic applications such as chip-scale mid-infrared sensing and imaging at low light levels. PMID:27332146

  3. High-Gain Avalanche Rushing amorphous Photoconductor (HARP) detector

    NASA Astrophysics Data System (ADS)

    Tanioka, K.

    2009-09-01

    We have been studying a very sensitive image sensor since the early 1980s. In 1985, the author found for the first time that an experimental pickup tube with an amorphous selenium photoconductive target exhibits high sensitivity with excellent picture quality because of a continuous and stable avalanche multiplication phenomenon. We named the pickup tube with an amorphous photoconductive layer operating in the avalanche-mode "HARP": High-gain Avalanche Rushing amorphous Photoconductor. A color camera equipped with the HARP pickup tubes has a maximum sensitivity of 11 lx at F8. This means that the HARP camera is about 100 times as sensitive as that of CCD camera for broadcasting. This ultrahigh-sensitivity HARP pickup tube is a powerful tool for reporting breaking news at night and other low-light conditions, the production of scientific programs, and numerous other applications, including medical diagnoses, biotech research, and nighttime surveillance. In addition, since the HARP target can convert X-rays into electrons directly, it should be possible to exploit this capability to produce X-ray imaging devices with unparalleled levels of resolution and sensitivity.

  4. An Experimental Study of an FEL Oscillator with a Linear Taper

    SciTech Connect

    Benson, S.; Gubeli, J.; Neil, G.R.

    2001-01-01

    Motivated by the work of Saldin, Schneidmiller and Yurkov, we have measured the detuning curve widths, spectral characteristics, efficiency, and energy spread as a function of the taper for low and high Q resonators in the IR Demo FEL at Jefferson Lab. Both positive and negative tapers were used. Gain and frequency agreed reasonably well with the predictions of a single mode theory. The efficiency agreed reasonably well for a negative taper with a high Q resonator but disagreed for lower Q values due to the large slippage parameter and the non-ideal resonator Q. We saw better efficiency for a negative taper than for the same positive taper. The energy spread induced in the beam, normalized to the efficiency is larger for the positive taper than for the corresponding negative taper. This indicates that a negative taper is preferred over a positive taper in an energy recovery FEL.

  5. PROPOSAL FOR A PRE-BUNCHED LASER WAKEFIELD ACCELERATION EXPERIMENT AT THE BNL DUV FEL FACILITY.

    SciTech Connect

    WANG,X.J.SHEEHY,B.WU,Z.GAI,W.TING,A.

    2003-05-12

    We propose a pre-bunched Laser Wakefield Acceleration (LWFA) experiment in a plasma channel at the BNL DUV-FEL Facility. BNL DUV-FEL facility is uniquely qualified to carry out the proposed experiment because of the high-brightness' electron beam and RF synchronized TW Ti:Sapphire laser system. The DUV-FEL is a 200 MeV linac facility equipped with a photocathode RF gun injector, a 100 fs Ti:Sapphire laser system and a magnetic bunch compressor. The proposed LWFA will inject a 150 MeV, 10 fs electron bunch into a centimeters long plasma channel. Simulation and preliminary experiment showed that, high-brightness 10 fs electron bunch with 20 pC charge could be produced using the technique of longitudinal emittance compensation. The initial experiment will be performed using the existing Ti:Sapphire laser system (50mJ, 100 fs) with 30 {micro}m spot and 4 cm channel, the maximum energy gain will be about 15 MeV. We propose to upgrade the existing SDL laser output to 500 mJ with a shorter pulse length (50 fs). For an electron beam spot size of 20 um, the expected energy gain is about 100 MeV for a 5 TW, 50 fs laser pulse.

  6. High-gain nonlinear observer for simple genetic regulation process

    NASA Astrophysics Data System (ADS)

    Torres, L. A.; Ibarra-Junquera, V.; Escalante-Minakata, P.; Rosu, H. C.

    2007-07-01

    High-gain nonlinear observers occur in the nonlinear automatic control theory and are in standard usage in chemical engineering processes. We apply such a type of analysis in the context of a very simple one-gene regulation circuit. In general, an observer combines an analytical differential-equation-based model with partial measurement of the system in order to estimate the non-measured state variables. We use one of the simplest observers, that of Gauthier et al., which is a copy of the original system plus a correction term which is easy to calculate. For the illustration of this procedure, we employ a biological model, recently adapted from Goodwin's old book by De Jong, in which one plays with the dynamics of the concentrations of the messenger RNA coding for a given protein, the protein itself, and a single metabolite. Using the observer instead of the metabolite, it is possible to rebuild the non-measured concentrations of the mRNA and the protein.

  7. Fast ignition integrated experiments and high-gain point design

    NASA Astrophysics Data System (ADS)

    Shiraga, H.; Nagatomo, H.; Theobald, W.; Solodov, A. A.; Tabak, M.

    2014-05-01

    Integrated fast ignition experiments were performed at ILE, Osaka, and LLE, Rochester, in which a nanosecond driver laser implodes a deuterated plastic shell in front of the tip of a hollow metal cone and an intense ultrashort-pulse laser is injected through the cone to heat the compressed plasma. Based on the initial successful results of fast electron heating of cone-in-shell targets, large-energy short-pulse laser beam lines were constructed and became operational: OMEGA-EP at Rochester and LFEX at Osaka. Neutron enhancement due to heating with a ˜kJ short-pulse laser has been demonstrated in the integrated experiments at Osaka and Rochester. The neutron yields are being analysed by comparing the experimental results with simulations. Details of the fast electron beam transport and the electron energy deposition in the imploded fuel plasma are complicated and further studies are imperative. The hydrodynamics of the implosion was studied including the interaction of the imploded core plasma with the cone tip. Theory and simulation studies are presented on the hydrodynamics of a high-gain target for a fast ignition point design.

  8. Fast ignition integrated experiments and high-gain point design

    SciTech Connect

    Shiraga, H.; Nagatomo, H.; Theobald, W.; Solodov, A. A.; Tabak, M.

    2014-04-17

    Here, integrated fast ignition experiments were performed at ILE, Osaka, and LLE, Rochester, in which a nanosecond driver laser implodes a deuterated plastic shell in front of the tip of a hollow metal cone and an intense ultrashort-pulse laser is injected through the cone to heat the compressed plasma. Based on the initial successful results of fast electron heating of cone-in-shell targets, large-energy short-pulse laser beam lines were constructed and became operational: OMEGA-EP at Rochester and LFEX at Osaka. Neutron enhancement due to heating with a ~kJ short-pulse laser has been demonstrated in the integrated experiments at Osaka and Rochester. The neutron yields are being analyzed by comparing the experimental results with simulations. Details of the fast electron beam transport and the electron energy deposition in the imploded fuel plasma are complicated and further studies are imperative. The hydrodynamics of the implosion was studied including the interaction of the imploded core plasma with the cone tip. Theory and simulation studies are presented on the hydrodynamics of a high-gain target for a fast ignition point design.

  9. High-gain reverse guide field free electron lasers

    SciTech Connect

    Tsui, K.H.

    1995-10-01

    Electron beam trajectories under circularly polarized external wigglers in free electron laser devices with axial guide fields are reconsidered by introducing the self-fields of the electron beam. The competition between the self-fields and the wiggler field plus the action of the guide field are not only responsible for the known positive guide field singularity, but also the new reverse guide field singularity. The physics of the new reverse field singularity relies on the fact that an azimuthal magnetic field uniform in {ital z} is able to generate steady-state helical beam orbits just as if it were a transverse wiggler. According to this theory, the handness of the circularly polarized microwave should depend on the guide field configuration. High-gain strong pump equations coupled to these trajectories are used to account for the Massachusetts Institute of Technology reverse guide field results [Phys. Rev. Lett. {bold 67}, 3082 (1991)]. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. Beam Conditioning for FELs: Consequences and Methods

    SciTech Connect

    Wolski, Andrzej; Penn, Gregory; Sessler, Andrew; Wurtele, Jonathan

    2003-10-09

    The consequences of beam conditioning in four example cases (VISA, a Soft X-Ray FEL, LCLS and a ''Greenfield'' FEL) are examined. It is shown that in emittance limited cases, proper conditioning reduces sensitivity to the transverse emittance, and allows stronger focusing in the undulator. Simulations show higher saturation power, with gain lengths reduced up to a factor of two. The beam dynamics in a general conditioning system are studied, with ''matching conditions'' derived for achieving conditioning without growth in effective emittance. Various conditioners are considered, and expressions derived for the amount of conditioning provided in each case when the matching conditions are satisfied. We discuss the prospects for conditioners based on laser and plasma systems.

  11. Beam conditioning for FELs: Consequences and methods

    SciTech Connect

    Wolski, A.; Penn, G.; Sessler, A.; Wurtele, J.

    2004-06-29

    The consequences of beam conditioning in four example cases (VISA, a Soft X-Ray FEL, LCLS and a ''Greenfield'' FEL) are examined. It is shown that in emittance limited cases, proper conditioning reduces sensitivity to the transverse emittance and, furthermore, allows for stronger focusing in the undulator. Simulations show higher saturation power, with gain lengths reduced by a factor of two or more. The beam dynamics in a general conditioning system are studied, with ''matching conditions'' derived for achieving conditioning without growth in the effective emittance. Various conditioning lattices are considered, and expressions derived for the amount of conditioning provided in each case when the matching conditions are satisfied. These results show that there is no fundamental obstacle to producing beam conditioning, and that the problem can be reduced to one of proper lattice design. Nevertheless, beam conditioning will not be easy to implement in practice.

  12. Evaluation of the FEL+ Program, Final Report.

    ERIC Educational Resources Information Center

    Evaluation and Training Inst., Los Angeles, CA.

    An external evaluation of the Family English Literacy, Plus (FEL+) program of the Sweetwater Union High School District (California) is presented. Program objectives included: (1) development and implementation of curriculum and activities integrating technology-assisted instruction into the existing literacy program; (2) increasing parent/child…

  13. FEL-accelerator related diagnostics

    SciTech Connect

    Kevin Jordan; David Douglas; Stephen V. Benson; Pavel Evtuschenko

    2007-08-02

    Free Electron Lasers (FEL) present a unique set of beam parameters to the diagnostics suite. The FEL requires characterization of the full six dimensional phase space of the electron beam at the wiggler and accurate alignment of the electron beam to the optical mode of the laser. In addition to the FEL requirements on the diagnostics suite, the Jefferson Lab FEL is operated as an Energy Recovered Linac (ERL) which imposes additional requirements on the diagnostics. The ERL aspect of the Jefferson Lab FEL requires that diagnostics operate over a unique dynamic range and operate with simultaneous transport of the accelerated and energy recovered beams. This talk will present how these challenges are addressed at the Jefferson Lab FEL.

  14. Tapered undulators for SASE FELs

    NASA Astrophysics Data System (ADS)

    Fawley, William M.; Huang, Zhirong; Kim, Kwang-Je; Vinokurov, Nikolai A.

    2002-05-01

    We discuss the use of tapered undulators to enhance the performance of free-electron lasers (FELs) based upon self-amplified spontaneous emission, where the radiation tends to have a relatively broad bandwidth and limited temporal coherence. Using the polychromatic FEL simulation code GINGER, we numerically demonstrate the effectiveness of tapered undulators for parameters corresponding to the Argonne low-energy undulator test line FEL and the proposed linac coherent light source.

  15. Design of a high linearity and high gain accuracy analog baseband circuit for DAB receiver

    NASA Astrophysics Data System (ADS)

    Li, Ma; Zhigong, Wang; Jian, Xu; Yiqiang, Wu; Junliang, Wang; Mi, Tian; Jianping, Chen

    2015-02-01

    An analog baseband circuit of high linearity and high gain accuracy for a digital audio broadcasting receiver is implemented in a 0.18-μm RFCMOS process. The circuit comprises a 3rd-order active-RC complex filter (CF) and a programmable gain amplifier (PGA). An automatic tuning circuit is also designed to tune the CF's pass band. Instead of the class-A fully differential operational amplifier (FDOPA) adopted in the conventional CF and PGA design, a class-AB FDOPA is specially employed in this circuit to achieve a higher linearity and gain accuracy for its large current swing capability with lower static current consumption. In the PGA circuit, a novel DC offset cancellation technique based on the MOS resistor is introduced to reduce the settling time significantly. A reformative switching network is proposed, which can eliminate the switch resistor's influence on the gain accuracy of the PGA. The measurement result shows the gain range of the circuit is 10-50 dB with a 1-dB step size, and the gain accuracy is less than ±0.3 dB. The OIP3 is 23.3 dBm at the gain of 10 dB. Simulation results show that the settling time is reduced from 100 to 1 ms. The image band rejection is about 40 dB. It only draws 4.5 mA current from a 1.8 V supply voltage.

  16. Tapered undulator for SASE FELs

    SciTech Connect

    Fawley, William M.; Huang, Zhirong; Kim, Kwang-Je; Vinokurov, Nikolai A.

    2001-09-14

    We discuss the use of tapered undulators to enhance the performance of free-electron lasers (FELs) based upon self-amplified spontaneous emission (SASE), where the radiation tends to have a relatively broad bandwidth, limited temporal phase coherence, and large amplitude fluctuations. Using the polychromatic FEL simulation code GINGER, we numerically demonstrate the effectiveness of a tapered undulator for parameters corresponding to the existing Argonne low-energy undulator test line (LEUTL) FEL. We also study possible tapering options for proposed x-ray FELs such as the Linac Coherent Light Source (LCLS).

  17. CEBAF UV/IR FEL subsystem testing and validation program

    SciTech Connect

    G.R. Neil; S.V. Benson; H.F. Dylla; H. Liu

    1995-01-01

    A design has been established for IR and UV FELs within the Laser Processing Consortium's (LPC) program for development and application of high-average-power FELs for materials processing. Hardware prototyping and testing for the IR portion of the system are underway. The driver portion has been designed based on the superconducting radio-frequency (SRF) technology now seeing large-scale application in the commissioning of CEBAF, the Continuous Electron Beam Accelerator Facility, where LPC activities are centered. As of July 1994, measurements of beam performance confirm SRF's benefits in beam quality and stability, which are applicable to high-average-power FELs.

  18. Rectangular-bore, high-gain laser plasma tube

    NASA Technical Reports Server (NTRS)

    Mollo, R. A.

    1969-01-01

    Rectangular-bore tube improves population inversion obtained from upper and terminal laser states, resulting in a significant increase in unsaturated gain factor. Radial field produces efficient pumping of upper laser state. Narrow tube dimensions cause increased diffusion flow of neon is metastable states to tube walls.

  19. Telescope considered as a very high gain antenna

    NASA Astrophysics Data System (ADS)

    Detaille, Michel; Houmault, Patrice

    1990-07-01

    A design concept for an optical-antenna telescope to be used in intersatellite communication (in the framework of the ESA SILEX project) is presented. The main technical requirements for a SILEX transmit-receive antennna telescope are reviewed, and a Cassegrain configuration based on a parabolic primary mirror, a hyperbolic secondary mirror, and a five-lense collimator (with baffles to limit stray light) is shown in diagrams and discussed in detail, with particular attention to local angular distortion and transmission-antenna gain. Results from tests on a breadboard version are presented in tables and graphs, including transmission of 92.6 percent at 820 nm, rms wavefront error less than lambda/28, optical gain 114.47 dB, backscattered energy 1.7 x 10 to the -6th at 838 nm, and stray-light intensity slightly above specification at sun aspect angles less than 4.5 deg.

  20. High gain fusion in a Staged Z-pinch

    NASA Astrophysics Data System (ADS)

    Ney, Paul; Rahman, Hafiz; Wessel, Frank; Presura, Radu

    2013-10-01

    The implosion of a Staged Z-pinch is simulated for the Sandia National Laboratories, ZR accelerator. The pinch is comprised of a silver (Ag) plasma shell, 3-mm outer radius, 0.01-cm thick, imploding onto a uniform fill (target) of deuterium-tritium (DT); the Z-R parameters are: 130 ns, 27 MA, 22 MJ; the 2-1/2 D, radiation-MHD code is MACH2. Magnetosonic shock waves generated during implosion propagate at different speeds in the liner and target, producing a shock front at the interface, and a conduction channel ahead of the liner. The interface remains stable even as the outer-surface of the liner is RT unstable. At peak compression target plasma hot spots trigger ignition with a fusion yield of 200 MJ and a net-energy gain approaching 10. The stability remains robust and the gain is unaffected for perturbations ranging from 2-5%.

  1. Harmonic cascade FEL designs for LUX

    SciTech Connect

    Penn, G.; Reinsch, M.; Wurtele, J.; Corlett, J.N.; Fawley, W.M.; Zholents, A.; Wan, W.

    2004-07-16

    LUX is a design concept for an ultrafast X-ray science facility, based on an electron beam accelerated to GeV energies in are circulating linac. Included in the design are short duration (200 fs or shorter FWHM) light sources using multiple stages of higher harmonic generation, seeded by a 200-250 nm laser of similar duration. This laser modulates the energy of a group of electrons within the electron bunch; this section of the electron bunch then produces radiation at a higher harmonic after entering a second, differently tuned undulator. Repeated stages in a cascade yield increasing photon energies up to 1 keV. Most of the undulators in the cascade operate in the low-gain FEL regime. Harmonic cascades have been designed for each pass of the recirculating linac up to a final electron beam energy of 3.1 GeV. For a given cascade, the photon energy can be selected over a wide range by varying the seed laser frequency and the field strength in the undulators. We present simulation results using the codes GENESIS and GINGER, as well as the results of analytical models which predict FEL performance. We discuss lattice considerations pertinent for harmonic cascade FELs, as well as sensitivity studies and requirements on the electron beam.

  2. FEL Trajectory Analysis for the VISA Experiment

    SciTech Connect

    Nuhn, Heinz-Dieter

    1998-10-06

    The Visual to Infrared SASE Amplifier (VISA) [1] FEL is designed to achieve saturation at radiation wavelengths between 800 and 600 nm with a 4-m pure permanent magnet undulator. The undulator comprises four 99-cm segments each of which has four FODO focusing cells superposed on the beam by means of permanent magnets in the gap alongside the beam. Each segment will also have two beam position monitors and two sets of x-y dipole correctors. The trajectory walk-off in each segment will be reduced to a value smaller than the rms beam radius by means of magnet sorting, precise fabrication, and post-fabrication shimming and trim magnets. However, this leaves possible inter-segment alignment errors. A trajectory analysis code has been used in combination with the FRED3D [2] FEL code to simulate the effect of the shimming procedure and segment alignment errors on the electron beam trajectory and to determine the sensitivity of the FEL gain process to trajectory errors. The paper describes the technique used to establish tolerances for the segment alignment.

  3. High current operation of a storage-ring free-electron laser

    NASA Astrophysics Data System (ADS)

    Roux, R.; Couprie, M. E.; Bakker, R. J.; Garzella, D.; Nutarelli, D.; Nahon, L.; Billardon, M.

    1998-11-01

    The operation of storage-ring free-electron lasers (SRFEL) at high current still represents a challenge because of the growth of longitudinal beam instabilities. One of these, the quadrupolar coherent synchrotron oscillation, is very harmful for free-electron-laser (FEL) operation. On the Super-ACO storage ring, they either prevent the FEL start-up, or result in a very poor stability of the FEL source. A new feedback system to damp the quadrupolar coherent synchrotron oscillation has been installed on the ring and the stabilized beam parameters have been systematically measured. As a result, the FEL gain is higher and the FEL operates more easily and with a higher average power. Its stability, which is very critical for user applications, has been significantly improved as it has been observed via systematic measurements of FEL dynamics performed with a double sweep streak camera.

  4. Short wavelength FELS

    SciTech Connect

    Sheffield, R.L.

    1991-01-01

    The generation of coherent ultraviolet and shorter wavelength light is presently limited to synchrotron sources. The recent progress in the development of brighter electron beams enables the use of much lower energy electron rf linacs to reach short-wavelengths than previously considered possible. This paper will summarize the present results obtained with synchrotron sources, review proposed short- wavelength FEL designs and then present a new design which is capable of over an order of magnitude higher power to the extreme ultraviolet. 17 refs., 10 figs.

  5. Numerical simulations of x-ray generation in miltisectional FELs

    SciTech Connect

    Pitatelev, M.M.

    1995-12-31

    The process of x-ray generation in milticomponent FELs with alternate undulator and dispersion sections is investigate. The coptuter simulation was fulfilled for the ultrarelativistic electron beams. It was shown that the use of much number of dispersion sections allows to increase the gain considerably and to use more short magnetic systems.

  6. Self-consistent quantum-electrodynamic calculation of spontaneous emission and small-signal gain in high-voltage free-electron lasers

    NASA Astrophysics Data System (ADS)

    Chang, C. S.; Fluhler, H. U.

    1990-10-01

    A self-consistent QED (SCQED) theory of spontaneous emission of radiation and single-photon small-signal gain (SSG) is developed for FELs using the Weisskopf-Wigner method. The results agree with existing experimental data on both the line broadening and the line shift and to a reasonable extent with the measured gain. It is shown that the spontaneous-emission spectrum obtained from classical or conventional FEL theories is valid only in the limit of a short undulator that contains a small number of periods. The SSG derived from the SCQED theory is shown to reduce to Colson's (1977) gain formula in the classical limit. However, the SCQED theory predicts significant reductions in the SSG that agree well with the ACO gain data and are not predicted well by Colson's formula. It is discovered that a fundamental physical gain limit exists that is universal to all types of FELs within the limits of the single-photon transition scheme considered.

  7. Software reconfigurable highly flexible gain switched optical frequency comb source.

    PubMed

    Pascual, M Deseada Gutierrez; Zhou, Rui; Smyth, Frank; Anandarajah, Prince M; Barry, Liam P

    2015-09-01

    The authors present the performance and noise properties of a software reconfigurable, FSR and wavelength tunable gain switched optical frequency comb source. This source, based on the external injection of a temperature tuned Fabry-Pérot laser diode, offers quasi-continuous wavelength tunability over the C-band (30nm) and FSR tunability ranging from 6 to 14GHz. The results achieved demonstrate the excellent spectral quality of the comb tones (RIN ~-130dB/Hz and low phase noise of 300kHz) and its outstanding stability (with fluctuations of the individual comb tones of less than 0.5dB in power and 5pm in wavelength, characterized over 24hours) highlighting its suitability for employment in next generation flexible optical transmission networks. PMID:26368425

  8. NUTRIENT REQUIREMENTS OF HIGH-LEAN GAIN SWINE AT A HIGH ENVIRONMENTAL TEMPERATURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High-lean gain swine initially averaging 85 kg were assigned to 96 individual pens and given one of six diets ranging in the ratio of Total Ileal Digestible (TID) Lysine:Metabolizable Energy (ME) of 1.23 to 2.28 g/MCal. Pigs and feed intake were weighed weekly and backfat was measured on two week i...

  9. High gain ytterbium doped Ge pedestal large pitch fiber

    NASA Astrophysics Data System (ADS)

    Gaida, Christian; Stutzki, Fabian; Jansen, Florian; Otto, Hans-Jürgen; Eidam, Tino; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2014-03-01

    Large mode area rod-type fibers have enabled amplification of ultra-short pulses to mJ pulse energy and MW peak powers. For very large mode field areas, fibers have to be designed as rigid rods with typical fiber lengths of around 1 m for efficient operation. A shorter fiber length can be desirable to reduce the packaging size of commercial systems and to decrease the impact of parasitic nonlinear effects for peakpower scaling. The fiber design presented here is based on a modified large-pitch fiber with an effectively higher ytterbium concentration in the fiber core. To achieve index matching the cladding index needs to be changed. In this contribution we propose to co-dope the passive host material with germanium to match both indices and to obtain a higher Yb-concentration within the active core. Compared to standard LPF, where the core index is reduced by co-doping the core with Flourine, the ytterbium doping concentration of this novel germanium-pedestal LPF is doubled. A detailed numerical and experimental investigation shows that with short fiber lengths <40cm is feasible to achieve output powers beyond 100W with 10W seed. Significantly higher gains, of nearly 30 dB, can be achieved for fiber lengths in the order of 60cm. A similar gain can be expected in a conventional LPF with 1.20 m length. In conclusion, we demonstrate a fiber design for significantly enhanced energy storage per fiber length and improved pump absorption. This concept will notably reduce the footprint of ultra-short fiber laser systems.

  10. Simulation of a regenerative MW FEL amplifier

    SciTech Connect

    Nguyen, R.T.; Colson, W.B.; Wong, R.K.; Sheffield, R.L.

    1997-08-01

    Both oscillator and regenerative amplifier configurations are being studied to optimize the design of a MW class FEL. The regenerative amplifier uses a longer undulator and relies on higher extraction efficiency to achieve high average power, whereas the oscillator is a more compact overall design requiring the transport of the high energy electron beam around bends for energy recovery. Using parameters extrapolated from the 1 kW LANL regenerative amplifier, simulations study the feasibility of achieving 1 MW average power.

  11. Quasi-isochronous storage ring for enhanced FEL performance

    SciTech Connect

    Ohgaki, H.; Robin, D.; Yamazaki, Y.

    1995-08-01

    A compact storage ring is designed to be used as a driver for an FEL. This ring can be operated very close to zero momentum compaction factor ({alpha}) to increase the electron density and thus the gain of the FEL. In order to control {alpha} with zero dispersion in the straight sections the authors use an inverted dipole located between the bending magnets and 4-families of quadrupoles. By using 3-families of sextupoles they can control the 2 transverse chromaticities and 2nd order momentum compaction. They find that the ring has sufficient dynamic aperture for good performance.

  12. The Stanford Picosecond FEL Center

    SciTech Connect

    Schwettman, H.A.; Smith, T.I.; Swent, R.L.

    1995-12-31

    In the past two years, FELs have decisively passed the threshold of scientific productivity. There are now six FEL facilities in the United States and Europe, each delivering more than 2000 hours of FEL beam time per year. at the present time approximately 100 papers are published each in referred journals describing optics experiments performed with FELs. Despite the recent success there are important challenges the FEL facilities must address. At Stanford these challenges include: (1) Providing sufficient experimental time at reasonable cost: At Stanford we provide 2000 hours of experimental time per year at a cost of approximately $500 per hour: We are now studying options for markedly increasing experimental time and decreasing cost per hour. (2) Competing effectively with conventional lasers in the mid-IR: Despite the NRC report we do not intend to concede the mid-IR to conventional lasers. FELs are capable of providing optical beams of exceptional quality and stability, and they can also be remarkable flexible devices. Improvements in our superconducting linac driver and our optical beam conditioning systems will dramatically enhance our FEL experimental capabilities. (3) making the transition from first generation to second generation experiments: Important pump-probe and photon echo experiments have been performed at Stanford and others are feasible using present capabilities. None-the-less we are now investing substantial experimental time to improving signal-to-noise and developing other optical cababilities. (4) Extending operation to the far-infrared where the FEL is unique inits capabilities: {open_quotes}FIREFLY{close_quotes} will extend our FEL capabilities to 100 microns. We are now seeking funds for optical instrumentation. (5) Creating and maintaining a good environment for graduate students.

  13. Dielectric Wakefield Accelerator to drive the future FEL Light Source.

    SciTech Connect

    Jing, C.; Power, J.; Zholents, A. )

    2011-04-20

    X-ray free-electron lasers (FELs) are expensive instruments and a large part of the cost of the entire facility is driven by the accelerator. Using a high-energy gain dielectric wake-field accelerator (DWA) instead of the conventional accelerator may provide a significant cost saving and reduction of the facility size. In this article, we investigate using a collinear dielectric wakefield accelerator to provide a high repetition rate, high current, high energy beam to drive a future FEL x-ray light source. As an initial case study, a {approx}100 MV/m loaded gradient, 850 GHz quartz dielectric based 2-stage, wakefield accelerator is proposed to generate a main electron beam of 8 GeV, 50 pC/bunch, {approx}1.2 kA of peak current, 10 x 10 kHz (10 beamlines) in just 100 meters with the fill factor and beam loading considered. This scheme provides 10 parallel main beams with one 100 kHz drive beam. A drive-to-main beam efficiency {approx}38.5% can be achieved with an advanced transformer ratio enhancement technique. rf power dissipation in the structure is only 5 W/cm{sup 2} in the high repetition rate, high gradient operation mode, which is in the range of advanced water cooling capability. Details of study presented in the article include the overall layout, the transform ratio enhancement scheme used to increase the drive to main beam efficiency, main wakefield linac design, cooling of the structure, etc.

  14. Second harmonic FEL oscillation

    NASA Astrophysics Data System (ADS)

    Neil, George R.; Benson, S. V.; Biallas, G.; Freund, H. P.; Gubeli, J.; Jordan, K.; Myers, S.; Shinn, M. D.

    2002-05-01

    We have produced and measured for the first time second harmonic oscillation in the infrared region by the high-average-power Jefferson Lab Infrared Free Electron Laser. The finite geometry and beam emittance allows sufficient gain for lasing to occur. We were able to lase at pulse rates up to 74.85 MHz and could produce over 4.5 W average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM 01 mode. We present results of initial source performance measurements and comparisons with theory and simulation.

  15. Large-Scale High-Resolution Simulations of High Gain Direct-Drive ICF targets

    NASA Astrophysics Data System (ADS)

    Schmitt, Andrew J.

    2003-10-01

    High gain directly-driven targets have been designed using new concepts that mitigate the Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities. Two-dimensional simulations of pellets using these techniques (e.g., "picket" laser pulses) show that high (>100) gain can survive in the face of the hydro instabilities seeded by laser and pellet imperfections. These new designs appear to be substantially more robust than earlier designs. We are using the highly-parallelized sliding-zone Eulerian FAST radiation hydrocode to study yield degradation in these designs. The special challenge in performing these simulations for direct-drive laser ICF is that both high resolution and large dynamic range are needed. High resolution of the whole target is needed to represent all of the scales important during the implosion. A large dynamic range is required to resolve the initially tiny surface and imprint perturbations that grow exponentially during acceleration. We find that the rapid growth of the shell perturbations during the acceleration phase is in good agreement with simple RT modeling before significant nonlinearity occurs. However, the Richtmyer-Meshkov growth during the early pellet compression phase poses a challenge particularly for multimode simulations because of the extremely small initial amplitude for each mode. We will present the results from large-scale pellet implosion simulations, and discuss the challenges and progress achieved in the numerical modeling of these high gain designs.

  16. ASE suppression in high-gain solid-state amplifiers by a leak method

    NASA Astrophysics Data System (ADS)

    Zhang, Yongliang; Ye, Haixian; Li, Mingzhong; Zheng, Jiangang; Wei, Xiaofeng; Gao, Song; Deng, Qinghua; Jiang, Xinying; Yan, Xiongwei; Wang, Zhenguo

    2013-07-01

    A leak method was developed to suppress amplified spontaneous emission (ASE) in large-aperture high-gain solid-state amplifiers. The gain medium edges are processed into an arris. The ASE ray will undergo reflection several times at the arris surface when it propagates to the gain medium edges, and most of its power will leak out. This leak method was tested in an experiment, in which a piece of commonly used gain medium was processed for contrast. The maximal increase of the gain value was 5.26% with the maximal pump power.

  17. An S-band high gain relativistic klystron amplifier with high phase stability

    SciTech Connect

    Wu, Y.; Li, Z. H.; Xu, Z.; Ma, Q. S.; Xie, H. Q.

    2014-11-15

    For the purpose of coherent high power microwave combining, an S-band high gain relativistic klystron amplifier with high phase stability is presented and studied. By the aid of 3D particle-in-cell code and circuit simulation software, the mechanism of parasitic oscillation in the device is investigated. And the RF lossy material is adopted in the simulation and experiment to suppress the oscillation. The experimental results show that with an input RF power of 10 kW, a microwave pulse with power of 1.8 GW is generated with a gain of 52.6 dB. And the relative phase difference fluctuation between output microwave and input RF signal is less than ±10° in 90 ns.

  18. The SwissFEL Experimental Laser facility.

    PubMed

    Erny, Christian; Hauri, Christoph Peter

    2016-09-01

    The hard X-ray laser SwissFEL at the Paul Scherrer Institute is currently being commissioned and will soon become available for users. In the current article the laser facility is presented, an integral part of the user facility, as most time-resolved experiments will require a versatile optical laser infrastructure and precise information about the relative delay between the X-ray and optical pulse. The important key parameters are a high availability and long-term stability while providing advanced laser performance in the wavelength range from ultraviolet to terahertz. The concept of integrating a Ti:sapphire laser amplifier system with subsequent frequency conversion stages and drift compensation into the SwissFEL facility environment for successful 24 h/7 d user operation is described. PMID:27577769

  19. High gain durable anti-reflective coating with oblate voids

    DOEpatents

    Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze'ev

    2016-06-28

    Disclosed herein are single layer transparent coatings with an anti-reflective property, a hydrophobic property, and that are highly abrasion resistant. The single layer transparent coatings contain a plurality of oblate voids. At least 1% of the oblate voids are open to a surface of the single layer transparent coatings.

  20. High-gain, high-bandwidth, rail-to-rail, constant-gm CMOS operational amplifier

    NASA Astrophysics Data System (ADS)

    Huang, Hong-Yi; Wang, Bo-Ruei

    2013-01-01

    This study presents a high-gain, high-bandwidth, constant-gm , rail-to-rail operational amplifier (op-amp). The constant transconductance is improved with a source-to-bulk bias control of an input pair. A source degeneration scheme is also adapted to the output stage for receiving wide input range without degradation of the gain. Additionally, several compensation schemes are employed to enhance the stability. A test chip is fabricated in a 0.18 µm complementary metal-oxide semiconductor process. The active area of the op-amp is 181 × 173 µm2 and it consumes a power of 2.41 mW at a supply voltage of 1.8 V. The op-amp achieves a dc gain of 94.3 dB and a bandwidth of 45 MHz when the output capacitive load is connected to an effective load of 42.5 pF. A class-AB output stage combining a slew rate (SR) boost circuit provides a sinking current of 6 mA and an SR of 17 V/µs.

  1. High gain photoconductive semiconductor switch having tailored doping profile zones

    SciTech Connect

    Baca, Albert G.; Loubriel, Guillermo M.; Mar, Alan; Zutavern, Fred J; Hjalmarson, Harold P.; Allerman, Andrew A.; Zipperian, Thomas E.; O'Malley, Martin W.; Helgeson, Wesley D.; Denison, Gary J.; Brown, Darwin J.; Sullivan, Charles T.; Hou, Hong Q.

    2001-01-01

    A photoconductive semiconductor switch with tailored doping profile zones beneath and extending laterally from the electrical contacts to the device. The zones are of sufficient depth and lateral extent to isolate the contacts from damage caused by the high current filaments that are created in the device when it is turned on. The zones may be formed by etching depressions into the substrate, then conducting epitaxial regrowth in the depressions with material of the desired doping profile. They may be formed by surface epitaxy. They may also be formed by deep diffusion processes. The zones act to reduce the energy density at the contacts by suppressing collective impact ionization and formation of filaments near the contact and by reducing current intensity at the contact through enhanced current spreading within the zones.

  2. The universal method for optimization of undulator tapering in FEL amplifiers

    NASA Astrophysics Data System (ADS)

    Schneidmiller, E. A.; Yurkov, M. V.

    2015-05-01

    Technique of undulator tapering in the post-saturation regime is used at the existing x-ray FELs for increasing the radiation power. There are also discussions on the future of high peak and average power FELs for scientific and industrial applications. Diffraction effects essentially influence on the choice of the tapering strategy. Recent studies resulted in an general law of the undulator tapering for a seeded FEL amplifier. In this paper we extend these results for the case of the Self Amplified Spontaneous Emission (SASE) FEL.

  3. FEL for the polymer processing industries

    NASA Astrophysics Data System (ADS)

    Kelley, Michael J.

    1997-05-01

    Polymers are everywhere in modern life because of their unique combination of end-use functionalities, ease of processing, recycling potential and modest cost. The physical and economic scope of the infrastructure committed to present polymers makes the introduction of entirely new chemistry unlikely. Rather, the breadth of commercial offerings more likely to shrink in the face of the widening mandate for recycling, especially of packaging. Improved performance and new functionality must therefore come by routes such as surface modification. However they must come with little environmental impact and at painfully low cost. Processing with strongly absorbed light offers unique advantages. The journal and patent literatures disclose a number of examples of benefits that can be achieved, principally by use of excimer lasers or special UV lamps. Examples of commercialization are few, however, because of the unit cost and maximum scale of existing light sources. A FEL, however, offers unique advantages: tunability to the optimum wavelength, potential for scale up to high average power, and a path to attractively low unit cost of light. A business analysis of prospective applications defines the technical and economic requirements a FEL for polymer surface processing must meet. These are compared to FEL technology as it now stands and as it is envisioned.

  4. Staged energy cascades for the LUX FEL

    SciTech Connect

    Penn, G.

    2004-07-27

    Designs and simulation studies for harmonic cascades, consisting of multiple stages of harmonic generation in free electron lasers (FELs), are presented as part of the LUX R&D project to design ultrafast, high photon energy light sources for basic science. Beam energies of 1.1, 2.1, and 3.1 GeV, corresponding to each pass through a recirculating linac, have independent designs for the harmonic cascade. Simulations were performed using the GENESIS FEL code, to obtain predictions for the performance of these cascades over a wide range of photon energies in terms of the peak power and laser profile. The output laser beam consists of photon energies of up to 1 keV, with durations of the order of 200 fs or shorter. The contribution of shot noise to the laser output is minimal, however fluctuations in the laser and electron beam properties can lead to variations in the FEL output. The sensitivity of the cascade to electron beam properties and misalignments is studied, taking advantage of the fact that GENESIS is a fully 3-dimensional code.

  5. In-circuit-measurement of parasitic elements in high gain high bandwidth low noise transimpedance amplifiers.

    PubMed

    Cochems, P; Kirk, A; Zimmermann, S

    2014-12-01

    Parasitic elements play an important role in the development of every high performance circuit. In the case of high gain, high bandwidth transimpedance amplifiers, the most important parasitic elements are parasitic capacitances at the input and in the feedback path, which significantly influence the stability, the frequency response, and the noise of the amplifier. As these parasitic capacitances range from a few picofarads down to only a few femtofarads, it is nearly impossible to measure them accurately using traditional LCR meters. Unfortunately, they also cannot be easily determined from the transfer function of the transimpedance amplifier, as it contains several overlapping effects and its measurement is only possible when the circuit is already stable. Therefore, we developed an in-circuit measurement method utilizing minimal modifications to the input stage in order to measure its parasitic capacitances directly and with unconditional stability. Furthermore, using the data acquired with this measurement technique, we both proposed a model for the complicated frequency response of high value thick film resistors as they are used in high gain transimpedance amplifiers and optimized our transimpedance amplifier design. PMID:25554310

  6. Long lifetime, high density single-crystal erbium compound nanowires as a high optical gain material

    NASA Astrophysics Data System (ADS)

    Yin, Leijun; Ning, Hao; Turkdogan, Sunay; Liu, Zhicheng; Nichols, Patricia L.; Ning, C. Z.

    2012-06-01

    Erbium-containing materials of long lifetime and high Er density are important for achieving strong luminescence and high optical gain in compact integrated photonics devices. We have systematically studied the lifetime and crystal quality as a function of growth conditions for an erbium compound that we recently reported, erbium chloride silicate (ECS). The lifetime for the best quality ECS nanowires can be as long as 540 μs, the longest for high-density Er-materials, representing a lifetime-density product as high as 8.7 × 1018 s cm-3. Such high density, long lifetime erbium materials can find many interesting applications such as compact lasers or amplifiers.

  7. Hypoallergenic derivatives of Fel d 1 obtained by rational reassembly for allergy vaccination and tolerance induction

    PubMed Central

    Curin, M.; Weber, M.; Thalhamer, T.; Swoboda, I.; Focke-Tejkl, M.; Blatt, K.; Valent, P.; Marth, K.; Garmatiuk, T.; Grönlund, H.; Thalhamer, J.; Spitzauer, S.; Valenta, R.

    2015-01-01

    Summary Background and objective The major cat allergen Fel d 1 represents one of the most important respiratory allergens. Aim of this study was to engineer recombinant Fel d 1 derivatives with reduced IgE reactivity and preserved T cell epitopes for vaccination and tolerance induction. Methods Seven recombinant mosaic proteins were generated by reassembly of non-IgE-reactive peptides of Fel d 1 which contained the sequence elements for induction of allergen-specific blocking IgG antibodies and T cell epitopes. Mosaic proteins were expressed in Escherichia coli using codon-optimized synthetic genes and compared with Fel d 1 regarding structural fold by circular dichroism, IgE-binding capacity, activation of allergic patients’ basophils and ability to induce allergen-specific blocking IgG antibodies upon immunization. Results Although each of the mosaic proteins had lost the alpha-helical fold typical for Fel d 1, a strong reduction in IgE reactivity as well as allergenic activity in basophil activation assays was only obtained for three constructs, two reassembled fragments (Fel d 1 MB, Fel d 1 MC) and a fusion of the latter two (Fel d 1 MF) in which the cysteines of Fel d 1 MC were replaced by serines. Immunization of rabbits with Fel d 1 MB, MC and MF induced high levels of IgG antibodies that inhibited IgE reactivity of cat-allergic patients to Fel d 1 in a comparable manner as IgG induced with the wild-type allergen. Conclusions We report the development of hypoallergenic reassembled Fel d 1 proteins suitable for vaccination and tolerance induction in cat-allergic patients. PMID:24552249

  8. A 1 to 18 GHz high gain ultra-broadband amplifier with temperature compensation

    NASA Astrophysics Data System (ADS)

    Ariel, D.; Thibout, T.; Lacombe, J. L.

    1989-05-01

    Design and performance of a high gain ultra-broadband hybrid amplifier with temperature compensation are presented. The amplifier consists of six distributed amplifier stages using GaAs FETs. Design emphasis was on minimizing gain variations with temperature; this was achieved by biasing the gates of the FETs with a temperature varying voltage. The amplifier exhibits a gain of 35 dB with a maximum deviation of + or - 4 dB over the frequency range from 1 to 18 GHz and the temperature range from -55 to +85 C. The gain flatness and temperature stability performance of this amplifier make it useful for EW subsystem applications.

  9. Design, development and testing of the x-ray timing explorer High Gain Antenna System

    NASA Technical Reports Server (NTRS)

    Lecha, Javier; Woods, Claudia; Phan, Minh

    1995-01-01

    The High Gain Antenna System (HGAS), consisting of two High Gain Antenna Deployment Systems (HGADS) and two Antenna Pointing Systems (APS), is used to position two High Gain Antennas (HGA) on the X-Ray Timing Explorer (XTE). A similar APS will be used on the upcoming Tropical Rainfall Measuring Mission (TRMM). Both XTE and TRMM are NASA in-house satellites. The salient features of the system include the two-axis gimbal and control electronics of the APS and the spring deployment and latch/release mechanisms of the HGADS. This paper describes some of the challenges faced in the design and testing of this system and their resolutions.

  10. High Gain Antenna Gimbal for the 2003-2004 Mars Exploration Rover Program

    NASA Technical Reports Server (NTRS)

    Sokol, Jeff; Krishnan, Satish; Ayari, Laoucet

    2004-01-01

    The High Gain Antenna Assemblies built for the 2003-2004 Mars Exploration Rover (MER) missions provide the primary communication link for the Rovers once they arrive on Mars. The High Gain Antenna Gimbal (HGAG) portion of the assembly is a two-axis gimbal that provides the structural support, pointing, and tracking for the High Gain Antenna (HGA). The MER mission requirements provided some unique design challenges for the HGAG. This paper describes all the major subsystems of the HGAG that were developed to meet these challenges, and the requirements that drove their design.

  11. Coherent harmonic production using a two-section undulator FEL

    SciTech Connect

    Jaroszynski, D.A.; Prazeres, R.; Glotin, F.

    1995-12-31

    We present measurements and a theoretical analysis of a new method of generating harmonic radiation in a free-electron laser oscillator with a two section undulator in a single optical cavity. To produce coherent harmonic radiation the undulator is arranged so that the downstream undulator section resonance frequency matches a harmonic of the upstream undulator. Both the fundamental and the harmonic optical fields evolve in the same optical cavity and are coupled out with different extraction fractions using a hole in one of the cavity mirrors. We present measurements that show that the optical power at the second and third harmonic can be enhanced by more than an order of magnitude in this fundamental/harmonic configuration. We compare the production of harmonic radiation of a two sectioned fundamental/harmonic undulator with that produced from a FEL operating at its highest efficiency with a step-tapered undulator, where the bunching at the end of the first section is very large. We examine, the dependence of the harmonic power on the intracavity power by adjusting the optical cavity desynchronism, {delta}L. We also examine the evolution of the fundamental and harmonic powers as a function of cavity roundtrip number to evaluate the importance of the small signal gain at the harmonic. We compare our measurements with predictions of a multi-electron numerical model that follows the evolution of fundamental and harmonic power to saturation. This fundamental/harmonic mode, of operation of the FEL may have useful applications in the production of coherent X-ray and VUV radiation, a spectral range where high reflectivity optical cavity mirrors are difficult or impossible to manufacture.

  12. Low-noise pseudomorphic dual-gate cascode HEMT's with extremely high gain

    NASA Astrophysics Data System (ADS)

    Wenger, J.; Narozny, P.; Daembkes, H.; Splettstoesser, J.; Werres, C.

    1992-02-01

    Quarter-micron InGaAs-GaAs dual-gate HEMTs connected as a cascode MMIC in a compact manner have been fabricated and investigated. The devices show a high output impedance and a very low feedback capacitance, resulting in a high-voltage gain factor gm/gd of 125 and a Cgs/Cgd ratio of 45. The current gain cutoff frequency fT is 45 GHz and the maximum stable gain is 23.5 dB at 10 GHz and 19 dB at 20 GHz. The pseudomorphic cascode HEMTs show a low-noise figure of 1.1 dB with an associated gain of 22 dB at 10 GHz, at 18 GHz the minimum noise figure is 1.9 dB with 16-dB gain.

  13. To kill a kangaroo: understanding the decision to pursue high-risk/high-gain resources

    PubMed Central

    Jones, James Holland; Bird, Rebecca Bliege; Bird, Douglas W.

    2013-01-01

    In this paper, we attempt to understand hunter–gatherer foraging decisions about prey that vary in both the mean and variance of energy return using an expected utility framework. We show that for skewed distributions of energetic returns, the standard linear variance discounting (LVD) model for risk-sensitive foraging can produce quite misleading results. In addition to creating difficulties for the LVD model, the skewed distributions characteristic of hunting returns create challenges for estimating probability distribution functions required for expected utility. We present a solution using a two-component finite mixture model for foraging returns. We then use detailed foraging returns data based on focal follows of individual hunters in Western Australia hunting for high-risk/high-gain (hill kangaroo) and relatively low-risk/low-gain (sand monitor) prey. Using probability densities for the two resources estimated from the mixture models, combined with theoretically sensible utility curves characterized by diminishing marginal utility for the highest returns, we find that the expected utility of the sand monitors greatly exceeds that of kangaroos despite the fact that the mean energy return for kangaroos is nearly twice as large as that for sand monitors. We conclude that the decision to hunt hill kangaroos does not arise simply as part of an energetic utility-maximization strategy and that additional social, political or symbolic benefits must accrue to hunters of this highly variable prey. PMID:23884091

  14. To kill a kangaroo: understanding the decision to pursue high-risk/high-gain resources.

    PubMed

    Jones, James Holland; Bird, Rebecca Bliege; Bird, Douglas W

    2013-09-22

    In this paper, we attempt to understand hunter-gatherer foraging decisions about prey that vary in both the mean and variance of energy return using an expected utility framework. We show that for skewed distributions of energetic returns, the standard linear variance discounting (LVD) model for risk-sensitive foraging can produce quite misleading results. In addition to creating difficulties for the LVD model, the skewed distributions characteristic of hunting returns create challenges for estimating probability distribution functions required for expected utility. We present a solution using a two-component finite mixture model for foraging returns. We then use detailed foraging returns data based on focal follows of individual hunters in Western Australia hunting for high-risk/high-gain (hill kangaroo) and relatively low-risk/low-gain (sand monitor) prey. Using probability densities for the two resources estimated from the mixture models, combined with theoretically sensible utility curves characterized by diminishing marginal utility for the highest returns, we find that the expected utility of the sand monitors greatly exceeds that of kangaroos despite the fact that the mean energy return for kangaroos is nearly twice as large as that for sand monitors. We conclude that the decision to hunt hill kangaroos does not arise simply as part of an energetic utility-maximization strategy and that additional social, political or symbolic benefits must accrue to hunters of this highly variable prey. PMID:23884091

  15. Simultaneous Equations Models of the Educational Process for High and Low Achievers. Fels Center of Government Discussion Paper No. 89.

    ERIC Educational Resources Information Center

    Boardman, Anthony E.; Phillips, Barbara R.

    Separate simultaneous equations models for the educational process for high and low achievers are estimated with two stage least squares for a sample of the 12th grade Coleman data. The nine observed endogenous variables concern cognitive, non-cognitive, and attitudinal factors. The 48 exogenous variables concern demographic, home, peer, teacher,…

  16. Brightness and coherence of synchrotron radiation and high-gain free electron lasers

    SciTech Connect

    Kim, K.J.

    1986-10-01

    The characteristics of synchrotron radiation are reviewed with particular attention to its phase-space properties and coherence. The transition of the simple undulator radiation to more intense, more coherent high-gain free electron lasers, is discussed.

  17. Electron beam effects in a UV FEL

    SciTech Connect

    Wong, R.K.; Blau, J.; Colson, W.B.

    1995-12-31

    At the Continuous Electron Beam Accelerator Facility (CEBAF), a free electron laser (FEL) is designed to produce ultraviolet (UV) light. A four-dimensional FEL simulation studies the effects of betatron oscillations, external focusing, and longitudinal pulse compression of the electron beam on the FEL performance.

  18. Gain media edge treatment to suppress amplified spontaneous emission in a high power laser

    DOEpatents

    Hackel, Lloyd A.; Soules, Thomas F.; Fochs, Scott N.; Rotter, Mark D.; Letts, Stephan A.

    2008-12-09

    A novel method and apparatus for suppressing ASE and parasitic oscillation modes in a high average power laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges using a substantially high index bonding elastomer or epoxy to a predetermined electromagnetic absorbing arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE and parasitic oscillation modes can be effectively suppressed.

  19. High-Gain AlxGa1-xAs/GaAs Transistors For Neural Networks

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Hoon; Lin, Steven H.

    1991-01-01

    High-gain AlxGa1-xAs/GaAs npn double heterojunction bipolar transistors developed for use as phototransistors in optoelectronic integrated circuits, especially in artificial neural networks. Transistors perform both photodetection and saturating-amplification functions of neurons. Good candidates for such application because structurally compatible with laser diodes and light-emitting diodes, detect light, and provide high current gain needed to compensate for losses in holographic optical elements.

  20. Seeded quantum FEL at 478 keV

    SciTech Connect

    Guenther, M. M.; Jentschel, M.; Thirolf, P. G.; Seggebrock, T.; Habs, D.

    2012-07-09

    We present for the first time the concept of a seeded {gamma} quantum Free-Electron-Laser (QFEL) at 478 keV, which has very different properties compared to a classical. The basic concept is to produce a highly brilliant {gamma} beam via SASE. To produce highly intense and coherent {gamma} beam, we intend to use a seeded FEL scheme. Important for the production of such a {gamma} beam are novel refractive {gamma}-lenses for focusing and an efficient monochromator, allowing to generate a very intense and coherent seed beam. The energy of the {gamma} beam is 478 keV, corresponding to a wavelength in the sub-Angstrom regime (1/38 A). To realize a coherent {gamma} beam at 478 keV, it is necessary to use a quantum FEL design. At such high radiation energies a classical description of the {gamma}-FEL becomes wrong.

  1. Application of FEL technique for constructing high-intensity, monochromatic, polarized gamma-sources at storage rings

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Ulyanov, Yu.N.

    1995-12-31

    A possibility to construct high-intensity tunable monochromatic{gamma}-source at high energy storage rings is discussed. It is proposed to produce {gamma}-quanta by means of Compton backscattering of laser photons on electrons circulating in the storage. The laser light wavelength is chosen in such a way that after the scattering, the electron does not leave the separatrix. So as the probability of the scattering is rather small, energy oscillations are damped prior the next scattering. As a result, the proposed source can operate in {open_quotes}parasitic{close_quote} mode not interfering with the main mode of the storage ring operation. Analysis of parameters of existent storage rings (PETRA, ESRF, Spring-8, etc) shows that the laser light wavelength should be in infrared, {lambda}{approximately} 10 - 400 {mu}m, wavelength band. Installation at storage rings of tunable free-electron lasers with the peak and average output power {approximately} 10 MW and {approximately} 1 kW, respectively, will result in the intensity of the {gamma}-source up to {approximately} 10{sup 14}s{sup -1} with tunable {gamma}-quanta energy from several MeV up to several hundreds MeV. Such a {gamma}-source will reveal unique possibilities for precision investigations in nuclear physics.

  2. On use of time-dependent microwave fields to increase an FEL oscillator efficiency

    SciTech Connect

    Saldin, E.L.; Schneidmiller, E.A.; Yurkov, M.V.

    1995-12-31

    Various schemes of a high efficiency FEL oscillator with time-dependent accelerating (or decelerating) microwave field in interaction region are proposed. All the, schemes are based on standard accelerating structure and undulator technology. Feasibility of the proposed schemes is confirmed by results of numerical simulations. Realistic examples of FEL oscillators of infrared and visible wavelength ranges with efficiency about 20 % are presented.

  3. Transverse Gradient Undulators and FEL operating with large energy spread

    NASA Astrophysics Data System (ADS)

    Ciocci, F.; Dattoli, G.; Sabia, E.

    2015-12-01

    Undulators exhibiting a gradient of the field in the transverse direction have been proposed to mitigate the effects of the gain dilution in Free Electron Laser devices operating with large energy spread. The actual use of the device depends on the realization of a field distribution with quasi-vanishing quadrupolar terms in the tapering directions. We analyze the effect of a Transverse Gradient Undulator on the FEL operation and critically review the possibility of an appropriate field implementation.

  4. Evolution of longitudinal modes in low voltage FEL

    SciTech Connect

    Stuart, R.A.; Al-Shamma`a, A.; Shaw, A.

    1995-12-31

    A low voltage FEL operating at 130 kV which can be run cw with a continuous electron beam current level up to 12 mA has been constructed for the X-Band microwave range (8-12 GHz). In this poster, we will report on the dependence on time, after the electron beam is switched on, of the growth and competition of those longitudinal modes in the cavity having nett gain.

  5. Loop gain stabilizing with an all-digital automatic-gain-control method for high-precision fiber-optic gyroscope.

    PubMed

    Zheng, Yue; Zhang, Chunxi; Li, Lijing; Song, Lailiang; Chen, Wen

    2016-06-10

    For a fiber-optic gyroscope (FOG) using electronic dithers to suppress the dead zone, without a fixed loop gain, the deterministic compensation for the dither signals in the control loop of the FOG cannot remain accurate, resulting in the dither residuals in the FOG rotation rate output and the navigation errors in the inertial navigation system. An all-digital automatic-gain-control method for stabilizing the loop gain of the FOG is proposed. By using a perturbation square wave to measure the loop gain of the FOG and adding an automatic gain control loop in the conventional control loop of the FOG, we successfully obtain the actual loop gain and make the loop gain converge to the reference value. The experimental results show that in the case of 20% variation in the loop gain, the dither residuals are successfully eliminated and the standard deviation of the FOG sampling outputs is decreased from 2.00  deg/h to 0.62  deg/h (sampling period 2.5 ms, 10 points smoothing). With this method, the loop gain of the FOG can be stabilized over the operation temperature range and in the long-time application, which provides a solid foundation for the engineering applications of the high-precision FOG. PMID:27409016

  6. Polarization-insensitive optical gain characteristics of highly stacked InAs/GaAs quantum dots

    SciTech Connect

    Kita, Takashi; Suwa, Masaya; Kaizu, Toshiyuki; Harada, Yukihiro

    2014-06-21

    The polarized optical gain characteristics of highly stacked InAs/GaAs quantum dots (QDs) with a thin spacer layer fabricated on an n{sup +}-GaAs (001) substrate were studied in the sub-threshold gain region. Using a 4.0-nm-thick spacer layer, we realized an electronically coupled QD superlattice structure along the stacking direction, which enabled the enhancement of the optical gain of the [001] transverse-magnetic (TM) polarization component. We systematically studied the polarized electroluminescence properties of laser devices containing 30 and 40 stacked InAs/GaAs QDs. The net modal gain was analyzed using the Hakki-Paoli method. Owing to the in-plane shape anisotropy of QDs, the polarization sensitivity of the gain depends on the waveguide direction. The gain showing polarization isotropy between the TM and transverse-electric polarization components is high for the [110] waveguide structure, which occurs for higher amounts of stacked QDs. Conversely, the isotropy of the [−110] waveguide is easily achieved even if the stacking is relatively low, although the gain is small.

  7. Calculation of the gain coefficient in cryogenically cooled Yb : YAG disks at high heat generation rates

    SciTech Connect

    Vadimova, O L; Mukhin, I B; Kuznetsov, I I; Palashov, O V; Perevezentsev, E A; Khazanov, Efim A

    2013-03-31

    We have calculated the stored energy and gain coefficient in disk gain elements cooled to cryogenic temperatures. The problem has been solved with allowance for intense heat generation, amplified spontaneous emission and parasitic lasing, without averaging over any spatial coordinate. The numerical simulation results agree well with experimental data, in particular at high heat generation rates. Experimental data and theoretical analysis indicate that composite disk gain elements containing an undoped region can store considerably more energy due to suppression of amplified spontaneous emission and parasitic lasing. (extreme light fields and their applications)

  8. Performance studies of high gain photomultiplier having Z-configuration of microchannel plates

    NASA Astrophysics Data System (ADS)

    Lo, C. C.; Leskovar, B.

    1980-11-01

    The characteristics of a high gain type ITT F4129 photomultiplier having three microchannel plates in cascade for electron multiplications were investigated. These plates are in the Z-configuration. Measurements are given of the gain dark current, cathode quantum efficiency, anode pulse linearity, electron transit time, single and multiphoton time spreads, fatigue, and pulse height resolution. The gain as a function of transverse magnetic field was measured and discussed. Photomultiplier characteristics as a function of the input pulse repetition frequency were also investigated and discussed.

  9. Gain in the non-steady-state free-electron laser

    SciTech Connect

    Wu, D.; Min, Y.

    1995-09-01

    The non-steady-state self-consistent equation in the linear regime of the free-electron laser (FEL) and the low gain formulas in the non-steady-state FEL are derived in this paper. It is found that due to slippage the nonuniformity effect in the longitudinal distribution of the electron beam density is dominant in the influence of the electron pulse length on the gain of the FEL. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. Second Harmonic FEL Oscillation

    NASA Astrophysics Data System (ADS)

    Neil, George R.; Benson, S. V.; Biallas, G.; Gubeli, J.; Jordan, K.; Myers, S.; Shinn, M. D.

    2001-08-01

    We have produced and measured for the first time second harmonic oscillation in the infrared region by a free electron laser. Although such lasing is ideally forbidden, since the gain of a plane wave is zero on axis for an electron beam perfectly aligned with a wiggler, a transverse mode antisymmetry allows sufficient gain in this experiment for lasing to occur. We lased at pulse rates up to 74.85 MHz and could produce over 4.5 W average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM01 mode.

  11. Shock ignition: a new approach to high gain inertial confinement fusion on the national ignition facility.

    PubMed

    Perkins, L J; Betti, R; LaFortune, K N; Williams, W H

    2009-07-24

    Shock ignition, an alternative concept for igniting thermonuclear fuel, is explored as a new approach to high gain, inertial confinement fusion targets for the National Ignition Facility (NIF). Results indicate thermonuclear yields of approximately 120-250 MJ may be possible with laser drive energies of 1-1.6 MJ, while gains of approximately 50 may still be achievable at only approximately 0.2 MJ drive energy. The scaling of NIF energy gain with laser energy is found to be G approximately 126E (MJ);{0.510}. This offers the potential for high-gain targets that may lead to smaller, more economic fusion power reactors and a cheaper fusion energy development path. PMID:19659364

  12. Entanglement, EPR correlations, and mesoscopic quantum superposition by the high-gain quantum injected parametric amplification

    SciTech Connect

    Caminati, Marco; De Martini, Francesco; Perris, Riccardo; Secondi, Veronica; Sciarrino, Fabio

    2006-12-15

    We investigate the multiparticle quantum superposition and the persistence of bipartite entanglement of the output field generated by the quantum injected high-gain optical parametric amplification of a single photon. The physical configuration based on the optimal universal quantum cloning has been adopted to investigate how the entanglement and the quantum coherence of the system persists for large values of the nonlinear parametric gain g.

  13. Graphene/GaSe-Nanosheet Hybrid: Towards High Gain and Fast Photoresponse.

    PubMed

    Lu, Rongtao; Liu, Jianwei; Luo, Hongfu; Chikan, Viktor; Wu, Judy Z

    2016-01-01

    While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 10(7) has been obtained simitaneously with a dynamic response time of around 10 ms for both light on and off. We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices. PMID:26776942

  14. Graphene/GaSe-Nanosheet Hybrid: Towards High Gain and Fast Photoresponse

    NASA Astrophysics Data System (ADS)

    Lu, Rongtao; Liu, Jianwei; Luo, Hongfu; Chikan, Viktor; Wu, Judy Z.

    2016-01-01

    While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 107 has been obtained simitaneously with a dynamic response time of around 10 ms for both light on and off. We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices.

  15. Graphene/GaSe-Nanosheet Hybrid: Towards High Gain and Fast Photoresponse

    PubMed Central

    Lu, Rongtao; Liu, Jianwei; Luo, Hongfu; Chikan, Viktor; Wu, Judy Z.

    2016-01-01

    While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 107 has been obtained simitaneously with a dynamic response time of around 10 ms for both light on and off. We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices. PMID:26776942

  16. Feedback Requirements for SASE-FELs

    SciTech Connect

    Loos, Henrik; /SLAC

    2012-07-06

    The operation of a Self Amplified Spontaneous Emission (SASE) Free Electron Lasers (FEL) at soft and hard X-ray wavelengths driven by a high brightness electron beam imposes strong requirements on the stability of the accelerator and feedback systems are necessary to both guarantee saturation of the SASE process as well as a stable photon beam for user experiments. Diagnostics for the relevant transverse and longitudinal beam parameters are presented and various examples of feedback systems for bunches with low repetition rate as well as systems for intra bunch train feedbacks are discussed.

  17. Effect of free electron laser (FEL) irradiation on tooth dentine

    NASA Astrophysics Data System (ADS)

    Ogino, Seiji; Awazu, Kunio; Tomimasu, Takio

    1996-12-01

    Free electron laser (FEL) gives high efficiency for the photo-induced effects when the laser is tuned to the absorption maximum of target materials. The effect on dentine was investigated using the FEL tuned to 9.4 micrometers , which is an absorption maximum of phosphoric acid in infrared region. As a result, irradiated dentine surface which was amorphous had changed to the recrystalized structure by the spectroscopic analysis of IR absorption and x-ray diffraction. Furthermore, the atomic ratio of P/Ca had reduced from 0.65 to 0.60. These results indicated that 9.4micrometers -FEL irradiation caused the selective ablation of phosphoric acid ion and the reconstruction of disordered atoms.

  18. An efficient high power microwave source at 35 GHz using an induction linac free electron accelerator

    SciTech Connect

    Clark, J.C.; Orzechowski, T.J.; Yarema, S.M.

    1986-11-01

    The Electron Laser Facility (ELF) is a free-electron laser (FEL) amplifier operating in the millimeter-wave regime. ELF uses the electron beam produced by the Experimental Test Accelerator (ETA), which is a linear-induction accelerator. We discuss here (1) the experimental results reflecting the high-peak-power output and high-extraction efficiency obtained from an FEL amplifier operated with a tapered wiggler magnetic field and (2) the results of studies of the exponential gain and saturated power obtained from an FEL amplifier with a flat wiggler while we parametrically varied the input power to the amplifier and the beam current into the wiggler.

  19. Statistical Analysis of Crossed Undulator for Polarization Control in a SASE FEL

    SciTech Connect

    Ding, Yuantao; Huang, Zhirong; /SLAC

    2008-02-01

    There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. In this paper, we study the crossed undulator scheme (K.-J. Kim, Nucl. Instrum. Methods A 445, 329 (2000)) for rapid polarization control in a self-amplified spontaneous emission (SASE) free electron laser (FEL). Because a SASE source is a temporally chaotic light, we perform a statistical analysis on the state of polarization using FEL theory and simulations. We show that by adding a small phase shifter and a short (about 1.3 times the FEL power gain length), 90{sup o} rotated planar undulator after the main SASE planar undulator, one can obtain circularly polarized light--with over 80% polarization--near the FEL saturation.

  20. Free-electron-laser (FEL)-induced desorption of ions from tooth dentine

    NASA Astrophysics Data System (ADS)

    Ogino, Seiji; Awazu, Kunio; Tomimasu, Takio

    1997-05-01

    Free electron laser (FEL) with the wide wavelength tunability has been developed and used for various applications. The FEL gives high efficiency for the photo- induced ablation when the laser is tuned to an absorption maximum of the target. This study investigates the FEL induced desorption of ions from tooth dentine to find new possibility for laser dentistry. The FEL was tuned to 9.4 (Mu) m, which is an absorption maximum of phosphoric acid ion known as major component of dentine. The FEL pulse length was several ps. The output average power was varied from 5 to 20mW by filters. A time-of-flight mass spectroscopy systems were developed for the purpose of analyzing the desorbed ions of varying masses. After the 9.4 micrometers FEL irradiation, the dentine surface was ablated, and visible light emission was observed. As a result, positive ions which correspond to Na+ and many phosphoric acid ions were measured. The positive ions, however were not observed when the FEL was not tuned to the absorption peak of the target. Therefore, this wavelength dependence points to resonant multiphoton vibrational excitation of molecules by the 9.4 micrometers FEL irradiation.

  1. Azimuthally unstable resonators for high-power CO[sub 2] lasers with annular gain media

    SciTech Connect

    Ehrlichmann, D.; Habich, U.; Plum, H.D.; Loosen, P.; Herziger, G. )

    1994-06-01

    Stable-unstable resonators have proved suitable for the extraction of a high-quality beam from a gain area that consists of a rectangular slab. Such gain areas have two substantially different transverse dimensions, and the resonators are stable in the small dimension while unstable in the larger one. Using off-axis unstable resonators avoids a central beam obscuration and improves beam quality. The adaptation of stable-unstable resonators to annular gain areas is described in this paper. The resulting resonators are stable in the radial direction and unstable in the azimuthal direction. Different unstable resonators, wound to match the annular geometry, are presented. The resonator modes are calculated numerically using a 3D-diffraction code that considers gain and misalignment. Resonator design parameters are obtained from a geometrical description of the resonator. Experimental results from a diffusion-cooled CO[sub 2] laser confirm theoretical predictions and show that the resonators are capable of extracting beams that are nearly diffraction-limited with high efficiency from an annular gain medium. Output powers of 2 kW have been obtained from a gain length of 1.8 m.

  2. The PixFEL project: Progress towards a fine pitch X-ray imaging camera for next generation FEL facilities

    NASA Astrophysics Data System (ADS)

    Rizzo, G.; Batignani, G.; Benkechkache, M. A.; Bettarini, S.; Casarosa, G.; Comotti, D.; Dalla Betta, G.-F.; Fabris, L.; Forti, F.; Grassi, M.; Lodola, L.; Malcovati, P.; Manghisoni, M.; Mendicino, R.; Morsani, F.; Paladino, A.; Pancheri, L.; Paoloni, E.; Ratti, L.; Re, V.; Traversi, G.; Vacchi, C.; Verzellesi, G.; Xu, H.

    2016-07-01

    The INFN PixFEL project is developing the fundamental building blocks for a large area X-ray imaging camera to be deployed at next generation free electron laser (FEL) facilities with unprecedented intensity. Improvement in performance beyond the state of art in imaging instrumentation will be explored adopting advanced technologies like active edge sensors, a 65 nm node CMOS process and vertical integration. These are the key ingredients of the PixFEL project to realize a seamless large area focal plane instrument composed by a matrix of multilayer four-side buttable tiles. In order to minimize the dead area and reduce ambiguities in image reconstruction, a fine pitch active edge thick sensor is being optimized to cope with very high intensity photon flux, up to 104 photons per pixel, in the range from 1 to 10 keV. A low noise analog front-end channel with this wide dynamic range and a novel dynamic compression feature, together with a low power 10 bit analog to digital conversion up to 5 MHz, has been realized in a 110 μm pitch with a 65 nm CMOS process. Vertical interconnection of two CMOS tiers will be also explored in the future to build a four-side buttable readout chip with high density memories. In the long run the objective of the PixFEL project is to build a flexible X-ray imaging camera for operation both in burst mode, like at the European X-FEL, or in continuous mode with the high frame rates anticipated for future FEL facilities.

  3. Alumni Networks--"An Untapped Potential to Gain and Retain Highly-Skilled Workers?"

    ERIC Educational Resources Information Center

    David, Alexandra; Coenen, Frans

    2014-01-01

    In times of increasing skills shortage, regions and particularly non-core regions, need to attract highly-skilled workers. It is better for these regions to (re)attract highly-skilled workers that gained knowledge and contacts elsewhere and because they once lived in the region for study have already ties to the university region than trying to…

  4. Development of low read noise high conversion gain CMOS image sensor for photon counting level imaging

    NASA Astrophysics Data System (ADS)

    Seo, Min-Woong; Kawahito, Shoji; Kagawa, Keiichiro; Yasutomi, Keita

    2016-05-01

    A CMOS image sensor with deep sub-electron read noise and high pixel conversion gain has been developed. Its performance is recognized through image outputs from an area image sensor, confirming the capability of photoelectroncounting- level imaging. To achieve high conversion gain, the proposed pixel has special structures to reduce the parasitic capacitances around FD node. As a result, the pixel conversion gain is increased due to the optimized FD node capacitance, and the noise performance is also improved by removing two noise sources from power supply. For the first time, high contrast images from the reset-gate-less CMOS image sensor, with less than 0.3e- rms noise level, have been generated at an extremely low light level of a few electrons per pixel. In addition, the photon-counting capability of the developed CMOS imager is demonstrated by a measurement, photoelectron-counting histogram (PCH).

  5. Dielectric wakefield accelerator to drive to the future FEL light sourcei.

    SciTech Connect

    Power, J.G.; Zholents, A.; Jing, C.; Kanareykin, A. )

    2011-01-01

    X-ray free-electron lasers (FELs) are expensive instruments and the accelerator holds the largest portion of the cost of the entire facility. Using a high-energy gain dielectric wake-field accelerator (DWA) instead of the conventional accelerator may facilitate reduction of the facility size and significant cost saving. We show that a collinear dielectric wake-field accelerator can, in principle, accelerate low charge and high peak current electron bunches to a few GeV energy with up to 100 kHz bunch repetition rate. Several such accelerators can share the same tunnel and same CW superconducting linac (operating with a few MHz bunch repetition rate) whose sole purpose is feeding the DWAs with wake producing low energy, high charge electron bunches with a desirable periodicity. Then, ten or more x-ray FELs can operate independently, each using its own linac. In this paper, we present an initial case study of a single stage 850 GHz DWA based on a quartz tube with a {approx}100MV/m loaded gradient sufficient to accelerate a 50 pC main electron beam to 2.4 GeV at a 100 kHz bunch repetition rate in just under 30 meters.

  6. Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

    SciTech Connect

    MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES; HJALMARSON,HAROLD P.; BACA,ALBERT G.; THORNTON,R.L.; DONALDSON,R.D.

    1999-12-17

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer that is very effective in the suppression of filament formation, alleviating current crowding. Damage-free operation is now possible with virtually infinite expected lifetime at much higher current levels than before. The inherent damage-free current capacity of the bulk GaAs itself depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approx}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs, unlike a switch with conventional contacts. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.

  7. Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

    SciTech Connect

    Baca, A.G.; Brown, D.J.; Donaldson, R.D.; Helgeson, W.D.; Hjalmarson, H.P.; Loubriel, G.M.; Mar, A.; O'Malley, M.W.; Thornton, R.L.; Zutavern, F.J.

    1999-08-05

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 50 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer beneath the PCSS contacts which is very effective in the suppression of filament formation and alleviating current crowding to improve the longevity of PCSS. Virtually indefinite, damage-free operation is now possible at much higher current levels than before. The inherent damage-free current capacity of the switch depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approximately}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.

  8. Application of variable-gain output feedback for high-alpha control

    NASA Technical Reports Server (NTRS)

    Ostroff, Aaron J.

    1990-01-01

    A variable-gain, optimal, discrete, output feedback design approach that is applied to a nonlinear flight regime is described. The flight regime covers a wide angle-of-attack range that includes stall and post stall. The paper includes brief descriptions of the variable-gain formulation, the discrete-control structure and flight equations used to apply the design approach, and the high performance airplane model used in the application. Both linear and nonlinear analysis are shown for a longitudinal four-model design case with angles of attack of 5, 15, 35, and 60 deg. Linear and nonlinear simulations are compared for a single-point longitudinal design at 60 deg angle of attack. Nonlinear simulations for the four-model, multi-mode, variable-gain design include a longitudinal pitch-up and pitch-down maneuver and high angle-of-attack regulation during a lateral maneuver.

  9. Dynamic properties of a pulse-pumped fiber laser with a short, high-gain cavity

    NASA Astrophysics Data System (ADS)

    Yang, Chaolin; Guo, Junhong; Wei, Pu; Wan, Hongdan; Xu, Ji; Wang, Jin

    2016-09-01

    We demonstrate a pulsed high-gain all-fiber laser without intracavity modulators, where a short and heavily Erbium-doped fiber is used as the gain medium in a ring cavity. By pulsed-pumping this short high gain cavity and tuning an intracavity variable optical coupler, the laser generates optical pulses with a pulse-width of μs at a repetition rate in the order of kHz down to one-shot operation. Furthermore, dynamic properties of this laser are investigated theoretically based on a traveling-wave-model, in which an adaptive-discrete-grid-finite-difference-method is applied. The simulation results validate the experimental results. The demonstrated pulsed laser is compact, flexible and cost-effective, which will have great potential for applications in all-optical sensing and communication systems.

  10. Recent progress in high gain InAs avalanche photodiodes (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Bank, Seth; Maddox, Scott J.; Sun, Wenlu; Nair, Hari P.; Campbell, Joe C.

    2015-08-01

    InAs possesses nearly ideal material properties for the fabrication of near- and mid-infrared avalanche photodiodes (APDs), which result in strong electron-initiated impact ionization and negligible hole-initiated impact ionization [1]. Consequently, InAs multiplication regions exhibit several appealing characteristics, including extremely low excess noise factors and bandwidth independent of gain [2], [3]. These properties make InAs APDs attractive for a number of near- and mid-infrared sensing applications including remote gas sensing, light detection and ranging (LIDAR), and both active and passive imaging. Here, we discuss our recent advances in the growth and fabrication of high gain, low noise InAs APDs. Devices yielded room temperature multiplication gains >300, with much reduced (~10x) lower dark current densities. We will also discuss a likely key contributor to our current performance limitations: silicon diffusion into the intrinsic (multiplication) region from the underlying n-type layer during growth. Future work will focus on increasing the intrinsic region thickness, targeting gains >1000. This work was supported by the Army Research Office (W911NF-10-1-0391). [1] A. R. J. Marshall, C. H. Tan, M. J. Steer, and J. P. R. David, "Electron dominated impact ionization and avalanche gain characteristics in InAs photodiodes," Applied Physics Letters, vol. 93, p. 111107, 2008. [2] A. R. J. Marshall, A. Krysa, S. Zhang, A. S. Idris, S. Xie, J. P. R. David, and C. H. Tan, "High gain InAs avalanche photodiodes," in 6th EMRS DTC Technical Conference, Edinburgh, Scotland, UK, 2009. [3] S. J. Maddox, W. Sun, Z. Lu, H. P. Nair, J. C. Campbell, and S. R. Bank, "Enhanced low-noise gain from InAs avalanche photodiodes with reduced dark current and background doping," Applied Physics Letters, vol. 101, no. 15, pp. 151124-151124-3, Oct. 2012.

  11. The GALAXIE all-optical FEL project

    SciTech Connect

    Rosenzweig, J. B.; Arab, E.; Andonian, G.; Cahill, A.; Fitzmorris, K.; Fukusawa, A.; Hoang, P.; Jovanovic, I.; Marcus, G.; Marinelli, A.; Murokh, A.; Musumeci, P.; Naranjo, B.; O'Shea, B.; O'Shea, F.; Ovodenko, A.; Pogorelsky, I.; Putterman, S.; Roberts, K.; Shumail, M.; and others

    2012-12-21

    We describe a comprehensive project, funded under the DARPA AXiS program, to develop an all-optical table-top X-ray FEL based on dielectric acceleration and electromagnetic undulators, yielding a compact source of coherent X-rays for medical and related applications. The compactness of this source demands that high field (>GV/m) acceleration and undulation-inducing fields be employed, thus giving rise to the project's acronym: GV/m AcceLerator And X-ray Integrated Experiment (GALAXIE). There are numerous physics and technical hurdles to surmount in this ambitious scenario, and the integrated solutions include: a biharmonic photonic TW structure, 200 micron wavelength electromagnetic undulators, 5 {mu}m laser development, ultra-high brightness magnetized/asymmetric emittance electron beam generation, and SASE FEL operation. We describe the overall design philosophy of the project, the innovative approaches to addressing the challenges presented by the design, and the significant progress towards realization of these approaches in the nine months since project initialization.

  12. UV FEL Processing - A Unique Opportunity

    NASA Astrophysics Data System (ADS)

    Kelley, Michael J.

    1996-05-01

    The ability of UV light to transfrom materials was recognized in the early years of this century. Ever since, its use for processing has been re-investigated each time a new UV light source technology has become available. Especially exciting results in the surface modi- fication of metals and polymers, and in micromachining were found with the short, intense, single-wavelength pulses from excimer lasers. However, as with previous advances, the cost of excimer laser light and their maximum unit size limited their commercialization to high value applications, mostly in medicine and electronics manufacturing. An analysis of the demonstrated potential mass applications suggests that the horizon for commercialization appears to be at an energy cost below 0.5 cents/kJ of light and at a unit capacity above 10 kW. An analysis of light source technologies points to a free electron laser (FEL) based on a superconducting radiofrequency (SRF) accelerator as the only real prospect for reaching this goal. The FEL's picosecond pulse length and high peak power offer further advantages for micro- machining. Progress is being made toward a 1 kW technology demonstration.

  13. Comparative analysis of the intrinsic voltage gain and unit gain frequency between SOI and bulk FinFETs up to high temperatures

    NASA Astrophysics Data System (ADS)

    Oliveira, Alberto Vinicius de; Agopian, Paula Ghedini Der; Martino, Joao Antonio; Simoen, Eddy; Claeys, Cor; Collaert, Nadine; Thean, Aaron

    2016-09-01

    This paper presents an experimental analysis of the analog application figures of merit: the intrinsic voltage gain (AV) and unit gain frequency, focusing on the performance comparison between silicon triple gate pFinFET devices, which were processed on both Si and Silicon-On-Insulator (SOI) substrates. The high temperature (from 25 °C to 150 °C) influence and different channel lengths and fin widths were also taken into account. While the temperature impact on the intrinsic voltage gain (AV) is limited, the unit gain frequency was strongly affected due to the carrier mobility degradation at higher temperatures, for both p- and n-type FinFET structures. In addition, the pFinFETs showed slightly larger AV values compared to the n-type counterparts, whereby the bulk FinFETs presented a higher dispersion than the SOI FinFETs.

  14. Development of thin-film total-reflection mirrors for the XUV FEL

    NASA Astrophysics Data System (ADS)

    Jacobi, Sandra; Wiesmann, Joerg; Steeg, Barbara; Feldhaus, Josef; Michaelsen, Carsten

    2001-12-01

    A free electron laser for the XUV spectral range is currently under test at the TESLA Test Facility at DESY. High gain has been demonstrated below 100nm wavelength, and it is expected that the FEL will provide intense, sub-picosecond radiation pulses with photon energies up to 200eV. Thin film optical elements required for this facility are currently being developed by the X-ray optics group of the GKSS research center near Hamburg. Sputter-deposited coatings have been prepared for the use as total reflection X-ray mirrors for FEL beam optics. Coatings of low Z elements with the lowest possible absorption and high reflectivity have been investigated. Silicon substrates have been coated with carbon using different deposition conditions. The films were investigated using the soft X-ray reflectometer at the HASYLAB beamline G1. The measurements show that the reflectivity of the films is typically 90% at energies below 200eV and a grazing incidence angle of 4 degrees. The optical constants of these coatings obtained from the reflectivity measurements and are in agreement with tabulated values. The deposition parameters have been optimized resulting in argon contamination free films with near-theoretical performance. Preliminary investigations concerning the heat resistance of the films were also carried out.

  15. Maintaining a High Physical Activity Level Over 20 Years and Weight Gain

    PubMed Central

    Hankinson, Arlene L.; Daviglus, Martha L.; Bouchard, Claude; Carnethon, Mercedes; Lewis, Cora E.; Schreiner, Pamela J.; Liu, Kiang; Sidney, Stephen

    2013-01-01

    Context Data supporting physical activity guidelines to prevent long-term weight gain are sparse, particularly during the period when the highest risk of weight gain occurs. Objective To evaluate the relationship between habitual activity levels and changes in body mass index (BMI) and waist circumference over 20 years. Design, Setting, and Participants The Coronary Artery Risk Development in Young Adults (CARDIA) study is a prospective longitudinal study with 20 years of follow-up, 1985-86 to 2005-06. Habitual activity was defined as maintaining high, moderate, and low activity levels based on sex-specific tertiles of activity scores at baseline. Participants comprised a population-based multi-center cohort (Chicago, Illinois; Birmingham, Alabama; Minneapolis, Minnesota; and Oakland, California) of 3554 men and women aged 18 to 30 years at baseline. Main Outcome Measures Average annual changes in BMI and waist circumference Results Over 20 years, maintaining high levels of activity was associated with smaller gains in BMI and waist circumference compared with low activity levels after adjustment for race, baseline BMI, age, education, cigarette smoking status, alcohol use, and energy intake. Men maintaining high activity gained 2.6 fewer kilograms (+ 0.15 BMI units per year; 95 % confidence interval [CI] 0.11-0.18 vs +0.20 in the lower activity group; 95% CI, 0.17-0.23) and women maintaining higher activity gained 6.1 fewer kilograms (+0.17 BMI units per year; 95 % CI, 0.12-0.21 vs. +0.30 in the lower activity group; 95 % CI, 0.25-0.34). Men maintaining high activity gained 3.1 fewer centimeters in waist circumference (+0.52 cm per year; 95 % CI, 0.43-0.61 cm vs 0.67 cm in the lower activity group; 95 % CI, 0.60-0.75) and women maintaining higher activity gained 3.8 fewer centimeters (+0.49 cm per year; 95 % CI, 0.39-0.58 vs 0.67 cm in the lower activity group; 95 % CI, 0.60-0.75). Conclusion Maintaining high activity levels through young adulthood may lessen

  16. High hyperdiploid childhood acute lymphoblastic leukemia: Chromosomal gains as the main driver event.

    PubMed

    Paulsson, Kajsa

    2016-01-01

    High hyperdiploid childhood acute lymphoblastic leukemia is characterized by multiple chromosomal gains. Recent results show that this subtype harbors relatively few genetic abnormalities besides the extra chromosomes, which appear to arise early and are likely the main driver event. Secondary hits primarily target genes in the rat sarcoma (RAS) signaling pathway and histone modifiers. PMID:27308574

  17. 75 FR 61228 - Board Meeting: Technical Lessons Gained From High-Level Nuclear Waste Disposal Efforts

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-04

    ... REVIEW BOARD Board Meeting: Technical Lessons Gained From High-Level Nuclear Waste Disposal Efforts... 1987, the U.S. Nuclear Waste Technical Review Board will meet in Dulles, Virginia, on October 26, 2010... technical issues and to review the technical validity of DOE activities related to implementing the...

  18. High hyperdiploid childhood acute lymphoblastic leukemia: Chromosomal gains as the main driver event

    PubMed Central

    Paulsson, Kajsa

    2016-01-01

    ABSTRACT High hyperdiploid childhood acute lymphoblastic leukemia is characterized by multiple chromosomal gains. Recent results show that this subtype harbors relatively few genetic abnormalities besides the extra chromosomes, which appear to arise early and are likely the main driver event. Secondary hits primarily target genes in the rat sarcoma (RAS) signaling pathway and histone modifiers. PMID:27308574

  19. High-Current Gain Two-Dimensional MoS₂-Base Hot-Electron Transistors.

    PubMed

    Torres, Carlos M; Lan, Yann-Wen; Zeng, Caifu; Chen, Jyun-Hong; Kou, Xufeng; Navabi, Aryan; Tang, Jianshi; Montazeri, Mohammad; Adleman, James R; Lerner, Mitchell B; Zhong, Yuan-Liang; Li, Lain-Jong; Chen, Chii-Dong; Wang, Kang L

    2015-12-01

    The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications. PMID:26524388

  20. Attainment of a high gain in a disk amplifying stage with neodymium phosphate glass elements

    SciTech Connect

    Voronich, Ivan N; Garanin, Sergey G; Zaretskii, Aleksei I; Ignat'ev, Ivan V; Kirillov, G A; Murugov, Vasilii M; Osin, Vladimir A; Sukharev, Stanislav A; Charukhchev, Aleksandr V

    2004-06-30

    An efficient reflecting coating made of a MIRO foil with an oxide layer is fabricated, which enhances the reflection of radiation of pump lamps in the head of a high-power neodymium laser and allows a gain g{sub 0}=5x10{sup -2} cm{sup -1} to be achieved. (lasers)

  1. INSIGHTS GAINED AS A RESULT OF A HIGH SCHOOL SOCIAL STUDIES COURSE.

    ERIC Educational Resources Information Center

    LALOR, IDA B.

    A STUDY ATTEMPTED TO DETERMINE WHETHER HIGH SCHOOL STUDENTS WHO HAVE GAINED KNOWLEDGE AND UNDERSTANDING OF CONCEPTS IN ANTHROPOLOGY WOULD--(1) ACHIEVE GREATER SELF-INSIGHT, (2) BECOME LESS ETHNOCENTRIC IN THEIR ATTITUDES TOWARD OTHERS, AND (3) INCREASE THEIR ABILITY TO THINK CRITICALLY ABOUT SOCIAL PROBLEMS. A 1-YEAR EXPERIMENTAL COURSE ON WORLD…

  2. Deployment/retraction mechanism for solar maximum mission high gain antenna system

    NASA Technical Reports Server (NTRS)

    Bennett, N.; Preiswerk, P.

    1979-01-01

    A mechanism called a deployment/retraction assembly (DRA) which provides not only a stable, but a deployable platform for the high gain antenna system (HGAS) aboard the Solar Maximum Mission (SMM) spacecraft is described. The DRA also has the capability to retract the system upon command.

  3. Prior exercise training blunts short-term high-fat diet-induced weight gain.

    PubMed

    Snook, Laelie A; MacPherson, Rebecca E K; Monaco, Cynthia M F; Frendo-Cumbo, Scott; Castellani, Laura; Peppler, Willem T; Anderson, Zachary G; Buzelle, Samyra L; LeBlanc, Paul J; Holloway, Graham P; Wright, David C

    2016-08-01

    High-fat diets rapidly cause weight gain and glucose intolerance. We sought to determine whether these changes could be mitigated with prior exercise training. Male C57BL/6J mice were exercise-trained by treadmill running (1 h/day, 5 days/wk) for 4 wk. Twenty-four hours after the final bout of exercise, mice were provided with a high-fat diet (HFD; 60% kcal from lard) for 4 days, with no further exercise. In mice fed the HFD prior to exercise training, the results were blunted weight gain, reduced fat mass, and a slight attenuation in glucose intolerance that was mirrored by greater insulin-induced Akt phosphorylation in skeletal muscle compared with sedentary mice fed the HFD. When ad libitum-fed sedentary mice were compared with sedentary high-fat fed mice that were calorie restricted (-30%) to match the weight gain of the previously trained high-fat fed mice, the same attenuated impairments in glucose tolerance were found. Blunted weight gain was associated with a greater capacity to increase energy expenditure in trained compared with sedentary mice when challenged with a HFD. Although mitochondrial enzymes in white adipose tissue and UCP-1 protein content in brown adipose tissue were increased in previously exercised compared with sedentary mice fed a HFD, ex vivo mitochondrial respiration was not increased in either tissue. Our data suggest that prior exercise training attenuates high-fat diet-induced weight gain and glucose intolerance and is associated with a greater ability to increase energy expenditure in response to a high-fat diet. PMID:27101294

  4. Long wavelength, high gain InAsSb strained-layer superlattice photoconductive detectors

    DOEpatents

    Biefeld, Robert M.; Dawson, L. Ralph; Fritz, Ian J.; Kurtz, Steven R.; Zipperian, Thomas E.

    1991-01-01

    A high gain photoconductive device for 8 to 12 .mu.m wavelength radiation including an active semiconductor region extending from a substrate to an exposed face, the region comprising a strained-layer superlattice of alternating layers of two different InAs.sub.1-x Sb.sub.x compounds having x>0.75. A pair of spaced electrodes are provided on the exposed face, and changes in 8 to 12 .mu.m radiation on the exposed face cause a large photoconductive gain between the spaced electrodes.

  5. High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host

    DOEpatents

    Comaskey, Brian J.; Ault, Earl R.; Kuklo, Thomas C.

    2005-07-05

    A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

  6. The crucial fiber components and gain fiber for high power ytterbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Liao, Lei; Liu, Peng; Xing, Ying-Bin; Wang, Yi-Bo; Dai, Neng-Li; Li, Jin-Yan; He, Bing; Zhou, Jun

    2015-08-01

    We have demonstrated a kW continuous-wave ytterbium-doped all-fiber laser oscillator with 7×1 fused fiber bundle combiner, fiber Bragg grating (FBG) and double-clad gain fiber fabricated by corresponding technologies. The results of experiment that the oscillator had operated at 1079.48nm with 80.94% slope efficiency without the influence of temperature and non-linear effects indicate that fiber components and gain fiber were suitable to high power environment. No evidence of the signal power roll-over showed that this oscillator possess the capacity to highest output with available pump power.

  7. Control of the polarization of a vacuum-ultraviolet, high-gain, free-electron laser

    DOE PAGESBeta

    Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; Finetti, Paola; Mahieu, Benoît; Viefhaus, Jens; Zangrando, Marco; De Ninno, Giovanni; Lambert, Guillaume; Ferrari, Eugenio; et al

    2014-12-02

    The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independentmore » instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.« less

  8. Control of the polarization of a vacuum-ultraviolet, high-gain, free-electron laser

    SciTech Connect

    Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; Finetti, Paola; Mahieu, Benoît; Viefhaus, Jens; Zangrando, Marco; De Ninno, Giovanni; Lambert, Guillaume; Ferrari, Eugenio; Buck, Jens; Ilchen, Markus; Vodungbo, Boris; Mahne, Nicola; Svetina, Cristian; Spezzani, Carlo; Di Mitri, Simone; Penco, Giuseppe; Trovó, Mauro; Fawley, William M.; Rebernik, Primoz R.; Gauthier, David; Grazioli, Cesare; Coreno, Marcello; Ressel, Barbara; Kivimäki, Antti; Mazza, Tommaso; Glaser, Leif; Scholz, Frank; Seltmann, Joern; Gessler, Patrick; Grünert, Jan; De Fanis, Alberto; Meyer, Michael; Knie, André; Moeller, Stefan P.; Raimondi, Lorenzo; Capotondi, Flavio; Pedersoli, Emanuele; Plekan, Oksana; Danailov, Miltcho B.; Demidovich, Alexander; Nikolov, Ivaylo; Abrami, Alessandro; Gautier, Julien; Lüning, Jan; Zeitoun, Philippe; Giannessi, Luca

    2014-12-02

    The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independent instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.

  9. High current gain 4H-SiC bipolar junction transistor

    NASA Astrophysics Data System (ADS)

    Yourun, Zhang; Jinfei, Shi; Ying, Liu; Chengchun, Sun; Fei, Guo; Bo, Zhang

    2016-04-01

    A novel 4H-SiC BJT of high current gain with a suppressing surface traps effect has been proposed. It is effective to improve the current gain due to the lower electrons density in the surface region by extending the emitter metal to overlap the passivation layer on the extrinsic base surface. The electrons trapped in the extrinsic base surface induce the degeneration of SiC BJTs device performance. By modulating the electron recombination rate, the novel structure can increase the current gain to 63.2% compared with conventional ones with the compatible process technology. Optimized sizes are an overlapped metal length of 4 μm, as well as an oxide layer thickness of 50 nm. Project supported by the National Natural Science Foundation of China (Nos. 61306093, 61401075).

  10. The 'SuperFET' - A monolithic device for high-gain amplifiers

    NASA Astrophysics Data System (ADS)

    Crescenzi, E. J., Jr.; Wilser, W. T.; Oglesbee, R. W.; Algeri, S. J.

    1981-07-01

    The development of minimum area GaAs FET chips which resulted in ICs with two FETs on a single .7 sq mm chip linked with microstrip matching circuitry is described. Cost considerations are given, noting that the figure of merit was high due to matching elements covering over half of the total chip area. The gain for the X- and Ku-bands over discrete transistors were 6 and 5 dB, at 20 and 18 GHz respectively. Design objectives for the X-band IC of 7-12.5 GHz minimum bandwidth, multistage cascadability for amplifier gains in the 25 to 50 dB range, low VSWR gain flatness, and cost competitiveness with thin film discrete FETs were achieved. The Ku-band 'superFET' was designed for small size, application flexibility, and mechanical ruggedness and reliability, with an eye to EW military applications.

  11. Super ACO FEL oscillation at 300 nm

    NASA Astrophysics Data System (ADS)

    Nutarelli, D.; Garzella, D.; Renault, E.; Nahon, L.; Couprie, M. E.

    2000-05-01

    Some recent improvements, involving both the optical cavity mirrors and the positron beam dynamics in the storage ring, have allowed us to achieve a laser oscillation at 300 nm on the Super ACO Storage Ring FEL. The Super ACO storage ring is operated at 800 MeV which is the nominal energy for the usual synchrotron radiation users, and the highest energy for a storage ring FEL. The lasing at 300 nm could be kept during 2 h per injection, with a stored current ranging between 30 and 60 mA. The FEL characteristics are presented here. The longitudinal stability and the FEL optics behaviour are also discussed.

  12. High gain/broadband oxide glasses for next generation Raman amplifiers

    NASA Astrophysics Data System (ADS)

    Rivero, Clara A.

    Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are larger and the operating wavelength is fixed only by the pump wavelength and the bandwidth of the Raman active medium. In this context, glasses are the material of choice for this application due to their relatively broad spectral response, and ability of making them into optical fiber. This dissertation summarizes findings on different oxide-based glasses that have been synthesized and characterized for their potential application as Raman gain media. Two main glass families were investigated: phosphate-based glass matrices for broadband Raman gain application and TeO2-based glasses for high Raman gain amplification. A phosphate network was preferred for the broadband application since the phosphate Raman active modes can provide amplification above 1000 cm-1, whilst TeO2-based glasses were selected for the high gain application due to their enhanced nonlinearities and polarizabilities among the other oxide-based network formers. The results summarized in this dissertation show that phosphate-based glasses can provide Raman amplification bandwidths of up to 40 THz, an improvement of almost 5 times the bandwidth of SiO2. On the other hand, tellurite-based glasses appear to be promising candidates for high gain discrete Raman applications, providing peak Raman gain coefficients of up to 50 times higher than SiO 2, at 1064 nm. Although, visible spontaneous Raman scattering cross-section measurement is the most frequently used tool for estimating the strength and spectral distribution of Raman gain in materials, especially glasses, there are some issues that one needs to be

  13. High gain, Fast Scan, Broad Spectrum Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM

    SciTech Connect

    OHara, David

    2009-05-08

    During contract # DE-FG02-ER83545, Parallax Research, Inc. developed a High gain, Fast Scan Broad Spectrum Parallel beam Wavelength Dispersive X-ray Spectrometer for use on Scanning Electron Microscopes (SEM). This new spectrometer allows very fast high resolution elemental analysis of samples in an electron microscope. By comparison to previous WDS spectrometers, it can change from one energy position to another very quickly and has an extended range compared to some similar products.

  14. Output characteristics of SASE-driven short wavelength FEL`s

    SciTech Connect

    Fawley, W.M.

    1997-02-01

    This paper investigates various properties of the ``microspikes`` associated with self-amplified spontaneous emission (SASE) in a short wavelength free-electron laser (FEL). Using results from the 2-D numerical simulation code GINGER, we confirm theoretical predictions such as the convective group velocity in the exponential gain regime. In the saturated gain regime beyond the initial saturation, we find that the average radiation power continues to grow with an approximately linearly dependence upon undulator length. Moreover, the spectrum significantly broadens and shifts in wavelength to the redward direction, with{ital P(w)} approaching a constant, asymptotic value. This is in marked contrast to the exponential gain regime where the spectrum steadily narrows, {ital P(w)} grows, and the central wavelength remains constant with {ital z}. Via use of a spectrogram diagnostic {ital S(w,t)}, it appears that the radiation pattern in the saturated gain regime is composed of an ensemble of distinct ``sinews`` whose widths AA remain approximately constant but whose central wavelengths can ``chirp`` by varying a small extent with {ital t}.

  15. Properties of high gain GaAs switches for pulsed power applications

    SciTech Connect

    Zutavern, F.J.; Loubriel, G.M.; Hjalmarson, H.P.; Mar, A.; Helgeson, W.D.; O`Malley, M.W.; Ruebush, M.H.; Falk, R.A.

    1997-09-01

    High gain GaAs photoconductive semiconductor switches (PCSS) are being used in a variety of electrical and optical short pulse applications. The highest power application, which the authors are developing, is a compact, repetitive, short pulse linear induction accelerator. The array of PCSS, which drive the accelerator, will switch 75 kA and 250 kV in 30 ns long pulses at 50 Hz. The accelerator will produce a 700 kV, 7kA electron beam for industrial and military applications. In the low power regime, these switches are being used to switch 400 A and 5 kV to drive laser diode arrays which produce 100 ps optical pulses. These short optical pulses are for military and commercial applications in optical and electrical range sensing, 3D laser radar, and high speed imaging. Both types of these applications demand a better understanding of the switch properties to increase switch lifetime, reduce jitter, optimize optical triggering, and improve overall switch performance. These applications and experiments on the fundamental behavior of high gain GaAs switches will be discussed. Open shutter, infra-red images and time-resolved images of the current filaments, which form during high gain switching, will be presented. Results from optical triggering experiments to produce multiple, diffuse filaments for high current repetitive switching will be described.

  16. Efficiency optimization in a FEL with fields` nonadiabatic tapering

    SciTech Connect

    Goncharov, I.A.; Belyavskiy, E.D.; Silivra, A.A.

    1995-12-31

    Amplification of an electromagnetic wave in free electron lasers with a reversed guide field and right-hand polarized wiggler field is investigated both analytically and numerically. An effect of electron bunch trapping by the high frequency electromagnetic field is used for efficiency optimization. On the basis of motion stability criteria a possibility of bunches trapping by FEL parameters nonadiabatic (experimentally realizable) tapering is shown. The stability analysis of electron motion is based on Lyapunov theory for autonomy systems. A particle simulation is carried out for FEL parameters close to the experimental ones (relativistic factor {gamma}=4.75, wiggler field strength B{sub w}= 2.8 kG, guide field strength B{sub o}= -1.4 kG, operation wavelength {lambda}=6.2 mm) for the case of wiggler field tapering. Theoretically predicted rule of wiggler field tapering corresponding to FEL efficiency of 55% is approximated by stepped functions. For the experimentally realizable tapering it is found that FEL efficiency can be over 40%.

  17. Suppression of parasitics and pencil beams in the high-gain National Ignition Facility multipass preamplifier

    NASA Astrophysics Data System (ADS)

    Moran, Bryan D.; Dane, C. Brent; Crane, John K.; Martinez, Mikael D.; Penko, Frank A.; Hackel, Lloyd A.

    1998-06-01

    The multi-pass amplifier (MPA) is the last subsystem of the NIF preamplifier, which feeds the main amplification stages of the NIF beamline. The MPA is based on a flashlamp pumped 5-cm diameter by 48 cm long Nd:glass rod amplifier operated at a single pass small signal gain of 15 to 17. The MPA is an off-axis multi-pass image relayed system, which uses two gain isolating image relaying telescopes and passive polarization switching using a Faraday rotator to output the pulse. We describe the MPA system, techniques used to avoid parasitic oscillation at high gain, and suppression of pencil beams. The system is used to generate a well- conditioned 22-joule output from one millijoule input. The output pulse requirements include 22 joules in a square, flat topped beam, and with near field spatial contrast of <5% RMS, square pulse temporal distortion <2.3, and an RMS energy stability of <3%. All of these requirements have been exceeded. The largest impediment to successful operation was overcoming parasitic oscillation. Sources of oscillation could be generally divided into two categories: those due to birefringence, which compromised the polarization contrast of the system; and those due to unwanted reflections from optical surfaces. Baffling in the vacuum spatial filters helps to control the system sensitivity to unwanted stray reflections from flat AR coated surfaces. Stress birefringence in the rather large glass volume of the rod (942 cm3) and the four vacuum loaded lenses are significant, as each of these elements is double passed between each polarizing beam splitter pass. This lowers the polarization contrast of the system, which can prevent the system from operating at sufficient gain. Careful analysis and layout of the MPA architecture has allowed us to address the challenges posed by a system small signal gain of approximately equals 33000 and with an output pulse of as high as 27 joules.

  18. Electron bunch length measurement at the Vanderbilt FEL

    SciTech Connect

    Amirmadhi, F.; Brau, C.A.; Mendenhall, M.

    1995-12-31

    During the past few years, a number of experiments have been performed to demonstrate the possibility to extract the longitudinal charge distribution from spectroscopic measurements of the coherent far-infrared radiation emitted as transition radiation or synchrotron radiation. Coherent emission occurs in a spectral region where the wavelength is comparable to or longer than the bunch length, leading to an enhancement of the radiation intensity that is on the order of the number of particles per bunch, as compared to incoherent radiation. This technique is particularly useful in the region of mm and sub-mm bunch lengths, a range where streak-cameras cannot be used for beam diagnostics due to their limited time resolution. Here we report on experiments that go beyond the proof of principle of this technique by applying it to the study and optimization of FEL performance. We investigated the longitudinal bunch length of the Vanderbilt FEL by analyzing the spectrum of coherent transition radiation emitted by the electron bunches. By monitoring the bunch length while applying a bunch-compression technique, the amount of the compression could be easily observed. This enabled us to perform a systematic study of the FEL performance, especially gain and optical pulse width, as a function of the longitudinal electron distribution in the bunch. The results of this study will be presented and discussed.

  19. The PixFEL project: development of advanced X-ray pixel detectors for application at future FEL facilities

    NASA Astrophysics Data System (ADS)

    Rizzo, G.; Comotti, D.; Fabris, L.; Grassi, M.; Lodola, L.; Malcovati, P.; Manghisoni, M.; Ratti, L.; Re, V.; Traversi, G.; Vacchi, C.; Batignani, G.; Bettarini, S.; Casarosa, G.; Forti, F.; Morsani, F.; Paladino, A.; Paoloni, E.; Dalla Betta, G.-F.; Pancheri, L.; Verzellesi, G.; Xu, H.; Mendicino, R.; Benkechkache, M. A.

    2015-02-01

    The PixFEL project aims to develop an advanced X-ray camera for imaging suited for the demanding requirements of next generation free electron laser (FEL) facilities. New technologies can be deployed to boost the performance of imaging detectors as well as future pixel devices for tracking. In the first phase of the PixFEL project, approved by the INFN, the focus will be on the development of the microelectronic building blocks, carried out with a 65 nm CMOS technology, implementing a low noise analog front-end channel with high dynamic range and compression features, a low power ADC and high density memory. At the same time PixFEL will investigate and implement some of the enabling technologies to assembly a seamless large area X-ray camera composed by a matrix of multilayer four-side buttable tiles. A pixel matrix with active edge will be developed to minimize the dead area of the sensor layer. Vertical interconnection of two CMOS tiers will be explored to build a four-side buttable readout chip with small pixel pitch and all the on-board required functionalities. The ambitious target requirements of the new pixel device are: single photon resolution, 1 to 104 photons @ 1 keV to 10 keV input dynamic range, 10-bit analog to digital conversion up to 5 MHz, 1 kevent in-pixel memory and 100 μm pixel pitch. The long term goal of PixFEL will be the development of a versatile X-ray camera to be operated either in burst mode (European XFEL), or in continuous mode to cope with the high frame rates foreseen for the upgrade phase of the LCLS-II at SLAC.

  20. Investigations of SBS and laser gain competition in high-power phase modulated fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Flores, Angel; Dajani, Iyad; Hult, Dane; Robin, Craig

    2014-02-01

    We present experimental results of SBS suppression in high power, monolithic, Yb-doped fiber amplifiers via phase modulated laser gain competition. To narrow the linewidth, two-tone laser gain competition between broad (1036 nm) and narrow linewidth (1064 nm) laser signals is investigated in conjunction with phase modulation and yields pump limited output powers of 600 W. Here integration of both two-tone and pseudo random bit sequence (PRBS) phase modulation concepts, generated SBS enhancement factors of greater than 17x at a modulation frequency of 500 MHz, without reaching the SBS threshold. Significantly, the results represent a near order of magnitude reduction in linewidth over current high-power, monolithic, Yb-doped fiber amplifiers.

  1. High-gain backup antenna design for Pioneer Venus Orbiter spacecraft

    NASA Technical Reports Server (NTRS)

    Glaser, J. I.

    1986-01-01

    The development and performance is described of a high-gain antenna designed to serve on the Pioneer Venus Orbiter spacecraft as a backup to the principal high-gain antenna unit in the unlikely event the mechanically despun antenna mechanism malfunctioned. The final design, a center-fed standing wave array of six sleeve dipoles enclosed in a fiber glass radome, performed successfully, as did all the antennas, on the Pioneer Orbiter spacecraft which was launched on May 20, 1978, as part of the Pioneer Venus mission. Photographs of experimental models giving details of design and construction are included, as well as graphs showing measured pattern and impedance matching characteristics of the subject antenna.

  2. An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

    SciTech Connect

    Höppner, H.; Tanikawa, T.; Schulz, M.; Riedel, R.; Teubner, U.; Faatz, B.; Tavella, F.

    2015-05-15

    High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to many hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.

  3. Generation of nearly hemispherical and high gain azimuthally symmetric patterns with printed circuit antennas

    NASA Astrophysics Data System (ADS)

    Yang, Hung Yu; Alexopoulos, Nicolaos G.

    1987-08-01

    Patttern shaping techniques are discussed for printed circuit antennas such as microstrip dipoles and slot elements. Crossed printed circuit dipoles or a combination of a printed circuit dipole and a slot are employed. It is demonstrated that with the proper choice of substrate or substrate-superstrate parameters it is possible to generate: (1) nearly hemispherical patterns, (2) high-gain azimuthally symmetric patterns, and (3) nearly sec theta patterns.

  4. On the ignition of high gain thermonuclear microexplosions with electric pulse power

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2004-02-01

    It was recently shown that the ignition of thermonuclear microexplosions seems possible with two Marx generators of modest size, one with a high current lower voltage for compression and confinement, and one with a high voltage lower current for ignition, transmitting their energy to the thermonuclear target by two nested magnetically insulated transmission lines. Here it is shown in much greater detail how this concept has the potential for the ignition of high gain thermonuclear microexplosions with a yield sufficiently low for a thermonuclear reactor and rocket propulsion. The concept also offers the possibility for the concurrent burn of deuterium-tritium with natural uranium or thorium.

  5. Recent developments in CrystFEL 1

    PubMed Central

    White, Thomas A.; Mariani, Valerio; Brehm, Wolfgang; Yefanov, Oleksandr; Barty, Anton; Beyerlein, Kenneth R.; Chervinskii, Fedor; Galli, Lorenzo; Gati, Cornelius; Nakane, Takanori; Tolstikova, Alexandra; Yamashita, Keitaro; Yoon, Chun Hong; Diederichs, Kay; Chapman, Henry N.

    2016-01-01

    CrystFEL is a suite of programs for processing data from ‘serial crystallography’ experiments, which are usually performed using X-ray free-electron lasers (FELs) but also increasingly with other X-ray sources. The CrystFEL software suite has been under development since 2009, just before the first hard FEL experiments were performed, and has been significantly updated and improved since then. This article describes the most important improvements which have been made to CrystFEL since the first release version. These changes include the addition of new programs to the suite, the ability to resolve ‘indexing ambiguities’ and several ways to improve the quality of the integrated data by more accurately modelling the underlying diffraction physics. PMID:27047311

  6. Trigeminal high-frequency stimulation produces short- and long-term modification of reflex blink gain

    PubMed Central

    Ryan, Michael; Kaminer, Jaime; Enmore, Patricia

    2013-01-01

    Reflex blinks provide a model system for investigating motor learning in normal and pathological states. We investigated whether high-frequency stimulation (HFS) of the supraorbital branch of the trigeminal nerve before the R2 blink component (HFS-B) decreases reflex blink gain in alert rats. As with humans (Mao JB, Evinger C. J Neurosci 21: RC151, 2001), HFS-B significantly reduced blink size in the first hour after treatment for rats. Repeated days of HFS-B treatment produced long-term depression of blink circuits. Blink gain decreased exponentially across days, indicating a long-term depression of blink circuits. Additionally, the HFS-B protocol became more effective at depressing blink amplitude across days of treatment. This depression was not habituation, because neither long- nor short-term blink changes occurred when HFS was presented after the R2. To investigate whether gain modifications produced by HFS-B involved cerebellar networks, we trained rats in a delay eyelid conditioning paradigm using HFS-B as the unconditioned stimulus and a tone as the conditioned stimulus. As HFS-B depresses blink circuits and delay conditioning enhances blink circuit activity, occlusion should occur if they share neural networks. Rats acquiring robust eyelid conditioning did not exhibit decreases in blink gain, whereas rats developing low levels of eyelid conditioning exhibited weak, short-term reductions in blink gain. These results suggested that delay eyelid conditioning and long-term HFS-B utilize some of the same cerebellar circuits. The ability of repeated HFS-B treatment to depress trigeminal blink circuit activity long term implied that it may be a useful protocol to reduce hyperexcitable blink circuits that underlie diseases like benign essential blepharospasm. PMID:24285868

  7. Physics design for the ATA tapered wiggler 10. 6. mu. FEL amplifier experiment

    SciTech Connect

    Fawley, W.M.

    1985-10-01

    We are presently designing and constructing a high-gain, tapered wiggler 10.6 ..mu.. FEL amplifier to operate with the 50 MeV ATA e-beam. The initial experiments will be done with a constant period (lambda /SUB w/ =8 cm), 5 m-long linear wiggler. For an input laser power of 800 MW and electron beam brightness of 2.10/sup 5/ A/(rad-cm)/sup 2/, we hope to achieve a trapped particle fraction about0.5 and an energy extraction efficiency of about2% with a about10% taper in the wiggler magnetic field. This taper corresponds to decelerating the trapped particle approximately two full ponderomotive well (i.e. bucket) heights. In this talk, we discuss the physics motivations behind our tapered wiggler design and initial experimental diagnostics.

  8. Integrated computer simulation on FIR FEL dynamics

    SciTech Connect

    Furukawa, H.; Kuruma, S.; Imasaki, K.

    1995-12-31

    An integrated computer simulation code has been developed to analyze the RF-Linac FEL dynamics. First, the simulation code on the electron beam acceleration and transport processes in RF-Linac: (LUNA) has been developed to analyze the characteristics of the electron beam in RF-Linac and to optimize the parameters of RF-Linac. Second, a space-time dependent 3D FEL simulation code (Shipout) has been developed. The RF-Linac FEL total simulations have been performed by using the electron beam data from LUNA in Shipout. The number of particles using in a RF-Linac FEL total simulation is approximately 1000. The CPU time for the simulation of 1 round trip is about 1.5 minutes. At ILT/ILE, Osaka, a 8.5MeV RF-Linac with a photo-cathode RF-gun is used for FEL oscillation experiments. By using 2 cm wiggler, the FEL oscillation in the wavelength approximately 46 {mu}m are investigated. By the simulations using LUNA with the parameters of an ILT/ILE experiment, the pulse shape and the energy spectra of the electron beam at the end of the linac are estimated. The pulse shape of the electron beam at the end of the linac has sharp rise-up and it slowly decays as a function of time. By the RF-linac FEL total simulations with the parameters of an ILT/ILE experiment, the dependencies of the start up of the FEL oscillations on the pulse shape of the electron beam at the end of the linac are estimated. The coherent spontaneous emission effects and the quick start up of FEL oscillations have been observed by the RF-Linac FEL total simulations.

  9. The Jefferson lab FEL driver ERLs

    SciTech Connect

    Douglas, David R.; Tennant, Christopher D.

    2013-11-01

    Jefferson Lab has - for over a decade - been operating high power IR and UV FELs using CW energy recovering linacs based on DC photocathode electron sources and CEBAF SRF technology. These machines have unique combinations of beam quality, power, and operational flexibility, and thus offer significant opportunity for experiments that use low and medium energy (several tens - few hundreds of MeV) electron beams. We will describe the systems and detail their present and near-term (potential) performance. Recent internal-target analysis and validation testing will be discussed, and schemes for single- and two-pass fixed target operation described. An introduction to subsequent discussions of beam quality and upgrade paths to polarized operation/higher energy will be given.

  10. Gate Controlled Photocurrent Generation Mechanisms in High-Gain In₂Se₃ Phototransistors.

    PubMed

    Island, J O; Blanter, S I; Buscema, M; van der Zant, H S J; Castellanos-Gomez, A

    2015-12-01

    Photocurrent in photodetectors incorporating van der Waals materials is typically produced by a combination of photocurrent generation mechanisms that occur simultaneously during operation. Because of this, response times in these devices often yield to slower, high gain processes, which cannot be turned off. Here we report on photodetectors incorporating the layered material In2Se3, which allow complete modulation of a high gain, photogating mechanism in the ON state in favor of fast photoconduction in the OFF state. While photoconduction is largely gate independent, photocurrent from the photogating effect is strongly modulated through application of a back gate voltage. By varying the back gate, we demonstrate control over the dominant mechanism responsible for photocurrent generation. Furthermore, because of the strong photogating effect, these direct-band gap, multilayer phototransistors produce ultrahigh gains of (9.8 ± 2.5) × 10(4) A/W and inferred detectivities of (3.3 ± 0.8) × 10(13) Jones, putting In2Se3 among the most sensitive 2D materials for photodetection studied to date. PMID:26540135

  11. Enhancing speed of pinning synchronizability: low-degree nodes with high feedback gains

    NASA Astrophysics Data System (ADS)

    Zhou, Ming-Yang; Zhuo, Zhao; Liao, Hao; Fu, Zhong-Qian; Cai, Shi-Min

    2015-12-01

    Controlling complex networks is of paramount importance in science and engineering. Despite recent efforts to improve controllability and synchronous strength, little attention has been paid to the speed of pinning synchronizability (rate of convergence in pinning control) and the corresponding pinning node selection. To address this issue, we propose a hypothesis to restrict the control cost, then build a linear matrix inequality related to the speed of pinning controllability. By solving the inequality, we obtain both the speed of pinning controllability and optimal control strength (feedback gains in pinning control) for all nodes. Interestingly, some low-degree nodes are able to achieve large feedback gains, which suggests that they have high influence on controlling system. In addition, when choosing nodes with high feedback gains as pinning nodes, the controlling speed of real systems is remarkably enhanced compared to that of traditional large-degree and large-betweenness selections. Thus, the proposed approach provides a novel way to investigate the speed of pinning controllability and can evoke other effective heuristic pinning node selections for large-scale systems.

  12. Enhancing speed of pinning synchronizability: low-degree nodes with high feedback gains

    PubMed Central

    Zhou, Ming-Yang; Zhuo, Zhao; Liao, Hao; Fu, Zhong-Qian; Cai, Shi-Min

    2015-01-01

    Controlling complex networks is of paramount importance in science and engineering. Despite recent efforts to improve controllability and synchronous strength, little attention has been paid to the speed of pinning synchronizability (rate of convergence in pinning control) and the corresponding pinning node selection. To address this issue, we propose a hypothesis to restrict the control cost, then build a linear matrix inequality related to the speed of pinning controllability. By solving the inequality, we obtain both the speed of pinning controllability and optimal control strength (feedback gains in pinning control) for all nodes. Interestingly, some low-degree nodes are able to achieve large feedback gains, which suggests that they have high influence on controlling system. In addition, when choosing nodes with high feedback gains as pinning nodes, the controlling speed of real systems is remarkably enhanced compared to that of traditional large-degree and large-betweenness selections. Thus, the proposed approach provides a novel way to investigate the speed of pinning controllability and can evoke other effective heuristic pinning node selections for large-scale systems. PMID:26626045

  13. Design of high-gain, wideband antenna using microwave hyperbolic metasurface

    NASA Astrophysics Data System (ADS)

    Zhao, Yan

    2016-05-01

    In this work, we apply hyperbolic metasurfaces (HMSs) to design high-gain and wideband antennas. It is shown that HMSs formed by a single layer of split-ring resonators (SRRs) can be excited to generate highly directive beams. In particular, we suggest two types of the SRR-HMS: a capacitively loaded SRR (CLSRR)-HMS and a substrate-backed double SRR (DSRR)-HMS. Both configurations ensure that the periodicity of the structures is sufficiently small for satisfying the effective medium theory. For the antenna design, we propose a two-layer-stacked configuration for the 2.4 GHz frequency band based on the DSRR-HMS excited by a folded monopole. Measurement results confirm numerical simulations and demonstrate that an antenna gain of more than 5 dBi can be obtained for the frequency range of 2.1 - 2.6 GHz, with a maximum gain of 7.8 dBi at 2.4 GHz.

  14. Enhancing speed of pinning synchronizability: low-degree nodes with high feedback gains.

    PubMed

    Zhou, Ming-Yang; Zhuo, Zhao; Liao, Hao; Fu, Zhong-Qian; Cai, Shi-Min

    2015-01-01

    Controlling complex networks is of paramount importance in science and engineering. Despite recent efforts to improve controllability and synchronous strength, little attention has been paid to the speed of pinning synchronizability (rate of convergence in pinning control) and the corresponding pinning node selection. To address this issue, we propose a hypothesis to restrict the control cost, then build a linear matrix inequality related to the speed of pinning controllability. By solving the inequality, we obtain both the speed of pinning controllability and optimal control strength (feedback gains in pinning control) for all nodes. Interestingly, some low-degree nodes are able to achieve large feedback gains, which suggests that they have high influence on controlling system. In addition, when choosing nodes with high feedback gains as pinning nodes, the controlling speed of real systems is remarkably enhanced compared to that of traditional large-degree and large-betweenness selections. Thus, the proposed approach provides a novel way to investigate the speed of pinning controllability and can evoke other effective heuristic pinning node selections for large-scale systems. PMID:26626045

  15. A bootstrapped, low-noise, and high-gain photodetector for shot noise measurement

    SciTech Connect

    Zhou, Haijun; Yang, Wenhai; Li, Zhixiu; Li, Xuefeng; Zheng, Yaohui

    2014-01-15

    We presented a low-noise, high-gain photodetector based on the bootstrap structure and the L-C (inductance and capacitance) combination. Electronic characteristics of the photodetector, including electronic noise, gain and frequency response, and dynamic range, were verified through a single-frequency Nd:YVO{sub 4} laser at 1064 nm with coherent output. The measured shot noise of 50 μW laser was 13 dB above the electronic noise at the analysis frequency of 2 MHz, and 10 dB at 3 MHz. And a maximum clearance of 28 dB at 2 MHz was achieved when 1.52 mW laser was illuminated. In addition, the photodetector showed excellent linearities for both DC and AC amplifications in the laser power range between 12.5 μW and 1.52 mW.

  16. High gain broadband amplification of ultraviolet pulses in optical parametric chirped pulse amplifier.

    PubMed

    Wnuk, Paweł; Stepanenko, Yuriy; Radzewicz, Czesław

    2010-04-12

    We report on a high gain amplification of broadband ultraviolet femtosecond pulses in an optical parametric chirped pulse amplifier. Broadband ultraviolet seed pulses were obtained by an achromatic frequency doubling of the output from a femtosecond Ti:Sapphire oscillator. Stretched seed pulses were amplified in a multipass parametric amplifier with a single BBO crystal pumped by a ns frequency quadrupled Nd:YAG laser. A noncollinear configuration was used for a broadband amplification. The total (after compression) amplification of 2.510(5) was achieved, with compressed pulse energy of 30 microJ and pulse duration of 24 fs. We found that the measured gain was limited by thermal effects induced by the absorption of the pump laser by color centers created in the BBO crystal. PMID:20588633

  17. High gain and low excess noise near infrared single photon avalanche detector

    NASA Astrophysics Data System (ADS)

    Linga, Krishna; Yevtukhov, Yuriy; Liang, Bing

    2009-05-01

    We present the discrete amplification approach used for development of a very high gain and low excess noise factor in the near infrared wavelength region. The devices have the following performance characteristics: gain > 2X105, excess noise factor < 1.05, rise time < 350ps, fall time < 500ps and operating voltage < 60V. In the photon counting mode, the devices can be operated in the non-gated mode under a constant DC bias and do not require any external quenching circuit. These devices are ideal for researchers in the fields of deep space optical communication, spectroscopy, industrial and scientific instrumentation, Ladar/Lidar, quantum cryptography, night vision and other military, defense and aerospace applications.

  18. Effects of Bandwidth, Compression Speed, and Gain at High Frequencies on Preferences for Amplified Music

    PubMed Central

    2012-01-01

    This article reviews a series of studies on the factors influencing sound quality preferences, mostly for jazz and classical music stimuli. The data were obtained using ratings of individual stimuli or using the method of paired comparisons. For normal-hearing participants, the highest ratings of sound quality were obtained when the reproduction bandwidth was wide (55 to 16000 Hz) and ripples in the frequency response were small (less than ± 5 dB). For hearing-impaired participants listening via a simulated five-channel compression hearing aid with gains set using the CAM2 fitting method, preferences for upper cutoff frequency varied across participants: Some preferred a 7.5- or 10-kHz upper cutoff frequency over a 5-kHz cutoff frequency, and some showed the opposite preference. Preferences for a higher upper cutoff frequency were associated with a shallow high-frequency slope of the audiogram. A subsequent study comparing the CAM2 and NAL-NL2 fitting methods, with gains slightly reduced for participants who were not experienced hearing aid users, showed a consistent preference for CAM2. Since the two methods differ mainly in the gain applied for frequencies above 4 kHz (CAM2 recommending higher gain than NAL-NL2), these results suggest that extending the upper cutoff frequency is beneficial. A system for reducing “overshoot” effects produced by compression gave small but significant benefits for sound quality of a percussion instrument (xylophone). For a high-input level (80 dB SPL), slow compression was preferred over fast compression. PMID:23172008

  19. Effects of bandwidth, compression speed, and gain at high frequencies on preferences for amplified music.

    PubMed

    Moore, Brian C J

    2012-09-01

    This article reviews a series of studies on the factors influencing sound quality preferences, mostly for jazz and classical music stimuli. The data were obtained using ratings of individual stimuli or using the method of paired comparisons. For normal-hearing participants, the highest ratings of sound quality were obtained when the reproduction bandwidth was wide (55 to 16000 Hz) and ripples in the frequency response were small (less than ± 5 dB). For hearing-impaired participants listening via a simulated five-channel compression hearing aid with gains set using the CAM2 fitting method, preferences for upper cutoff frequency varied across participants: Some preferred a 7.5- or 10-kHz upper cutoff frequency over a 5-kHz cutoff frequency, and some showed the opposite preference. Preferences for a higher upper cutoff frequency were associated with a shallow high-frequency slope of the audiogram. A subsequent study comparing the CAM2 and NAL-NL2 fitting methods, with gains slightly reduced for participants who were not experienced hearing aid users, showed a consistent preference for CAM2. Since the two methods differ mainly in the gain applied for frequencies above 4 kHz (CAM2 recommending higher gain than NAL-NL2), these results suggest that extending the upper cutoff frequency is beneficial. A system for reducing "overshoot" effects produced by compression gave small but significant benefits for sound quality of a percussion instrument (xylophone). For a high-input level (80 dB SPL), slow compression was preferred over fast compression. PMID:23172008

  20. Developing high-power hybrid resonant gain-switched thulium fiber lasers.

    PubMed

    Yan, Shuo; Wang, Yao; Zhou, Yan; Yang, Nan; Li, Yue; Tang, Yulong; Xu, Jianqiu

    2015-10-01

    In this paper, we propose hybrid-pumped resonant gain-switched thulium fiber lasers to realize high-average-power and high-pulse-energy 2-μm laser emissions. Based on numerical simulation, laser dynamics (pulse peak power, pulse energy, pulse duration, etc.) of this kind of laser system are investigated in detail. By taking advantages of the 793 nm continuous wave pump and the 1900 nm pulsed pump, performance of the laser emission can be significantly improved, with the highest average power of 28 W, peak power of 3.5 kW, pulse energy of 281 μJ, and narrowest pulse duration of 92 ns, all of which can be further optimized through designing the cavity parameters and the pumping circumstance. Compared with the pump pulses, two times improvement in pulse energy and average power has been achieved. This hybrid resonant gain-switched system has an all-fiber configuration and high efficiency (low heat load), and can be steadily extended into the cladding pump scheme, thus paving a new way to realize high power (>100 W average power) and high pulse energy (>1 mJ) 2 μm thulium fiber lasers. PMID:26480083

  1. Fat substitutes promote weight gain in rats consuming high-fat diets

    PubMed Central

    Swithers, Susan E.; Ogden, Sean B.; Davidson, Terry L.

    2011-01-01

    The use of food products designed to mimic the sensory properties of sweet and fat while providing fewer calories has been promoted as a method for reducing food intake and body weight. However, such products may interfere with one mechanism that animals use to regulate energy balance, a learned relationship between the sensory properites of food and the caloric consequences of consuming those foods. Consistent with this hypothesis, previous data have shown that providing rats with sweet tastes that are not associated with the delivery of calories using high-intensity sweeteners results in increased food intake, body weight and adiposity, but only if the diet on which they are maintained also tastes sweet. In the present experiment, we examined whether use of the fat substitute, olestra, would have similar consequences by comparing the effects of consuming high-fat, high-calorie potato chips to the effects of consuming potato chips that sometimes signalled high calories (using high-fat potato chips) and that sometimes signalled lower calories (using non-fat potato chips manufactured with the fat substitute olestra). The results demonstrated that food intake, body weight gain and adiposity were greater for rats that consumed both the high-calorie chips and the low-calorie chips with olestra compared to rats that consumed consuming only the high-calorie chips, but only if animals were also consuming a chow diet that was high in fat and calories. When animals were maintained on a low-fat chow diet, intake, weight gain, and adiposity did not differ significantly based on chip type. However, rats previously exposed to both the low-calorie chips with olestra and the high-calorie chips exhibited increased body weight gain, food intake and adiposity when they were provided with a high fat, high calorie chow diet, even though the potato chips were no longer available. This suggests that the experience with the chips containing olestra affected the ability to predict high

  2. Status and achievements at FERMI@Elettra: the first double cascade seeded EUV-SXR FEL facility open to users

    NASA Astrophysics Data System (ADS)

    Svetina, Cristian; Mahne, Nicola; Raimondi, Lorenzo; Rumiz, Luca; Zangrando, Marco; Allaria, Enrico; Bencivenga, Filippo; Callegari, Carlo; Capotondi, Flavio; Castronovo, Davide; Cinquegrana, Paolo; Craievich, Paolo; Cudin, Ivan; Dal Forno, Massimo; Danailov, Miltcho B.; D'Auria, Gerardo; De Monte, Raffaele; De Ninno, Giovanni; Demidovich, Alexander; Di Mitri, Simone; Diviacco, Bruno; Fabris, Alessandro; Fabris, Riccardo; Fawley, William M.; Ferianis, Mario; Ferrari, Eugenio; Froehlich, Lars; Furlan Radivo, Paolo; Gaio, Giulio; Giannessi, Luca; Kiskinova, Maya; Lonza, Marco; Mahieu, Benoit; Masciovecchio, Claudio; Nikolov, Ivaylo P.; Parmigiani, Fulvio; Pedersoli, Emanuele; Penco, Giuseppe; Predonzani, Mauro; Principi, Emiliano; Rossi, Fabio; Scafuri, Claudio; Serpico, Claudio; Sigalotti, Paolo; Spampinati, Simone; Spezzani, Carlo; Svandrlik, Michele; Trovo, Mauro; Vascotto, Alessandro; Veronese, Marco; Visintini, Roberto; Zangrando, Dino

    2013-09-01

    FERMI@Elettra is the first seeded VUV/soft X-ray FEL source. It is composed of two undulatory chains: the low energy branch (FELl) covering the wavelength range from 20 nm up to 100 nm, and the high energy branch (FEL2, employing a double stage cascade), covering the wavelength range from 4 nm up to 20 nm. At the end of 2012 FELl has been opened to external users while FEL2 has been turned on for the first time having demonstrated that a double cascade scheme is suitable for generating high intensity coherent FEL radiation. In this paper we will share our experience and will show our most recent results for both FERMI FELl and FEL2 sources. We will also present a brand new machine scheme that allows to perform two-colour pump and probe experiments as well as the first experimental results.

  3. Effects of high CO2 levels on dynamic photosynthesis: carbon gain, mechanisms, and environmental interactions.

    PubMed

    Tomimatsu, Hajime; Tang, Yanhong

    2016-05-01

    Understanding the photosynthetic responses of terrestrial plants to environments with high levels of CO2 is essential to address the ecological effects of elevated atmospheric CO2. Most photosynthetic models used for global carbon issues are based on steady-state photosynthesis, whereby photosynthesis is measured under constant environmental conditions; however, terrestrial plant photosynthesis under natural conditions is highly dynamic, and photosynthetic rates change in response to rapid changes in environmental factors. To predict future contributions of photosynthesis to the global carbon cycle, it is necessary to understand the dynamic nature of photosynthesis in relation to high CO2 levels. In this review, we summarize the current body of knowledge on the photosynthetic response to changes in light intensity under experimentally elevated CO2 conditions. We found that short-term exposure to high CO2 enhances photosynthetic rate, reduces photosynthetic induction time, and reduces post-illumination CO2 burst, resulting in increased leaf carbon gain during dynamic photosynthesis. However, long-term exposure to high CO2 during plant growth has varying effects on dynamic photosynthesis. High levels of CO2 increase the carbon gain in photosynthetic induction in some species, but have no significant effects in other species. Some studies have shown that high CO2 levels reduce the biochemical limitation on RuBP regeneration and Rubisco activation during photosynthetic induction, whereas the effects of high levels of CO2 on stomatal conductance differ among species. Few studies have examined the influence of environmental factors on effects of high levels of CO2 on dynamic photosynthesis. We identified several knowledge gaps that should be addressed to aid future predictions of photosynthesis in high-CO2 environments. PMID:27094437

  4. Low threshold photonic crystal laser based on a Rhodamine dye doped high gain polymer.

    PubMed

    Shi, Lan-Ting; Jin, Feng; Zheng, Mei-Ling; Dong, Xian-Zi; Chen, Wei-Qiang; Zhao, Zhen-Sheng; Duan, Xuan-Ming

    2016-02-21

    We demonstrate low threshold lasing oscillation in a photonic crystal (PhC) laser by using tert-butyl Rhodamine B (t-Bu-RhB) doped gain media. Lactonic t-Bu-RhB is synthesized to improve doping concentration in polymethylmethacrylate (PMMA) films, and then isomerized to the zwitterion form to achieve highly fluorescent gain medium. The t-Bu-RhB doped PMMA film is sandwiched by a pair of polystyrene colloidal crystals to construct a PhC resonating cavity. Single-mode laser oscillation at 592 nm is observed when the PhC resonating cavity is pumped by a Nd:YAG laser. The lasing threshold is 0.12 MW cm(-2) utilizing 6.9 wt% t-Bu-RhB doped PMMA films, which is only 1/60 of that with 3 wt% t-Bu-RhB doped PMMA films. The concentration-dependent lasing action is attributed to different gain factors of the t-Bu-RhB doped PMMA films. Furthermore, a spatially and spectrally coherent laser beam from the PhC resonating cavity is verified by exploring the far-field image and angular dependence of the lasing emission. The approach provides a facile and efficient strategy to reduce the lasing threshold for fabricating low threshold PhC lasers. PMID:26817423

  5. High-Protein Diet Improves Postoperative Weight Gain After Massive Small-Bowel Resection

    PubMed Central

    Sun, Raphael C.; Choi, Pamela M.; Diaz-Miron, Jose; Sommovilla, Joshua; Guo, Jun; Erwin, Christopher R.

    2016-01-01

    Introduction Short bowel syndrome (SBS) is a morbid clinical condition that results from massive small-bowel resection (SBR). After SBR, there is a dramatic weight loss in the acute postoperative period. Our aim was to determine the impact of a high-protein diet (HPD) on weight gain and body composition in mice after SBR. Methods C57BL/6 mice underwent 50 % proximal SBR. Postoperatively, mice were randomly selected to receive standard rodent liquid diet (LD) (n=6) or an isocaloric HPD (n=9) for 28 days. Mice weights were recorded daily. Body composition analyses were obtained weekly. Student's t test was used for statistical comparisons with p<0.05 considered significant. Results Mice that were fed HPD after SBR returned to baseline weight on average at postoperative day (POD) 8 versus mice that were fed LD that returned to baseline weight on average at POD 22. Total fat mass and lean mass were significantly greater by POD 14 within the HPD group. Both groups of mice demonstrated normal structural adaptation. Conclusion HPD results in greater weight gain and improved body composition in mice after SBR. This finding may be clinically important for patients with SBS since improved weight gain may reduce the time needed for parenteral nutrition. PMID:25519080

  6. High-gain optical Cherenkov oscillator driven by low-voltage electron beam

    SciTech Connect

    Smetanin, I.V.; Oraevsky, A.N.

    1995-12-31

    A novel scheme of high-gain optical (from IR up to UV) Cherenkov-type oscillator driven by low-voltage high-current electron beam is proposed in the present report. In the scheme discussed the magnetized electron beam propagates above the surface of absorbing medium of complex dielectric susceptibility {epsilon}{omega} = {epsilon}{sub 1}({omega}) + i{epsilon}{sub 2}({omega}), {epsilon}{sub 2}>0. We have found that at frequencies {omega} that {beta}{sup 2}> 2{epsilon}{sub 1}/{vert_bar}{epsilon}{vert_bar}{sup 2} ({beta} = v/c, v is the electron velocity), an amplification of co-propagating slow surface electromagnetic wave is possible. In contrast to the conventional Cherenkov oscillators, the absorption condition {epsilon}2>0 is crucial for the gain, which is absent for transparent medium. The physics of this amplification effect is analogous to that of electron beam dissipative instability. The wavelength generated is determined here by dielectric properties of the surface, and does not depend strongly on electron energy. Thus it is possible to use rather compact low voltage ({le} 1MeV) high-current accelerators as drivers. Optimum oscillation conditions are found to be at frequencies near the resonance absorption lines of surface material (i.e. from IR up to UV). The gain up to {approximately}0.5cm{sup -1} in the near IR ({approximately}10THz, SrF{sub 2} absorption line) is possible for 250keV high current (density {approximately}10{sup 12}cm{sup -3}) electron beam.

  7. Research on a novel high gain model for dispersive spectrographic systems

    NASA Astrophysics Data System (ADS)

    Cheng, Liang; Ye, Zi; Gong, Xingzhi; Yu, Feihong

    2008-03-01

    Traditional dispersive spectrographic systems usually base on slit imaging. The entrance slit can ensure a remarkable spectral resolution but a loss of system throughput and vice versa, thus this kind of instruments can't achieve Jacquinot advantage and Fellgett advantage simultaneously and statically. To derive a high gain model for the stationary dispersive systems with these two advantages, traditional single-slit and the multi-slit spectrographic systems were studied. A method for single channel spectrum abstraction in a multi-slit spectrographic system was derived. This method demonstrates that if each individual slit in a multi-slit system possesses a transformation form of orthogonal independent column codes, the spectrum of each individual slit can be abstracted from superposed spectrum, spectral resolution of equivalent single-slit system is obtained and the system achieves dual advantages. This high gain computational system model is applicable for almost all kinds of existing dispersive spectrographic systems. Furthermore individual coded slits can be integrated as a coded aperture to increase system's integration level and reduce off-axis aberration. Based on the derivation of theoretical model, two kinds of coding forms' mathematical models were studied. To verify the derived theory, a testing system with a specially designed flat-field holographic concave grating and a coded aperture of order 16 Hadamard matrix form was set up. The experiment indicated that although optical aberration and other system noise were involved, this high gain system model could still achieve a high spectral resolution of 0.4nm as single-slit system, while remarkable system etendue (8X) and SNR (4X) were also obtained, which proved the correctness of the theoretical derivation.

  8. An Analysis of Shot Noise Propagation and Amplificationin Harmonic Cascade FELs

    SciTech Connect

    Huang, Z.; /SLAC

    2006-12-11

    The harmonic generation process in a harmonic cascade (HC) FEL is subject to noise degradation which is proportional to the square of the total harmonic order. In this paper, we study the shot noise evolution in the first-stage modulator and radiator of a HC FEL that produces the dominant noise contributions. We derive the effective input noise for a modulator operating in the low-gain regime, and analyze the radiator noise for a density-modulated beam. The significance of these noise sources in different harmonic cascade designs is also discussed.

  9. UV-VUV mirrors for storage ring FELs: present performances and requirements

    NASA Astrophysics Data System (ADS)

    Garzella, David; Couprie, Marie-Emmanuelle; Billardon, Michel

    1996-08-01

    Storage ring FELs (SRFELs) recently demonstrated to be useful coherent light sources for applications in several branches of scientific research. In particular, the super ACO SRFEL provided UV light at 350 nm for successful operations in a time resolved fluorescence experiment on a biological molecule and in the first two color experiment combining synchrotron radiation and FEL light. Up to now, SRFELs are characterized by a relatively low gain and hence, great care must be invested on the choice of optical cavity mirrors. In this paper we relate the several characterizations performed on different set of mirrors and the obtained results.

  10. Picosecond pump-probe using an FEL and a synchrotron source

    SciTech Connect

    Denbeaux, G.; Straub, K.D.; Madey, J.M.J.

    1995-12-31

    Two color pump-probe experiments using both the Duke Storage Ring as a synchrotron light source for visible light the Mark III FEL as a tunable, high peak power IR source are possible. The visible synchrotron source can be used as a probe of vibrational excitation from the FEL in an experiment using vibrationally-assisted fluorescence as an indicator of overlap of the IR and the visible pulses. An optical delay line in the FEL beam will allow adjustment of the arrival time of the IR pulse relative to the visible probe. The storage ring RF booster and the Mark III FEL RF sources will be both driven by the same master oscillator with a timing jitter between sources of less than 20 psec. Exploration of coupling between electronic excitation and lifetimes of vibrational excitation of fluorescent compounds in solution can be carried out with this configuration.

  11. High Gain Antenna System Deployment Mechanism Integration, Characterization, and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Parong, Fil; Russell, Blair; Garcen, Walter; Rose, Chris; Johnson, Chris; Huber, Craig

    2014-01-01

    The integration and deployment testing of the High Gain Antenna System for the Global Precipitation Measurement mission is summarized. The HGAS deployment mechanism is described. The gravity negation system configuration and its influence on vertical, ground-based, deployment tests are presented with test data and model predictions. A focus is made on the late discovery and resolution of a potentially mission degrading deployment interference condition. The interaction of the flight deployment mechanism, gravity negation mechanism, and use of dynamic modeling is described and lessons learned presented.

  12. High Gain Antenna System Deployment Mechanism Integration, Characterization, and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Parong, Fil; Russell, Blair; Garcen, Walter; Rose, Chris; Johnson, Chris; Huber, Craig

    2014-01-01

    The integration and deployment testing of the High Gain Antenna System (HGAS) for the Global Precipitation Measurement mission is summarized. The HGAS deployment mechanism is described. The gravity negation system configuration and its influence on vertical, ground-based deployment tests are presented with test data and model predictions. A focus is made on the late discovery and resolution of a potentially mission-degrading deployment interference condition. The interaction of the flight deployment mechanism, gravity-negation mechanism, and use of dynamic modeling is described and lessons learned presented

  13. Howling canceling for high gain speakerphone systems exploiting the loudspeaker redundancy

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Yin, Qinye; Mu, Pengcheng; Song, Tianheng; Wang, Wei; Wu, Junchao

    2011-10-01

    Howling of an audio amplifying system is annoying, which may occur when a closed-loop is formed for amplified signals. In this paper, we exploit the space diversity offered by the loudspeaker redundancy and develop a new howling canceling approach for high gain speakerphone systems. The amplified waves are weighted at the two loudspeakers to achieve self-cancellation at the microphone after the propagation. As a result, the echo waves can be completely eliminated at the microphone, which avoids any feedback that yields the howling. Results of simulation and hardware test show effectiveness of the method.

  14. Sub-Poissonian shot noise of a high internal gain injection photon detector.

    PubMed

    Memis, Omer Gokalp; Katsnelson, Alex; Kong, Soon-Cheol; Mohseni, Hooman; Yan, Minjun; Zhang, Shuang; Hossain, Tim; Jin, Niu; Adesida, Ilesanmi

    2008-08-18

    The noise performance of an infrared injection photon detector with very high internal gain was investigated at a wavelength of 1.55 mum. The devices showed sub-Poissonian shot noise with Fano factors around 0.55 at 0.7 V at room temperature. Optical to electrical conversion factors of 3000 electrons per absorbed photon were recorded at 0.7 V. The change in noise-equivalent power with respect to bias voltage was evaluated. The optical to electrical conversion factor and Fano factor were measured under increasing illumination and compared to theoretical expectations. PMID:18711508

  15. ONT High Gain Initiative WRAP (Wide Area Rapid Acoustic Prediction) computational performance section

    SciTech Connect

    McGraw, J.R.; Hedstrom, G.; De Groot, T.

    1990-10-02

    LLNL received a contract during March 1990 to perform three tasks for ONT. This letter report covers Task I which concerned a supercomputing effort in a program termed the High Gain Initiative, which is an anti-submarine (ASW) project that requires substantial computational and signal processing expertise. The core of the computational aspects at the present time is a code called WRAP (Wide Area Rapid Acoustic Prediction). LLNL's objective was to study the WRAP model and determine the feasibility and limits of its optimization. At the present time, the WRAP code runs on a single processor VAX computer.

  16. Method and system for modulation of gain suppression in high average power laser systems

    DOEpatents

    Bayramian, Andrew James

    2012-07-31

    A high average power laser system with modulated gain suppression includes an input aperture associated with a first laser beam extraction path and an output aperture associated with the first laser beam extraction path. The system also includes a pinhole creation laser having an optical output directed along a pinhole creation path and an absorbing material positioned along both the first laser beam extraction path and the pinhole creation path. The system further includes a mechanism operable to translate the absorbing material in a direction crossing the first laser beam extraction laser path and a controller operable to modulate the second laser beam.

  17. Multi-modelling as new estimation schema for high-gain observers

    NASA Astrophysics Data System (ADS)

    Bernat, Jakub; Stepien, Slawomir

    2015-06-01

    The presented paper proposes a novel method of observer design. A new two-layer observer structure is introduced. The first layer consists of multiple high-gain observers. The latter is built to connect the first layer observers into single one. As the new contribution, the new mapping is defined between an unknown state and measurable outputs allowing to explore new estimation schema. Hence, the proposed method enhances the estimation process for linear and nonlinear systems. Furthermore, it is shown that the introduced observation scheme improves the transients. Illustrative examples are calculated to show the properties of the new observation method.

  18. Fused rock from Köfels, Tyrol

    USGS Publications Warehouse

    Milton, Daniel J.

    1964-01-01

    The vesicular glass from Köfels, Tyrol, contains grains of quartz that have been partially melted but not dissolved in the matrix glass. This phenomenon has been observed in similar glasses formed by friction along a thrust fault and by meteorite impact, but not in volcanic glasses. The explosion of a small nuclear device buried behind a steep slope produced a geologic structure that is a good small-scale model of that at Köfels. Impact of a large meteorite would have an effect analogous to that of a subsurface nuclear explosion and is the probable cause of the Köfels feature.

  19. Enhancing FEL Power with Phase Shifters

    SciTech Connect

    Ratner, Daniel; Chao, Alex; Huang, Zhirong; /SLAC

    2010-07-30

    Tapering the undulator parameter is a well-known method for maintaining the resonant condition past saturation, and increasing Free Electron Laser (FEL) efficiency. In this paper, we demonstrate that shifting the electron bunch phase relative to the radiation is equivalent to tapering the undulator parameter. Using discrete phase changes derived from optimized undulator tapers for the Linac Coherent Light Source (LCLS) x-ray FEL, we show that appropriate phase shifts between undulator sections can reproduce the power enhancement of undulator tapers. Phase shifters are relatively easy to implement and operate, and could be used to aid or replace undulator tapers in optimizing FEL performance.

  20. Longevity of optically activated, high gain GaAs photoconductive semiconductor switches

    SciTech Connect

    Loubriel, G.M.; Zutavern, F.J.; Mar, A.

    1997-08-01

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to well over 10 million pulses by reducing the density of carriers at the semiconductor to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The first was achieved by varying the spatial distribution of the trigger light thereby widening the current filaments that are characteristic of the high gain switches. The authors reduced the carrier density in the vertical direction by using ion implantation. These results were obtained for currents of about 10 A, current duration of 3.5 ns, and switched voltage of {approximately}2 kV. At currents of {approximately}70 A, the switches last for 0.6 million pulses. In order to improve the performance at high currents new processes such as deep diffusion and epitaxial growth of contacts are being pursued. To guide this effort the authors measured a carrier density of 6 x 10{sup 18} electrons (or holes)/cm{sup 3} in filaments that carry a current of 5 A.

  1. Suppression of mode-beating in a saturated hole-coupled FEL oscillator

    SciTech Connect

    Krishnagopal, S.; Xie, M.; Kim, K.J.

    1992-08-01

    In a hole-coupled resonator, either empty or loaded with a linear FEL gain medium, the phenomenon of mode-degeneracy and mode-beating have been studied. When the magnitudes of the eigenvalues, derived from a linear analysis, are equal for two or more dominant eigenmodes, the system cannot achieve a stable beam-profile. We investigate this phenomenon when a saturated FEL is present within the cavity, thus introducing non-linearity. We use a three-dimensional FEL oscillator code, based on the amplifier code TDA, and show that mode-beating is completely suppressed in the nonlinear saturated regime. We suggest a simple, qualitative model for the mechanism responsible for this suppression.

  2. Efficient frequency doubler for the soft X-ray SASE FEL at the TESLA Test Facility

    NASA Astrophysics Data System (ADS)

    Feldhaus, J.; Körfer, M.; Möller, T.; Pflüger, J.; Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

    2004-08-01

    This paper describes an effective frequency doubler scheme for SASE free electron lasers (FEL). It consists of an undulator tuned to the first harmonic, a dispersion section, and a tapered undulator tuned to the second harmonic. The first stage is a conventional soft X-ray SASE FEL. Its gain is controlled in such a way that the maximum energy modulation of the electron beam at the exit is about equal to the local energy spread, but still far away from saturation. When the electron bunch passes through the dispersion section this energy modulation leads to effective compression of the particles. Then the bunched electron beam enters the tapered undulator and produces strong radiation in the process of coherent deceleration. We demonstrate a frequency doubler scheme that can be integrated into the SASE FEL at the TESLA Test Facility at DESY, and will allow to reach 3 nm wavelength with GW-level of output peak power. This would extend the operating range of the FEL into the so-called water window and significantly expand the capabilities of the TTF FEL user facility.

  3. Simulation of waveguide FEL oscillator using RF linac

    SciTech Connect

    Kuruma, S.; Asakawa, M.; Imasaki, K.

    1995-12-31

    One dimensional multifrequency simulation code for waveguide mode FEL has been developed. Using this simulation code, we analyzed the spontaneous emission from electron micropulse from RF Linac. It is found that some parameters both high and low frequency waveguide modes are growing simultaneously, so the two radiation pulses are generated and amplified. And the experimental data for cavity length detuning of the radiation power are analyzed.

  4. Polarization beam combination technique for gain saturation effect compensation in high-energy systems

    NASA Astrophysics Data System (ADS)

    Chen, Junchi; Peng, Yujie; Su, Hongpeng; Leng, Yuxin

    2016-06-01

    To compensate for the gain saturation effect in the high-energy laser amplifier, a modified polarization beam combination (PBC) method is introduced to reshape temporal waveform of the injected laser pulse to obtain a controlled high-energy laser pulse shape after amplification. One linearly polarized beam is divided into two orthogonal polarized beams, which spatially recombine together collinearly after propagating different optical paths with relative time delay in PBC structure. The obtained beam with polarization direction being rotated by the following half wave plate is divided and combined again to reform a new beam in another modified polarization beam structure. The reformed beam is injected into three cascaded laser amplifiers. The amplified pulse shape can be controlled by the incident pulse shape and amplifier gain, which is agreeable to the simulation by the Frank-Nodvik equations. Based on the simple method, the various temporal waveform of output pulse with tunable 7 to 20 ns pulse duration can be obtained without interferometric fringes.

  5. Effects of high count rate and gain shift on isotope identification algorithms

    SciTech Connect

    Robinson, Sean M.; Kiff, Scott D.; Ashbaker, Eric D.; Flumerfelt, Eric L.; Salvitti, Matthew

    2009-11-01

    Spectroscopic gamma-ray detectors are used for many research, industrial, and homeland- security applications. Thallium-doped sodium iodide, (NaI(Tl)), scintillation crystals coupled to photomultiplier tubes provide medium-resolution spectral data about the surrounding environment. NaI(Tl)-based detectors, paired with spectral identification algorithms, are often effective for identifying gamma-ray sources by isotope. However, intrinsic limitations for NaI(Tl) systems exist, including gain shifts and spectral marring (e.g., loss of resolution and count-rate saturation) at high count rates. These effects are hardware dependent and have strong effects on the radioisotopic identification capability of NaI(Tl)-based systems. In this work, the effects of high count rate on the response of isotope-identification algorithms are explored. It is shown that a small gain shift of a few tens of keV is sufficient to disturb identification. The onset of this and other spectral effects is estimated for NaI(Tl) crystals, and a mechanism for mitigating these effects by estimating and correcting for them is implemented and evaluated.

  6. Effects of High Count Rate and Gain Shift on Isotope Identification Algorithms

    SciTech Connect

    Robinson, Sean M.; Kiff, Scott D.; Ashbaker, Eric D.; Bender, Sarah E.; Flumerfelt, Eric L.; Salvitti, Matthew; Borgardt, James D.; Woodring, Mitchell L.

    2007-12-31

    Spectroscopic gamma-ray detectors are used for many research applications, as well as Homeland Security screening applications. Sodium iodide (NaI) scintillator crystals coupled with photomultiplier tubes (PMTs) provide medium-resolution spectral data about the surrounding environment. NaI based detectors, paired with spectral identification algorithms, are often effective in identifying sources of interest by isotope. However, intrinsic limitations exist for NaI systems because of gain shifts and spectral marring (e.g., loss of resolution and count-rate saturation) at high count rates. These effects are hardware dependent, and have strong effects on the radioisotopic identification capability of these systems. In this work, the effects of high count rate on the capability of isotope identification algorithms are explored. It is shown that a small gain shift of a few tens of keV is sufficient to disturb identification. The onset of this and other spectral effects are estimated for several systems., and a mechanism for mitigating these effects by estimating and correcting for them is implemented and evaluated.

  7. Longevity improvement of optically activated, high gain GaAs photoconductive semiconductor switches

    SciTech Connect

    MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES; HJALMARSON,HAROLD P.; BACA,ALBERT G.

    2000-03-02

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses at 23A, and over 100 pulses at 1kA. This is achieved by improving the ohmic contacts by doping the semi-insulating GaAs underneath the metal, and by achieving a more uniform distribution of contact wear across the entire switch by distributing the trigger light to form multiple filaments. This paper will compare various approaches to doping the contacts, including ion implantation, thermal diffusion, and epitaxial growth. The device characterization also includes examination of the filament behavior using open-shutter, infra-red imaging during high gain switching. These techniques provide information on the filament carrier densities as well as the influence that the different contact structures and trigger light distributions have on the distribution of the current in the devices. This information is guiding the continuing refinement of contact structures and geometries for further improvements in switch longevity.

  8. Calculation of coherent emissions and gain from a prebunched Free Electron Laser

    SciTech Connect

    Treadwell, E.A. |

    1995-08-01

    This report advances a theoretical model for the single pass growth of coherent radiation in a prebunched FEL system. The FEL system includes a radio frequency linear accelerator (fr linac) as the injector, a resonator cavity with a wiggler magnet, and two highly reflective plano-concave mirrors, typically 99{percent} of the radiation is reflected inside the resonator. The model is based upon the following assumptions: a) the electron beam is cold, b) a super- electron is a particle with {approximately} 10{sup 8} elementary charges inside a bunch; the bunch length is much smaller than the radiation wavelength and the super-electron scatters with the rf wave in a single pass through the resonator, c) a smooth phase space transition must exist between the rf linac and the resonator, d) the energy gain is low per pass and consequently in the linear gain regime, and e) if condition (b) is satisfied and the bunch is resonant with the FEL beat wave, all electrons lose energy to the wave, in the lowest order approximation. A simple scaling technique is used to calculate the output power given the number of particles in a bunch and the efficiency for retrieving coherent radiation from the resonator. 4 refs., 8 figs., 2 tabs.

  9. Redesign of a Variable-Gain Output Feedback Longitudinal Controller Flown on the High-Alpha Research Vehicle (HARV)

    NASA Technical Reports Server (NTRS)

    Ostroff, Aaron J.

    1998-01-01

    This paper describes a redesigned longitudinal controller that flew on the High-Alpha Research Vehicle (HARV) during calendar years (CY) 1995 and 1996. Linear models are developed for both the modified controller and a baseline controller that was flown in CY 1994. The modified controller was developed with three gain sets for flight evaluation, and several linear analysis results are shown comparing the gain sets. A Neal-Smith flying qualities analysis shows that performance for the low- and medium-gain sets is near the level 1 boundary, depending upon the bandwidth assumed, whereas the high-gain set indicates a sensitivity problem. A newly developed high-alpha Bode envelope criterion indicates that the control system gains may be slightly high, even for the low-gain set. A large motion-base simulator in the United Kingdom was used to evaluate the various controllers. Desired performance, which appeared to be satisfactory for flight, was generally met with both the low- and medium-gain sets. Both the high-gain set and the baseline controller were very sensitive, and it was easy to generate pilot-induced oscillation (PIO) in some of the target-tracking maneuvers. Flight target-tracking results varied from level 1 to level 3 and from no sensitivity to PIO. These results were related to pilot technique and whether actuator rate saturation was encountered.

  10. High gain 1.3-μm GaInNAs SOA with fast gain dynamics and enhanced temperature stability

    NASA Astrophysics Data System (ADS)

    Fitsios, D.; Giannoulis, G.; Iliadis, N.; Korpijärvi, V.-M.; Viheriälä, J.; Laakso, A.; Dris, S.; Spyropoulou, M.; Avramopoulos, H.; Kanellos, G. T.; Pleros, N.; Guina, M.

    2014-03-01

    Semiconductor optical amplifiers (SOAs) are a well-established solution of optical access networks. They could prove an enabling technology for DataCom by offering extended range of active optical functionalities. However, in such costand energy-critical applications, high-integration densities increase the operational temperatures and require powerhungry external cooling. Taking a step further towards improving the cost and energy effectiveness of active optical components, we report on the development of a GaInNAs/GaAs (dilute nitride) SOA operating at 1.3μm that exhibits a gain value of 28 dB and combined with excellent temperature stability owing to the large conduction band offset between GaInNAs quantum well and GaAs barrier. Moreover, the characterization results reveal almost no gain variation around the 1320 nm region for a temperature range from 20° to 50° C. The gain recovery time attained values as short as 100 ps, allowing implementation of various signal processing functionalities at 10 Gb/s. The combined parameters are very attractive for application in photonic integrated circuits requiring uncooled operation and thus minimizing power consumption. Moreover, as a result of the insensitivity to heating issues, a higher number of active elements can be integrated on chip-scale circuitry, allowing for higher integration densities and more complex optical on-chip functions. Such component could prove essential for next generation DataCom networks.

  11. Proposed UV FEL user facility at BNL

    NASA Astrophysics Data System (ADS)

    Ben-Zvi, I.; Di Mauro, L. F.; Krinsky, S.; White, M. G.; Yu, L. H.

    1991-07-01

    The NSLS at Brookhaven National Laboratory is proposing the construction of an UV FEL operating in the wavelength range from visible to 1000 Å. Nanocoulomb electron pulses will be generated at a laser photocathode rf gun at a repetition rate of 10 kHz. The 6 ps pulses will be accelerated to 250 MeV in a superconducting linac. The FEL consists of an exponential growth section followed by a tapered section. The amplifier input is a harmonic of a tunable visible laser generated either by nonlinear optical material or the nonlinearity of the FEL itself. The FEL output in 10 -4 bandwidth is 1 mJ per pulse, resulting in an average power of 10 W. The availability of radiation with these characteristics would open up new opportunities in photochemistry, biology and nonlinear optics, as discussed in a recent workshop held at BNL.

  12. Comparison of integrated numerical experiments with accelerator and FEL experiments

    SciTech Connect

    Thode, L.E.; Carlsten, B.E.; Chan, K.C.D.; Cooper, R.K.; Elliott, J.C.; Gitomer, S.J.; Goldstein, J.C.; Jones, M.E.; McVey, B.D.; Schmitt, M.J.; Takeda, H.; Tokar, R.L.; Wang, T.S.; Young, L.M.

    1991-01-01

    Even at the conceptual level the strong coupling between the laser subsystem elements, such as the accelerator, wiggler, optics, and control, greatly complicates the understanding and design of an FEL. Given the requirements for a high-performance FEL, the coupling between the laser subsystems must be included in the design approach. To address the subsystem coupling the concept of an integrated numerical experiment (INEX) has been implemented. Unique features of the INEX approach are consistency and numerical equivalence of experimental diagnostic. The equivalent numerical diagnostics mitigates the major problem of misinterpretation that often occurs when theoretical and experimental data are compared. A complete INEX model has been applied to the 10{mu}m high-extraction-efficiency experiment at Los Alamos and the 0.6-{mu}m Burst Mode experiment at Boeing Aerospace. In addition, various subsets of the INEX model have been compared with a number of other experiments. Overall, the agreement between INEX and the experiments is very good. With the INEX approach, it now appears possible to design high-performance FELS for numerous applications. The first full-scale test of the INEX approach is the Los Alamos HIBAF experiment. The INEX concept, implementation, and validation with experiments are discussed. 28 refs., 13 figs., 1 tab.

  13. Some observations on spin detector response during Galileo high gain antenna deployment

    NASA Technical Reports Server (NTRS)

    Peng, Chia-Yen; Smith, Kenneth S.

    1992-01-01

    This paper summarizes a dynamic analysis conducted in support of the investigation of the anomalous deployment of the Galileo High Gain Antenna on April 11, 1991. The work was focused on modeling the spacecraft spin dynamics to predict and compare the spin detector telemetry during the antenna deployment for possible cause scenarios. The effects of analog and digital low-pass filtering, digitization, and telemetry on the reported spin rate were studied as well. The high frequency phenomena in the spin detector response are masked by the filtering and sampling of the telemetry data. However, the observed spin detector telemetery is consistent with a single rib popping free, and is most likely associated with a rib near the spin detector, or 180 deg opposite.

  14. A Jitter-Mitigating High Gain Antenna Pointing Algorithm for the Solar Dynamics Observatory

    NASA Technical Reports Server (NTRS)

    Bourkland, Kristin L.; Liu, Kuo-Chia; Blaurock, Carl

    2007-01-01

    This paper details a High Gain Antenna (HGA) pointing algorithm which mitigates jitter during the motion of the antennas on the Solar Dynamics Observatory (SDO) spacecraft. SDO has two HGAs which point towards the Earth and send data to a ground station at a high rate. These antennas are required to track the ground station during the spacecraft Inertial and Science modes, which include periods of inertial Sunpointing as well as calibration slews. The HGAs also experience handoff seasons, where the antennas trade off between pointing at the ground station and pointing away from the Earth. The science instruments on SDO require fine Sun pointing and have a very low jitter tolerance. Analysis showed that the nominal tracking and slewing motions of the antennas cause enough jitter to exceed the HGA portion of the jitter budget. The HGA pointing control algorithm was expanded from its original form as a means to mitigate the jitter.

  15. Millimeter-wave double-dipole antennas for high-gain integrated reflector illumination

    NASA Technical Reports Server (NTRS)

    Filipovic, Daniel F.; Ali-Ahmad, Walid Y.; Rebeiz, Gabriel M.

    1992-01-01

    A double-dipole antenna backed by a ground plane has been fabricated for submillimeter wavelengths. The double-dipole antenna is integrated on a thin dielectric membrane with a planar detector at its center. Measured feed patterns at 246 GHz agree well with theory and demonstrate a rotationally symmetric pattern with high coupling efficiency to Gaussian beams. The input impedance is around 50 ohms, and will match well to a Schottky diode or SIS detector. The double-dipole antenna served as the feed for a small machined parabolic reflector. The integrated reflector had a measured gain of 37 dB at 119 microns. This makes the double-dipole antenna ideally suited as a feed for high resolution tracking or for long focal length Cassegrain antenna systems.

  16. Temporal characteristics of a SASE FEL.

    SciTech Connect

    Li, Y,; Huang, Z.; Kim, K.-J.; Lewellen, J.; Milton, S. V.; Sajaev, V.

    2003-01-01

    We have performed a single-shot, time-resolved measurement of the output field of a SASE FEL using the frequency-resolved optical gating (FROG) technique. The measurement reveals the phase and the amplitude of the SASE output as functions of time and frequency, hence enables us to perform a full characterization of the SASE FEL output. We examined both the single-shot field evolution as well as the statistics over multiple shots on the phase and intensity evolution.

  17. Locking Lasers to RF in an Ultra Fast FEL

    SciTech Connect

    Wilcox, R.; Huang, G.; Doolittle, L.; White, W.; Frisch, J.; Coffee, R.

    2010-01-02

    Using a novel, phase-stabilized RF-over-fiber scheme, they transmit 3GHz over 300m with 27fs RMS error in 250kHz bandwidth over 12 hours, and phase lock a laser to enable ultrafast pump-probe experiments. Free-electron lasers (FELs) are capable of producing short-duration (< 10fs), high-energy X-ray pulses for a range of scientific applications. The recently activated Linac Coherent Light Source (LCLS) FEL facility at SLAC will support experiments which require synchronized light pulses for pump-probe schemes. They developed and operated a fiber optic RF transmission system to synchronize lasers to the emitted X-ray pulses, which was used to enable the first pump-probe experiments at the LCLS.

  18. A wiggler magnet for FEL low voltage operation

    SciTech Connect

    Al-Shamma`a, A.; Stuart, R.A.; Lucas, J.

    1995-12-31

    In low voltage FELs (ie, 200kV), operation is necessarily in the microwave frequency range for wiggler periods of the order of cms., so that a waveguide system is mandatory. Also, because of the relatively low velocity of the electron beam, the wiggle amplitude of the electron beam can be much larger than is normal for highly relativistic FELs. Both these factors mean that the electron trajectory must be carefully controlled to avoid beam collision with the waveguide walls. A wiggler system with half poles at entrance and exit is not an acceptable solution because of the offset is gives rise to the electron trajectory. Consequently, we have designed and constructed a wiggler magnet with exponential entrance and exit tapers for a minimal deflection and displacement of the electron beam. Simulations and experimental measurements showed that an on axis trajectory is easily obtainable.

  19. Technological Challenges to X-Ray FELs

    SciTech Connect

    Nuhn, Heinz-Dieter

    1999-09-16

    There is strong interest in the development of x-ray free electron lasers (x-ray FELs). The interest is driven by the scientific opportunities provided by intense, coherent x-rays. An x-ray FEL has all the characteristics of a fourth-generation source: brightness several orders of magnitude greater than presently achieved in third-generation sources, full transverse coherence, and sub-picosecond long pulses. The SLAC and DESY laboratories have presented detailed design studies for X-Ray FEL user facilities around the 0.1 nm wavelength-regime (LCLS at SLAC, TESLA X-Ray FEL at DESY). Both laboratories are engaged in proof-of-principle experiments are longer wavelengths (TTF FEL Phase I at 71 nm, VISA at 600-800 nm) with results expected in 1999. The technologies needed to achieve the proposed performances are those of bright electron sources, of acceleration systems capable of preserving the brightness of the source, and of undulators capable of meeting the magnetic and mechanical tolerances that are required for operation in the SASE mode. This paper discusses the technological challenges presented by the X-Ray FEL projects.

  20. Technological challenges to X-ray FELs

    NASA Astrophysics Data System (ADS)

    Nuhn, Heinz-Dieter

    2000-05-01

    There is strong interest in the development of X-ray Free Electron Lasers (X-ray FELs). The interest is driven by the scientific opportunities provided by intense, coherent X-rays. An X-ray FEL has all the characteristics of a fourth-generation source: brightness several orders of magnitude greater than presently achieved in third-generation sources, full transverse coherence, and sub-picosecond long pulses. The SLAC and DESY laboratories have presented detailed design studies for X-ray FEL user-facilities around the 0.1 nm wavelength regime (LCLS at SLAC, TESLA X-ray FEL at DESY). Both laboratories are engaged in proof-of-principle experiments at longer wavelengths (TTF FEL Phase I at 71 nm, VISA at 600-800 nm) with results expected in 1999. The technologies needed to achieve the proposed performances are those of bright electron sources, of acceleration systems capable of preserving the brightness of the source, and of undulators capable of meeting the magnetic and mechanical tolerances that are required for operation in the SASE mode. This paper discusses the technological challenges presented by the X-ray FEL projects.

  1. Progress in laboratory high gain ICF (inertial confinement fusion): Prospects for the future

    SciTech Connect

    Storm, E.; Lindl, J.D.; Campbell, E.M.; Bernat, T.P.; Coleman, L.W.; Emmett, J.L.; Hogan, W.J.; Hunt, J.T.; Krupke, W.F.; Lowdermilk, W.H.

    1988-01-01

    Inertial confinement fusion (ICF), a thermonuclear reaction in a small (/approximately/5 mm diameter) fuel capsule filled with a few milligrams of deuterium and tritium, has been the subject of very fruitful experimentation since the early 1970's. High gain ICF is now on the threshold of practical applications. With a Laboratory Microfusion Facility (LMF), these applications will have major implications for national defense, basic and applied science, and power production. With a driver capable of delivering about 10 MJ in a 10-ns pulse at an intensity of /approximately/3 /times/ 10/sup 14/ W/cm/sup 2/, an appropriately configured cryogenic capsule could be compressed to a density of about 200 g/cm/sup 3/ and a temperature of 3--5 keV. Under these conditions, up to 10 mg of DT could be ignited, and with a burn efficiency of about 30%, release up to 1000 MJ of fusion energy, an energy gain of about 100. A thousand megajoules is equivalent to about one quarter ton of TNT, or about 7 gallons of oil--an amount of energy tractable under laboratory conditions and potentially very useful for a variety of applications. 61 refs., 33 figs.

  2. Feasibility studies of a compact mm-wave linac FEL

    SciTech Connect

    Nassiri, A.; Kustom, R.L.; Kang, Y.W.; Song, J.

    1995-12-31

    Short wavelength FELs impose stringent requirements on the quality of the electron beams. The key factor in obtaining a single-pass UV or x-ray FEL is the generation of small emittance electron beams with ultra-high brightness. The pioneering work at Los Alamos National Laboratory in the last decade has resulted in a dramatic improvement in the production of high electron beam brightness and small beam emittance using rf photocathode gun. The lower bound on the emittance of a 1-nC bunch without any emittance compensation is on the order of 3 {pi} mm-mrad. This is well within the emittance requirement being considered here. Although the original R&D work at Argonne, in collaboration with the University of Illinois at Chicago and University of Wisconsin-Madison, has produced encouraging results in the area of rf structure design, x-ray mask fabrication, and LIGA processing (Lithography, Electroforming, and Molding), the goal to prove feasibility has not yet been achieved. In this paper, we will present feasibility studies for a compact single-pass mm-linac FEL based on LIGA technology. This system will consist of a photocathode rf gun operated at 30 GHz, a 50-MeV superconducting constant gradient structure operated at 60 GHz, and a microundulator with 1-mm period.

  3. Design of a high-power, high-gain, 2nd harmonic, 22.848 GHz gyroklystron

    NASA Astrophysics Data System (ADS)

    Veale, M.; Purohit, P.; Lawson, W.

    2013-08-01

    In this paper we consider the design of a four-cavity, high-gain K-band gyroklystron experiment for high gradient structure testing. The frequency doubling gyroklystron utilizes a beam voltage of 500 kV and a beam current of 200 A from a magnetron injection gun (MIG) originally designed for a lower-frequency device. The microwave circuit features input and gain cavities in the circular TE011 mode and penultimate and output cavities that operate at the second harmonic in the TE021 mode. We investigate the MIG performance and study the behavior of the circuit for different values of perpendicular to parallel velocity ratio (α = V⊥ / Vz). This microwave tube is expected to be able to produce at least 20 MW of power in 1μs pulses at a repetition rate of at least 120 Hz. A maximum efficiency of 26% and a large signal gain of 58 dB under zero-drive stable conditions were simulated for a velocity ratio equal to 1.35.

  4. Design of a high-power, high-gain, 2nd harmonic, 22.848 GHz gyroklystron

    SciTech Connect

    Veale, M.; Purohit, P.; Lawson, W.

    2013-08-15

    In this paper we consider the design of a four-cavity, high-gain K-band gyroklystron experiment for high gradient structure testing. The frequency doubling gyroklystron utilizes a beam voltage of 500 kV and a beam current of 200 A from a magnetron injection gun (MIG) originally designed for a lower-frequency device. The microwave circuit features input and gain cavities in the circular TE{sub 011} mode and penultimate and output cavities that operate at the second harmonic in the TE{sub 021} mode. We investigate the MIG performance and study the behavior of the circuit for different values of perpendicular to parallel velocity ratio (α= V{sub ⊥}/ V{sub z}). This microwave tube is expected to be able to produce at least 20 MW of power in 1μs pulses at a repetition rate of at least 120 Hz. A maximum efficiency of 26% and a large signal gain of 58 dB under zero-drive stable conditions were simulated for a velocity ratio equal to 1.35.

  5. High performance quantum cascade lasers: Loss, beam stability, and gain engineering

    NASA Astrophysics Data System (ADS)

    Bouzi, Pierre Michel

    Quantum Cascade (QC) lasers are semiconductor devices emitting in the mid-infrared (3-30 micron) and terahertz (30-300 micron) regions of the electromagnetic spectrum. Since their first demonstration by Jerome Faist et. al. in 1994, they have evolved very quickly into high performance devices and given rise to many applications such as trace-gas sensing, medical diagnosis, free-space communication, and light detection and ranging (LIDAR). In this thesis, we investigate a further increase of the performance of QC devices and, through meticulous device modeling and characterizations, gain a deeper understanding of several of their unique characteristics, especially their carrier transport and lifetime, their characteristic temperature, their waveguide loss and modal gain, their leakage current, and their transverse mode profile. First, in our quest to achieve higher performance, we investigate the effect of growth asymmetries on device transport characteristics. This investigation stems from recent studies on the role of interface roughness on intersubband scattering and device performance. Through a symmetric active core design, we find that interface roughness and ionized impurity scattering induced by dopant migration play a significant role in carrier transport through the device. Understanding how interface roughness affects intersubband scattering, in turn, we engineer the gain in QC devices by placing monolayer barriers at specific locations within the device band structure. These strategically placed additional thin barrier layers introduce roughness scattering into the device active region, thereby selectively decreasing the lower laser state lifetime and increasing population inversion necessary for laser action. Preliminary measurement results from modified devices reveal a 50% decrease in the emission broadening compared to the control structures, which should lead to a two-fold increase in gain. A special class of so-called "strong coupling" QC lasers

  6. High-gain inverters based on WSe2 complementary field-effect transistors.

    PubMed

    Tosun, Mahmut; Chuang, Steven; Fang, Hui; Sachid, Angada B; Hettick, Mark; Lin, Yongjing; Zeng, Yuping; Javey, Ali

    2014-05-27

    In this work, the operation of n- and p-type field-effect transistors (FETs) on the same WSe2 flake is realized,and a complementary logic inverter is demonstrated. The p-FET is fabricated by contacting WSe2 with a high work function metal, Pt, which facilities hole injection at the source contact. The n-FET is realized by utilizing selective surface charge transfer doping with potassium to form degenerately doped n+ contacts for electron injection. An ON/OFF current ratio of >10(4) is achieved for both n- and p-FETs with similar ON current densities. A dc voltage gain of >12 is measured for the complementary WSe2 inverter. This work presents an important advance toward realization of complementary logic devices based on layered chalcogenide semiconductors for electronic applications. PMID:24684575

  7. NASA/Cousteau ocean bathymetry experiment. Remote bathymetry using high gain LANDSAT data

    NASA Technical Reports Server (NTRS)

    Polcyn, F. C.

    1976-01-01

    Satellite remote bathymetry was varified to 22 m depths where water clarity was defined by alpha = .058 1/m and bottom reflection, r(b), was 26%. High gain band 4 and band 5 CCT data from LANDSAT 1 was used for a test site in the Bahama Islands and near Florida. Near Florida where alpha = .11 1/m and r(b) = 20%, depths to 10 m were verified. Depth accuracies within 10% rms were achieved. Position accuracies within one LANDSAT pixel were obtained by reference to the Transit navigation satellites. The Calypso and the Beayondan, two ships, were at anchor on each of the seven days during LANDSAT 1 and 2 overpasses: LORAN C position information was used when the ships were underway making depth transects. Results are expected to be useful for updating charts showing shoals hazardous to navigation or in monitoring changes in nearshore topography.

  8. Suppression of higher mode excitation in a high gain relativistic klystron amplifier

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Xu, Z.; Jin, X.; Li, Z. H.; Tang, C. X.

    2012-02-01

    Suppressing higher mode excitation is very important in the high gain relativistic klystron amplifier because higher mode can seriously degrade klystron performance and cause pulse shortening. The mechanism of higher mode self-excitation is explored in the PIC simulation, and it is shown the coupling between cavities is the main cause of higher mode self-excitation. The coupling forms the positive feedback loop for higher mode to be excited just like that in the oscillator circuit. The formula for startup current of higher mode self-excitation is developed based on the coupling between cavities. And the corresponding methods are taken to avoid higher mode self-excitation. Finally, mode control is realized in the RKA with output power up to 1.02 GW when driven power is only few kilowatts.

  9. Calibration of Gimbaled Platforms: The Solar Dynamics Observatory High Gain Antennas

    NASA Technical Reports Server (NTRS)

    Hashmall, Joseph A.

    2006-01-01

    Simple parameterization of gimbaled platform pointing produces a complete set of 13 calibration parameters-9 misalignment angles, 2 scale factors and 2 biases. By modifying the parameter representation, redundancy can be eliminated and a minimum set of 9 independent parameters defined. These consist of 5 misalignment angles, 2 scale factors, and 2 biases. Of these, only 4 misalignment angles and 2 biases are significant for the Solar Dynamics Observatory (SDO) High Gain Antennas (HGAs). An algorithm to determine these parameters after launch has been developed and tested with simulated SDO data. The algorithm consists of a direct minimization of the root-sum-square of the differences between expected power and measured power. The results show that sufficient parameter accuracy can be attained even when time-dependent thermal distortions are present, if measurements from a pattern of intentional offset pointing positions is included.

  10. Image-Guided Radio-Frequency Gain Calibration for High-Field MRI

    PubMed Central

    Breton, Elodie; McGorty, KellyAnne; Wiggins, Graham C.; Axel, Leon; Kim, Daniel

    2010-01-01

    High-field (≥ 3T) MRI provides a means to increase the signal-to-noise ratio, due to its higher tissue magnetization compared with 1.5T. However, both the static magnetic field (B0) and the transmit radio-frequency (RF) field (B1+) inhomogeneities are comparatively higher than those at 1.5T. These challenging factors at high-field strengths make it more difficult to accurately calibrate the transmit RF gain using standard RF calibration procedures. An image-based RF calibration procedure was therefore developed, in order to accurately calibrate the transmit RF gain within a specific region-of-interest (ROI). Using a single-shot ultra-fast gradient echo pulse sequence with centric k-space reordering, a series of “saturation-no-recovery” images was acquired by varying the flip angle of the preconditioning pulse. In the resulting images, the signal null occurs in regions where the flip angle of the preconditioning pulse is 90°. For a given ROI, the mean signal can be plotted as a function of the nominal flip angle, and the resulting curve can be used to quantitatively identify the signal null. This image-guided RF calibration procedure was evaluated through phantom and volunteer imaging experiments at 3T and 7T. The image-guided RF calibration results in vitro were consistent with standard B0 and B1+ maps. The standard automated RF calibration procedure produced approximately 20% and 15–30% relative error in the transmit RF gain in the left kidney at 3T and brain at 7T, respectively. For initial application, a T2 mapping pulse sequence was applied at 7T. The T2 measurements in the thalamus at 7T were 60.6 ms and 48.2 ms using the standard and image-guided RF calibration procedures, respectively. This rapid, image-guided RF calibration procedure can be used to optimally calibrate the flip angle for a given ROI and thus minimize measurement errors for quantitative MRI and MR spectroscopy. PMID:20014333

  11. Space charge field in a FEL with axially symmetric electron beam

    SciTech Connect

    Goncharov, I.A.; Belyavskiy, E.D.

    1995-12-31

    Nonlinear two-dimensional theory of the space charge of an axially symmetric electron beam propagating in combined right-hand polarized wiggler and uniform axial guide fields in a presence of high-frequency electromagnetic wave is presented. The well-known TE{sub 01} mode in a cylindrical waveguide for the model of radiation fields and paraxial approximation for the wiggler field are used. Space charge field components are written in the Lagrange coordinates by the twice averaged Green`s functions of two equally charged infinitely thin discs. For that {open_quotes}compensating charges{close_quotes} method is applied in which an electron ring model is substituted by one with two different radii and signs discs. On this approach the initial Green`s functions peculiarities are eliminated and all calculations are considerably simplified. Coefficients of a twice averaged Green`s function expansion into a Fourier series are obtained by use of corresponding expansion coefficients of longitudinal Green`s functions of equal radii discs and identical rings known from the one-dimensional theory of super HF devices taking into account electron bunches periodicity. This approach permit the space charge field components for an arbitrary stratified stream to be expressed in a simple and strict enough form. The expressions obtained can be employed in a nonlinear two-dimensional FEL theory in order to investigate beam dynamical defocusing and electrons failing on the waveguide walls in the high gain regime. This is especially important for FEL operation in mm and submm.

  12. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae)

    PubMed Central

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A.; Sterck, Frank; Strijk, Joeri S.; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems. PMID:26461108

  13. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae).

    PubMed

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A; Sterck, Frank; Strijk, Joeri S; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems. PMID:26461108

  14. Nanoparticle-assisted high photoconductive gain in polymer/fullerene matrix

    PubMed Central

    Chen, Hsiang-Yu; Lo, Michael K. F.; Yang, Guanwen; Monbouquette, Harold G.; Yang, Yang

    2014-01-01

    Polymer/inorganic nanocrystal composites1–10 offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by the solubility11 and distribution of nanocrystals (NCs) in polymer matrices. Here, a high photoconductive gain has been achieved by blending cadmium telluride (CdTe) nanoparticles (NPs) into a polymer/fullerene matrix followed by a solvent annealing12 process. The NP surface capping ligand, N-phenyl-N’-methyldithiocarbamate, renders the NPs highly soluble in the polymer blend thereby enabling high nanocrystal loadings. An external quantum efficiency (EQE) as high as ~8000% (at 350nm) is reached at −4.5V. Hole-dominant devices coupled with AFM images are studied to uncover the probable mechanism. We observe a higher concentration of CdTe NPs is located near the cathode/polymer interface. These NPs with trapped electrons assist hole injection into the polymer under reverse bias, which contributes to greater than 100% EQE. PMID:18772915

  15. Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

    NASA Astrophysics Data System (ADS)

    Kazlauskas, Karolis; Kreiza, Gediminas; Bobrovas, Olegas; AdomÄ--nienÄ--, Ona; AdomÄ--nas, Povilas; Jankauskas, Vygintas; JuršÄ--nas, Saulius

    2015-07-01

    Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10-2 cm2/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 109 s-1) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm2) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm-1) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

  16. Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

    SciTech Connect

    Kazlauskas, Karolis Kreiza, Gediminas; Bobrovas, Olegas; Adomėnienė, Ona; Adomėnas, Povilas; Juršėnas, Saulius; Jankauskas, Vygintas

    2015-07-27

    Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10{sup −2} cm{sup 2}/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 10{sup 9 }s{sup −1}) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm{sup 2}) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm{sup −1}) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

  17. All AlGaN epitaxial structure solar-blind avalanche photodiodes with high efficiency and high gain

    NASA Astrophysics Data System (ADS)

    Wu, Hualong; Wu, Weicong; Zhang, Hongxian; Chen, Yingda; Wu, Zhisheng; Wang, Gang; Jiang, Hao

    2016-05-01

    Solar-blind avalanche photodiodes were fabricated with an all AlGaN-based epitaxial structure on sapphire by metal–organic chemical vapor deposition. The devices demonstrate a maximum responsivity of 114.1 mA/W at 278 nm and zero bias, corresponding to an external quantum efficiency (EQE) of 52.7%. The EQE improves to 64.8% under a bias of ‑10 V. Avalanche gain higher than 2 × 104 was obtained at a bias of ‑140 V. The high performance is attributed to the all AlGaN-based p–i–n structure comprised of undoped and Si-doped n-type Al0.4Ga0.6N on a high quality AlN layer and highly conductive p-type AlGaN grown with In-surfactant-assisted Mg-delta doping.

  18. Normal Visual Acuity and Electrophysiological Contrast Gain in Adults with High-Functioning Autism Spectrum Disorder.

    PubMed

    Tebartz van Elst, Ludger; Bach, Michael; Blessing, Julia; Riedel, Andreas; Bubl, Emanuel

    2015-01-01

    A common neurodevelopmental disorder, autism spectrum disorder (ASD), is defined by specific patterns in social perception, social competence, communication, highly circumscribed interests, and a strong subjective need for behavioral routines. Furthermore, distinctive features of visual perception, such as markedly reduced eye contact and a tendency to focus more on small, visual items than on holistic perception, have long been recognized as typical ASD characteristics. Recent debate in the scientific community discusses whether the physiology of low-level visual perception might explain such higher visual abnormalities. While reports of this enhanced, "eagle-like" visual acuity contained methodological errors and could not be substantiated, several authors have reported alterations in even earlier stages of visual processing, such as contrast perception and motion perception at the occipital cortex level. Therefore, in this project, we have investigated the electrophysiology of very early visual processing by analyzing the pattern electroretinogram-based contrast gain, the background noise amplitude, and the psychophysical visual acuities of participants with high-functioning ASD and controls with equal education. Based on earlier findings, we hypothesized that alterations in early vision would be present in ASD participants. This study included 33 individuals with ASD (11 female) and 33 control individuals (12 female). The groups were matched in terms of age, gender, and education level. We found no evidence of altered electrophysiological retinal contrast processing or psychophysical measured visual acuities. There appears to be no evidence for abnormalities in retinal visual processing in ASD patients, at least with respect to contrast detection. PMID:26379525

  19. Transportation-cyber-physical-systems-oriented engine cylinder pressure estimation using high gain observer

    NASA Astrophysics Data System (ADS)

    Li, Yong-Fu; Xiao-Pei, Kou; Zheng, Tai-Xiong; Li, Yin-Guo

    2015-05-01

    In transportation cyber-physical-systems (T-CPS), vehicle-to-vehicle (V2V) communications play an important role in the coordination between individual vehicles as well as between vehicles and the roadside infrastructures, and engine cylinder pressure is significant for engine diagnosis on-line and torque control within the information exchange process under V2V communications. However, the parametric uncertainties caused from measurement noise in T-CPS lead to the dynamic performance deterioration of the engine cylinder pressure estimation. Considering the high accuracy requirement under V2V communications, a high gain observer based on the engine dynamic model is designed to improve the accuracy of pressure estimation. Then, the analyses about convergence, converge speed and stability of the corresponding error model are conducted using the Laplace and Lyapunov method. Finally, results from combination of Simulink with GT-Power based numerical experiments and comparisons demonstrate the effectiveness of the proposed approach with respect to robustness and accuracy. Project supported by the National Natural Science Foundation of China (Grant No. 61304197), the Scientific and Technological Talents of Chongqing, China (Grant No. cstc2014kjrc-qnrc30002), the Key Project of Application and Development of Chongqing, China (Grant No. cstc2014yykfB40001), the Natural Science Funds of Chongqing, China (Grant No. cstc2014jcyjA60003), and the Doctoral Start-up Funds of Chongqing University of Posts and Telecommunications, China (Grant No. A2012-26).

  20. Characterization of a high-gain Ne-like Fe transient x-ray laser

    SciTech Connect

    Dunn, J; Facnov, A; Fournier, K B; Moon, S J; Osterheld, A; Pikuz, T; Shlyaptsev, V N

    1999-09-13

    The authors present experimental results of a high efficiency Ne-like Fe transient collisional excitation x-ray laser using the COMET 15 TW table-top laser system at LLNL. The plasma formation, ionization and collision excitation of the x-ray laser have been optimized using two sequential laser pulses: a plasma formation beam with 5 J energy of 600 ps duration and a pump beam with 5 J energy of 1.2 ps duration. Since the observation of strong lasing on the 255 {angstrom} 3p-3s J = 0-1 transition of Ne-like Fe, they have achieved high gains of 35 cm{sup {minus}1} and saturation of the x-ray laser. A five-stage traveling wave excitation enhances the strongest Fe 3p-3s 255 {angstrom} lasing line as well as additional x-ray lines. A careful characterization of the plasma column conditions using L-shell spectroscopy indicates the degree of ionization along the line focus.

  1. Normal Visual Acuity and Electrophysiological Contrast Gain in Adults with High-Functioning Autism Spectrum Disorder

    PubMed Central

    Tebartz van Elst, Ludger; Bach, Michael; Blessing, Julia; Riedel, Andreas; Bubl, Emanuel

    2015-01-01

    A common neurodevelopmental disorder, autism spectrum disorder (ASD), is defined by specific patterns in social perception, social competence, communication, highly circumscribed interests, and a strong subjective need for behavioral routines. Furthermore, distinctive features of visual perception, such as markedly reduced eye contact and a tendency to focus more on small, visual items than on holistic perception, have long been recognized as typical ASD characteristics. Recent debate in the scientific community discusses whether the physiology of low-level visual perception might explain such higher visual abnormalities. While reports of this enhanced, “eagle-like” visual acuity contained methodological errors and could not be substantiated, several authors have reported alterations in even earlier stages of visual processing, such as contrast perception and motion perception at the occipital cortex level. Therefore, in this project, we have investigated the electrophysiology of very early visual processing by analyzing the pattern electroretinogram-based contrast gain, the background noise amplitude, and the psychophysical visual acuities of participants with high-functioning ASD and controls with equal education. Based on earlier findings, we hypothesized that alterations in early vision would be present in ASD participants. This study included 33 individuals with ASD (11 female) and 33 control individuals (12 female). The groups were matched in terms of age, gender, and education level. We found no evidence of altered electrophysiological retinal contrast processing or psychophysical measured visual acuities. There appears to be no evidence for abnormalities in retinal visual processing in ASD patients, at least with respect to contrast detection. PMID:26379525

  2. Germinated Waxy Black Rice Suppresses Weight Gain in High-Fat Diet-Induced Obese Mice.

    PubMed

    Lim, Won-Chul; Ho, Jin-Nyoung; Lee, Hee-Seop; Cho, Hong-Yon

    2016-04-01

    This study was performed to investigate the antiobesity effect of germinated waxy black rice (GWBR) in high-fat diet (HFD)-induced obese mice. The mice were divided into a normal diet (ND) group, HFD group, and 2 test groups for 8 weeks: 2.5% GWBR-supplemented (GWBR-2.5) group and 5% GWBR-supplemented (GWBR-5) group. Supplementing with GWBR significantly reduced body weight gain and lipid accumulation in the liver and adipose tissue compared to the HFD control group. Triglyceride (TG), total cholesterol, and low-density lipoprotein-cholesterol levels in serum were decreased by GWBR supplementation, whereas high-density lipoprotein-cholesterol level significantly increased. In addition, mRNA levels of transcriptional factors, such as peroxisome proliferator-activated receptor-γ, CCAAT enhancer-binding protein (C/EBP)-α, C/EBP-β, sterol regulatory element-binding protein-1c, and related genes, including adipocyte fatty acid-binding protein, fatty acid synthase, and lipoprotein lipase, were significantly lower in the GWBR groups. However, lipolytic enzymes, such as hormone-sensitive lipase, adipose TG lipase, and carnitine palmitoyltransferase-1, and uncoupling protein 2 mRNA levels were significantly higher in GWBR-supplemented mice. These results suggest that GWBR exerts antiobesity effects by decreasing lipid accumulation and promoting lipolysis in HFD-induced obese mice. PMID:27022689

  3. A novel 4H-SiC lateral bipolar junction transistor structure with high voltage and high current gain

    NASA Astrophysics Data System (ADS)

    Deng, Yong-Hui; Xie, Gang; Wang, Tao; Sheng, Kuang

    2013-09-01

    In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor (LBJT) with a base field plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 μm and base doping of 3 × 1017 cm-3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 μm. Besides, an investigation of a 4H-SiC vertical BJT (VBJT) with comparable breakdown voltage (3357 V) shows that the minimum base width of 0.25 μm and base doping as high as 8 × 1017 cm-3 contribute to a maximum current gain of only 128.

  4. Studies of relative gain and timing response of fine-mesh photomultiplier tubes in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Sulkosky, V.; Allison, L.; Barber, C.; Cao, T.; Ilieva, Y.; Jin, K.; Kalicy, G.; Park, K.; Ton, N.; Zheng, X.

    2016-08-01

    We investigated the use of Hamamatsu fine-mesh photomultiplier tube assemblies H6152-70 and H6614-70 with regard to their gain and timing resolution in magnetic fields up to 1.9 T. Our results show that the H6614-70 assembly can operate reliably in magnetic fields exceeding 1.5 T, while preserving a reasonable timing resolution even with a gain reduction of a factor of ≈100. The reduction of the relative gain of the H6152-70 is similar to the H6614-70's near 1.5 T, but its timing resolution worsens considerably at this high field.

  5. A local theory of effect of beam pre-modulation on gain and efficiency in a surface wave pumped free electron laser

    NASA Astrophysics Data System (ADS)

    Sharma, Jyotsna; Sharma, Suresh C.; Bhasin, Anuradha; Jain, V. K.

    2014-08-01

    A pre-modulated relativistic electron beam (REB) counter propagating to the surface wave in the vacuum region Compton backscatters the surface wave into a high frequency radiation. The surface wave extends into the vacuum region and can be employed as a wiggler for the generation of sub-millimeter waves. The growth rate and gain were evaluated for a typical FEL (Free Electron Laser) parameters and It is found that the growth rate and gain of the surface wave pumped free electron laser increases with the modulation index. Moreover, the growth rate of the FEL (Free electron Laser) instability scales as one-third power of the beam density in the Compton regime.

  6. An induction linac developed for FEL application

    NASA Astrophysics Data System (ADS)

    de Mascureau, J.; Anthouard, Ph.; Bardy, J.; Eyharts, Ph.; Eyl, P.; Launspach, J.; Thevenot, M.; Villate, D.

    1992-07-01

    An induction linac is being studied and built at CESTA for FEL application. At first we studied the induction technology and namely the high-voltage (HV) generators and the induction cells. A HV generator designed to feed the cells with calibrated pulses (150 kV, 50 ns, δV/V < 1%) has been built using a resonant charging system and magnetic switches. This generator is planned for kHz repetition-rate operation. A prototype induction cell has also been built and tested with a cable generator. An electron injector (1.5 MeV, 1.5kA) has been designed and is now under test: it uses ten induction cells and a thermionic dispenser cathode. Numerical codes have been developed and simulations have been compared with experimental results for HV generators, induction cells, and the injector. An induction accelerating module has been studied and we plan to have the accelerator working at 3 MeV in 1992.

  7. Lean rats gained more body weight than obese ones from a high-fibre diet.

    PubMed

    Li, Shaoting; Zhang, Cheng; Gu, Yingyi; Chen, Long; Ou, Shiyi; Wang, Yong; Peng, Xichun

    2015-10-28

    There is controversy over previous findings that a high ratio of Firmicutes to Bacteriodetes helps obese animals harvest energy from the diet. To further investigate the relationship between microbial composition and energy harvest, microbial adaptation to diet and time should be considered. In this study, lean and obese rats were successfully induced with low-fat and high-fat diets. An 8-week high soyabean fibre (HSF)-containing diet was then fed to investigate the interaction between the diet and the rats' gut microbiota, as well as their influence on rats' growth. Rats' body weight (BW) was recorded weekly; their plasma lipids and their gut microbiota at week 11, 15 and 19 were analysed. After the consumption of the HSF diet, BW of lean rats increased significantly (P<0·05), but no significant alteration in BW was found in obese rats. The average content of plasma cholesterol was lowered and that of TAG was upgraded in both the groups when fed the HSF diet. There was no significant difference observed at each period between lean and obese rats. In the group of lean rats, the diversity of gut microbiota was elevated strongly (P<0·01), and bacteria from phylum Firmicutes and Bacteroidetes were both increased largely (P<0·01); however, the bacterial diversity and composition in obese rats were less altered after the HSF diet control. In conclusion, the increased Firmicutes and Bacteriodetes might relate to lean rats' higher BW gain; 'obese microbiota' could not help the hosts harvest more energy from the HSF diet. PMID:26316354

  8. Photon Beam Diagnostics for VISA FEL

    SciTech Connect

    Murokh, A.; Pellegrini, C.; Rosenzweig, J.; Frigola, P.; Musumeci, P.; Tremaine, A.; Babzien, M.; Ben-Zvi, I.; Doyuran, A.; Johnson, E.; Skaritka, J.; Wang, X.J.; Van Bibber, K.; Hill, J.M.; LeSage, G.P.; Nguyen, D.; Cornacchia, M.

    1999-11-05

    The VISA (Visible to Infrared SASE Amplifier) project is designed to be a SASE-FEL driven to saturation in the sub-micron wavelength region. Its goal is to test various aspects of the existing theory of Self-Amplified Spontaneous Emission, as well as numerical codes. Measurements include: angular and spectral distribution of the FEL light at the exit and inside of the undulator; electron beam micro-bunching using CTR; single-shot time resolved measurements of the pulse profile, using auto-correlation technique and FROG algorithm. The diagnostics are designed to provide maximum information on the physics of the SASE-FEL process, to ensure a close comparison of the experimental results with theory and simulations.

  9. A Modified Lunar Reconnaissance Orbiter (LRO) High Gain Antenna (HGA) Controller Based on Flight Performance

    NASA Technical Reports Server (NTRS)

    Shah, Neerav

    2010-01-01

    The National Aeronautics and Space Administration's (NASA) Lunar Reconnaissance Orbiter (LRO) was launched on June 18, 2009 and is currently in a 50 km mean altitude polar orbit around the Moon. LRO was designed and built by the NASA Goddard Space Flight Center in Greenbelt, MD. The spacecraft is three-axis stabilized via the attitude control system (ACS), which is composed of various control modes using different sets of sensors and actuators. In addition to pointing the spacecraft, the ACS is responsible for pointing LRO s two appendages, the Solar Array (SA) and the High Gain Antenna (HGA). This study reviews LRO s HGA control system. Starting with an overview of the HGA system, the paper delves into the single input single output (SISO) linear analysis followed by the controller design. Based on flight results, an alternate control scheme is devised to address inherent features in the flight control system. The modified control scheme couples the HGA loop with the spacecraft pointing control loop, and through analysis is shown to be stable and improve transient performance. Although proposed, the LRO project decided against implementing this modification.

  10. Microsecond gain-switched master oscillator power amplifier (1958 nm) with high pulse energy

    SciTech Connect

    Ke Yin; Weiqiang Yang; Bin Zhang; Ying Li; Jing Hou

    2014-02-28

    An all-fibre master oscillator power amplifier (MOPA) emitting high-energy pulses at 1958 nm is presented. The seed laser is a microsecond gain-switched thulium-doped fibre laser (TDFL) pumped with a commercial 1550-nm pulsed fibre laser. The TDFL operates at a repetition rate f in the range of 10 to 100 kHz. The two-stage thulium-doped fibre amplifier is built to scale the energy of the pulses generated by the seed laser. The maximum output pulse energy higher than 0.5 mJ at 10 kHz is achieved which is comparable with the theoretical maximum extractable pulse energy. The slope efficiency of the second stage amplifier with respect to the pump power is 30.4% at f = 10 kHz. The wavelength of the output pulse laser is centred near 1958 nm at a spectral width of 0.25 nm after amplification. Neither nonlinear effects nor significant amplified spontaneous emission (ASE) is observed in the amplification experiments. (lasers)

  11. Spacecraft Angular Rates Estimation with Gyrowheel Based on Extended High Gain Observer

    PubMed Central

    Liu, Xiaokun; Yao, Yu; Ma, Kemao; Zhao, Hui; He, Fenghua

    2016-01-01

    A gyrowheel (GW) is a kind of electronic electric-mechanical servo system, which can be applied to a spacecraft attitude control system (ACS) as both an actuator and a sensor simultaneously. In order to solve the problem of two-dimensional spacecraft angular rate sensing as a GW outputting three-dimensional control torque, this paper proposed a method of an extended high gain observer (EHGO) with the derived GW mathematical model to implement the spacecraft angular rate estimation when the GW rotor is working at large angles. For this purpose, the GW dynamic equation is firstly derived with the second kind Lagrange method, and the relationship between the measurable and unmeasurable variables is built. Then, the EHGO is designed to estimate and calculate spacecraft angular rates with the GW, and the stability of the designed EHGO is proven by the Lyapunov function. Moreover, considering the engineering application, the effect of measurement noise in the tilt angle sensors on the estimation accuracy of the EHGO is analyzed. Finally, the numerical simulation is performed to illustrate the validity of the method proposed in this paper. PMID:27089347

  12. Spacecraft Angular Rates Estimation with Gyrowheel Based on Extended High Gain Observer.

    PubMed

    Liu, Xiaokun; Yao, Yu; Ma, Kemao; Zhao, Hui; He, Fenghua

    2016-01-01

    A gyrowheel (GW) is a kind of electronic electric-mechanical servo system, which can be applied to a spacecraft attitude control system (ACS) as both an actuator and a sensor simultaneously. In order to solve the problem of two-dimensional spacecraft angular rate sensing as a GW outputting three-dimensional control torque, this paper proposed a method of an extended high gain observer (EHGO) with the derived GW mathematical model to implement the spacecraft angular rate estimation when the GW rotor is working at large angles. For this purpose, the GW dynamic equation is firstly derived with the second kind Lagrange method, and the relationship between the measurable and unmeasurable variables is built. Then, the EHGO is designed to estimate and calculate spacecraft angular rates with the GW, and the stability of the designed EHGO is proven by the Lyapunov function. Moreover, considering the engineering application, the effect of measurement noise in the tilt angle sensors on the estimation accuracy of the EHGO is analyzed. Finally, the numerical simulation is performed to illustrate the validity of the method proposed in this paper. PMID:27089347

  13. The APS SASE FEL : modeling and code comparison.

    SciTech Connect

    Biedron, S. G.

    1999-04-20

    A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.

  14. Progress towards a high-gain and robust target design for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Henestroza, Enrique; Grant Logan, B.

    2012-07-01

    Recently [E. Henestroza et al., Phys. Plasmas 18, 032702 (2011)], a new inertial-fusion target configuration, the X-target, using one-sided axial illumination has been explored. This class of target uses annular and solid-profile heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an "X." X-targets using all-DT-filled metal cases imploded by three annular ion beams resulted in fuel densities of ˜50 g/cm3 at peak compression, and fusion gains of ˜50, comparable to heavy ion driven hohlraum targets [D. A. Callahan-Miller and M. Tabak, Phys. Plasmas 7, 2083 (2000)]. This paper discusses updated X-target configurations that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT fuel. The updated configurations are capable of assembling higher fuel areal densities ˜2 g/cm2 using two annular beams to implode the target to peak DT densities ˜100 g/cm3, followed by a fast-ignition solid ion beam which heats the high-density fuel to thermonuclear temperatures in ˜200 ps to start the burn propagation, obtaining gains of ˜300. These targets have been modeled using the radiation-hydrodynamics code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] in two- and three- dimensions to study the properties of the implosion as well as the ignition and burn propagation phases. At typical Eulerian mesh resolutions of a few microns, the aluminum-DT interface shows negligible Rayleigh-Taylor (RT) and Richtmyer-Meshkov instability growth; also, the shear flow of the DT fuel as it slides along the metal X-target walls, which drives the RT and Kelvin Helmholtz instabilities, does not have a major effect on the burning rate. An analytic estimate of the RT instability process at the Al-DT interface shows that the aluminum spikes generated during the pusher deceleration phase would not reach the ignition zone in time to affect the burning

  15. Progress towards a high-gain and robust target design for heavy ion fusion

    SciTech Connect

    Henestroza, Enrique; Grant Logan, B.

    2012-07-15

    Recently [E. Henestroza et al., Phys. Plasmas 18, 032702 (2011)], a new inertial-fusion target configuration, the X-target, using one-sided axial illumination has been explored. This class of target uses annular and solid-profile heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an 'X.' X-targets using all-DT-filled metal cases imploded by three annular ion beams resulted in fuel densities of {approx}50 g/cm{sup 3} at peak compression, and fusion gains of {approx}50, comparable to heavy ion driven hohlraum targets [D. A. Callahan-Miller and M. Tabak, Phys. Plasmas 7, 2083 (2000)]. This paper discusses updated X-target configurations that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT fuel. The updated configurations are capable of assembling higher fuel areal densities {approx}2 g/cm{sup 2} using two annular beams to implode the target to peak DT densities {approx}100 g/cm{sup 3}, followed by a fast-ignition solid ion beam which heats the high-density fuel to thermonuclear temperatures in {approx}200 ps to start the burn propagation, obtaining gains of {approx}300. These targets have been modeled using the radiation-hydrodynamics code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] in two- and three- dimensions to study the properties of the implosion as well as the ignition and burn propagation phases. At typical Eulerian mesh resolutions of a few microns, the aluminum-DT interface shows negligible Rayleigh-Taylor (RT) and Richtmyer-Meshkov instability growth; also, the shear flow of the DT fuel as it slides along the metal X-target walls, which drives the RT and Kelvin Helmholtz instabilities, does not have a major effect on the burning rate. An analytic estimate of the RT instability process at the Al-DT interface shows that the aluminum spikes generated during the pusher deceleration phase would not

  16. EXPERIENCE AND PLANS OF THE JLAB FEL FACILITY AS A USER FACILITY

    SciTech Connect

    Michelle D. Shinn

    2007-08-26

    Jefferson Lab's IR Upgrade FEL building was planned from the beginning to be a user facility, and includes an associated 600 m2 area containing seven laboratories. The high average power capability (multikilowatt-level) in the near-infrared (1-3 microns), and many hundreds of watts at longer wavelengths, along with an ultrafast (~ 1 ps) high PRF (10's MHz) temporal structure makes this laser a unique source for both applied and basic research. In addition to the FEL, we have a dedicated laboratory capable of delivering high power (many tens of watts) of broadband THz light. After commissioning the IR Upgrade, we once again began delivering beam to users in 2005. In this presentation, I will give an overview of the FEL facility and its current performance, lessons learned over the last two years, and a synopsis of current and future experiments.

  17. Physical design of FEL injector based on the performance-enhanced EC-ITC RF gun

    NASA Astrophysics Data System (ADS)

    Hu, Tong-Ning; Chen, Qu-Shan; Pei, Yuan-Ji; Li, Ji; Qin, Bin

    2014-01-01

    To meet the requirements of high performance THz-FEL (Free Electron Laser), a compact scheme of FEL injector was proposed. A thermionic cathode was chosen to emit electrons instead of a photo-cathode with its complex structure and high cost. The effective bunch charge was improved to ~200 pC by adopting an enhanced EC-ITC (External Cathode Independently Tunable Cells) RF gun to extract micro-bunches; back bombardment effects were almost eliminated as well. Constant gradient accelerator structures were designed to improve energy to ~14 MeV, while the focusing system was applied for emittance suppressing and bunch state maintenance. The physical design and beam dynamics of the key components for the FEL injector were analyzed. Furthermore, start-to-end simulations with multi-pulses were performed using homemade MATLAB and Parmela. The results show that continual high brightness electron bunches with a low energy spread and emittance could be obtained stably.

  18. Gain media edge treatment to suppress amplified spontaneous emission in a high power laser

    DOEpatents

    Hackel, Lloyd A.; Soules, Thomas F.; Fochs, Scott N.; Rotter, Mark D.; Letts, Stephan A.

    2011-02-22

    A novel method and apparatus for suppressing ASE and/or parasitic oscillation modes in a laser is introduced. By roughening one or more peripheral edges of a solid-state crystal or ceramic laser gain media and by bonding such edges to a predetermined electromagnetic absorbing material arranged adjacent to the entire outer surface of the peripheral edges of the roughened laser gain media, ASE, parasitic oscillation modes and/or residual pump energy can be effectively suppressed.

  19. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  20. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R.D.

    1994-12-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  1. Design and performance of an Automatic Gain Control system for the High Energy X-Ray Timing Experiment

    NASA Technical Reports Server (NTRS)

    Pelling, Michael R.; Rothschild, Richard E.; Macdonald, Daniel R.; Hertel, Robert; Nishiie, Edward

    1991-01-01

    The High Energy X-Ray Timing Experiment (HEXTE), currently under development for the X-Ray Timing Explorer (XTE) mission, employs a closed loop gain control system to attain 0.5 percent stabilization of each of eight-phoswich detector gains. This Automatic Gain Control (AGC) system utilizes a split window discriminator scheme to control the response of each detector pulse height analyzer to gated Am-241 X-ray events at 60 keV. A prototype AGC system has been implemented and tested within the gain perturbation environment expected to be experienced by the HEXTE instrument in flight. The AGC system and test configuration are described. Response, stability and noise characteristics are measured and compared with theoretical predictions. The system is found to be generally suitable for the HEXTE application.

  2. High-gain AlGaAs/GaAs double heterojunction Darlington phototransistors for optical neural networks

    NASA Technical Reports Server (NTRS)

    Kim, Jae H. (Inventor); Lin, Steven H. (Inventor)

    1991-01-01

    High-gain MOCVD-grown (metal-organic chemical vapor deposition) AlGaAs/GaAs/AlGaAs n-p-n double heterojunction bipolar transistors (DHBTs) and Darlington phototransistor pairs are provided for use in optical neural networks and other optoelectronic integrated circuit applications. The reduced base doping level used results in effective blockage of Zn out-diffusion, enabling a current gain of 500, higher than most previously reported values for Zn-diffused-base DHBTs. Darlington phototransitor pairs of this material can achieve a current gain of over 6000, which satisfies the gain requirement for optical neural network designs, which advantageously may employ neurons comprising the Darlington phototransistor pairs in series with a light source.

  3. Multidimensional simulation studies of the SELENE FEL oscillator/buncher followed by a radiator/amplifier output scheme

    SciTech Connect

    Hahn, S.J.; Fawley, W.M.

    1995-02-01

    We analyze and present numerical simulations of the so-called electron output scheme [G. I. Erg et al., 15th Int. FEL Conf., The Hague, The Netherlands, 1993, Book of Abstracts p. 50; Preprint Budker INP 93-75] applied to the SELENE proposal of using a high power FEL to illuminate satellite solar cells. In this scheme, a first stage FEL oscillator bunches the electron beam while a second stage ``radiator`` extracts high power radiation. Our analysis suggests only in the case where the radiator employs a long, tapered undulator will the electron output scheme produce a significant increase in extraction efficiency over what is obtainable from a simple, single-stage oscillator. 1- and 2-D numerical simulations of a 1.7{mu}m FEL employing the electron output scheme show reasonably large bunching fractions ({approximately} 0.3--0.4) at the output of the oscillator stage but only {le}2% extraction efficiency from the radiator stage.

  4. GINGER simulations of short-pulse effects in the LEUTL FEL

    SciTech Connect

    Huang, Z.; Fawley, W.M.

    2001-07-01

    While the long-pulse, coasting beam model is often used in analysis and simulation of self-amplified spontaneous emission (SASE) free-electron lasers (FELs), many current SASE demonstration experiments employ relatively short electron bunches whose pulse length is on the order of the radiation slippage length. In particular, the low-energy undulator test line (LEUTL) FEL at the Advanced Photon Source has recently lased and nominally saturated in both visible and near-ultraviolet wavelength regions with a sub-ps pulse length that is somewhat shorter than the total slippage length in the 22-m undulator system. In this paper we explore several characteristics of the short pulse regime for SASE FELs with the multidimensional, time-dependent simulation code GINGER, concentrating on making a direct comparison with the experimental results from LEUTL. Items of interest include the radiation gain length, pulse energy, saturation position, and spectral bandwidth. We address the importance of short-pulse effects when scaling the LEUTL results to proposed x-ray FELs and also briefly discuss the possible importance of coherent spontaneous emission at startup.

  5. Output characteristics of SASE-driven short-wavelength FELs

    NASA Astrophysics Data System (ADS)

    Fawley, William M.

    1997-05-01

    This paper investigates various properties of the 'microspikes' associated with self-amplified spontaneous emission (SASE) in a short wavelength free-electron laser (FEL). Using results from the 2-D numerical simulation code GINGER, we confirm theoretical predictions such as the convective group velocity in the exponential gain regime. In the saturated gain regime beyond the initial saturation, we find that the average radiation power continues to grow with an approximately linearly dependence upon undulator length. Moreover, the spectrum significantly broadens and shifts in wavelength to the redward direction, with P(omega) approaching a constant, asymptotic value. This is in marked contrast to the exponential gain regime where the spectrum steadily narrows, P(omega) grows, and the central wavelength remains constant with z. Via use of a spectrogram diagnostic S(omega, t), it appears that the radiation pattern in the saturated gain regime is composed of an ensemble of distinct 'sinews' whose widths (Delta) (lambda) remain approximately constant but whose central wavelengths can 'chirp' by varying a small extent with t.

  6. The surface modification of tooth dentine with a Free Electron Laser (FEL)

    NASA Astrophysics Data System (ADS)

    Ogino, Seiji; Awazu, Kunio

    1998-09-01

    Free Electron Laser (FEL) with the wide wavelength tunability has been developed and used for various applications. The FEL gives high efficiency for the photo-induced ablation when the laser is tuned to an absorption maximum of the target. The FEL was tuned to 9.4 μm, which is an absorption maximum of phosphoric acid ion, a known major component of dentine. The FEL pulse length was several ps. The average output power was varied from 5 to 20 mW by filters. The change of irradiated dentine surface was analyzed by mass spectroscopy and Energy Dispersive X-ray (EDX) spectroscopy. Positive ions which correspond to Na +, CO 3+ and many phosphoric acid ions were measured. It was found that atomic ratio of P/Ca had reduced from 0.65-0.60. The atomic ratio of P/Ca, however had not changed with irradiation by Er:YAG laser (2.9 μm), or CO 2 laser (10.6 μm). These results indicate the selective ablation of phosphoric acid ion by the 9.4 mm FEL irradiation.

  7. Polarization control in X-ray FELs by reverse undulator tapering

    NASA Astrophysics Data System (ADS)

    Schneidmiller, E. A.; Yurkov, M. V.

    2015-05-01

    Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. The proposed method is rather universal, i.e. it can be used at SASE FELs and seeded (self-seeded) FELs, with any wavelength of interest, in a wide range of electron beam parameters, and with any repetition rate.

  8. Verification of the Solar Dynamics Observatory High Gain Antenna Pointing Algorithm Using Flight Data

    NASA Technical Reports Server (NTRS)

    Bourkland, Kristin L.; Liu, Kuo-Chia

    2011-01-01

    The Solar Dynamics Observatory (SDO), launched in 2010, is a NASA-designed spacecraft built to study the Sun. SDO has tight pointing requirements and instruments that are sensitive to spacecraft jitter. Two High Gain Antennas (HGAs) are used to continuously send science data to a dedicated ground station. Preflight analysis showed that jitter resulting from motion of the HGAs was a cause for concern. Three jitter mitigation techniques were developed and implemented to overcome effects of jitter from different sources. These mitigation techniques include: the random step delay, stagger stepping, and the No Step Request (NSR). During the commissioning phase of the mission, a jitter test was performed onboard the spacecraft, in which various sources of jitter were examined to determine their level of effect on the instruments. During the HGA portion of the test, the jitter amplitudes from the single step of a gimbal were examined, as well as the amplitudes due to the execution of various gimbal rates. The jitter levels were compared with the gimbal jitter allocations for each instrument. The decision was made to consider implementing two of the jitter mitigating techniques on board the spacecraft: stagger stepping and the NSR. Flight data with and without jitter mitigation enabled was examined, and it is shown in this paper that HGA tracking is not negatively impacted with the addition of the jitter mitigation techniques. Additionally, the individual gimbal steps were examined, and it was confirmed that the stagger stepping and NSRs worked as designed. An Image Quality Test was performed to determine the amount of cumulative jitter from the reaction wheels, HGAs, and instruments during various combinations of typical operations. The HGA-induced jitter on the instruments is well within the jitter requirement when the stagger step and NSR mitigation options are enabled.

  9. Longitudinal stabilisation of bunched beams in a FEL storage ring

    NASA Astrophysics Data System (ADS)

    Migliorati, M.; Palumbo, L.; Dattoli, G.; Mezi, L.; Renieri, A.; Voykov, G. K.

    1997-02-01

    Experimental observations on FEL Storage Rings (Aco, Super-Aco, VEPP3, TERAS) have shown that in a storage ring with an operating FEL there is a mutual effect between the FEL operational mode and the beam longitudinal distribution. The main effects are the birth of a macro-temporal structure of the FEL radiation and a suppression of the synchrotron sidebands, evidence of beam stabilisation against the microwave instabilities. In this paper we discuss the main features of the beam dynamics analysed with a simulation code recently developed, which includes the FEL-beam interaction. Furtherly, we propose an heuristic model which enable to describe in a simple way the overall system.

  10. Study of CSR Effects in the Jefferson Laboratory FEL Driver

    SciTech Connect

    Hall, C. C.; Biedron, S.; Burleson, Theodore A.; Milton, Stephen V.; Morin, Auralee L.; Benson, Stephen V.; Douglas, David R.; Evtushenko, Pavel E.; Hannon, Fay E.; Li, Rui; Tennant, Christopher D.; Zhang, Shukui; Carlsten, Bruce E.; Lewellen, John W.

    2013-08-01

    In a recent experiment conducted on the Jefferson Laboratory IR FEL driver the effects of Coherent Synchrotron Radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR chicane. This experiment also provides a valuable opportunity to benchmark existing CSR models in a system that may not be fully represented by a 1-D CSR model. Here we present results from this experiment and compare to initial simulations of CSR in the magnetic compression chicane of the machine. Finally, we touch upon the possibility for CSR induced microbunching gain in the magnetic compression chicane, and show that parameters in the machine are such that it should be thoroughly damped.

  11. Liver Fatty Acid Binding Protein Gene-ablation Exacerbates Weight Gain in High-Fat Fed Female Mice

    PubMed Central

    McIntosh, Avery L.; Atshaves, Barbara P.; Landrock, Danilo; Landrock, Kerstin K.; Martin, Gregory G.; Storey, Stephen M.; Kier, Ann B.; Schroeder, Friedhelm

    2013-01-01

    Loss of liver fatty acid binding protein (L-FABP) decreases long chain fatty acid uptake and oxidation in primary hepatocytes and in vivo. On this basis, L-FABP gene ablation would potentiate high-fat diet-induced weight gain and weight gain/energy intake. While this was indeed the case when L-FABP null (−/−) mice on the C57BL/6NCr background were pair-fed high fat diet, whether this would also be observed under high-fat diet fed ad libitum was not known. Therefore, this possibility was examined in female L-FABP (−/−) mice on the same background. L-FABP (−/−) mice consumed equal amounts of defined high-fat or isocaloric control diets fed ad libitum. However, on the ad libitum fed high-fat diet the L-FABP (−/−) mice exhibited: 1) Decreased hepatic long chain fatty acid (LCFA) β-oxidation as indicated by lower serum β–hydroxybutyrate level; 2) Decreased hepatic protein levels of key enzymes mitochondrial (rate limiting carnitine palmitoyl acyltransferase A1, CPT1A; HMG-CoA synthase) and peroxisomal (acyl CoA oxidase 1, ACOX1) LCFA β-oxidation; 3) Increased fat tissue mass (FTM) and FTM/energy intake to the greatest extent; and 4) Exacerbated body weight gain, weight gain/energy intake, liver weight, and liver weight/body weight to the greatest extent. Taken together, these findings showed that L-FABP gene-ablation exacerbated diet-induced weight gain and fat tissue mass gain in mice fed high-fat diet ad libitum—consistent with the known biochemistry and cell biology of L-FABP. PMID:23539345

  12. High energy gain in three-dimensional simulations of light sail acceleration

    SciTech Connect

    Sgattoni, A.; Sinigardi, S.; Macchi, A.

    2014-08-25

    The dynamics of radiation pressure acceleration in the relativistic light sail regime are analysed by means of large scale, three-dimensional (3D) particle-in-cell simulations. Differently to other mechanisms, the 3D dynamics leads to faster and higher energy gain than in 1D or 2D geometry. This effect is caused by the local decrease of the target density due to transverse expansion leading to a “lighter sail.” However, the rarefaction of the target leads to an earlier transition to transparency limiting the energy gain. A transverse instability leads to a structured and inhomogeneous ion distribution.

  13. FELS FOUNDATION PROJECT FOR DEVELOPING YOUTH POTENTIAL.

    ERIC Educational Resources Information Center

    BAIR, ROBERT A.; AND OTHERS

    THE OPERATION OF THE FELS FOUNDATION PROJECT FOR DEVELOPING YOUTH POTENTIAL IN HANFORD, CALIFORNIA, IS DESCRIBED. OF GENERAL CONCERN WAS THE PREPARATION OF CULTURALLY DEPRIVED CHILDREN FOR SCHOOL EXPERIENCES AND FOR FUTURE EMPLOYMENT. A MAJOR GOAL WAS TO IMPROVE THE SELF-IMAGE OF THE CHILDREN AND TO ASSIST THE PARENTS AND CHILDREN IN PROVIDING…

  14. FEL-based transient grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Bencivenga, F.; Cucini, R.; Capotondi, F.; Battistoni, A.; Mincigrucci, R.; Giangrisostomi, E.; Gessini, A.; Manfredda, M.; Nikolov, I. P.; Pedersoli, E.; Principi, E.; Svetina, C.; Parisse, P.; Casolari, F.; Danailov, M. B.; Kiskinova, M.; Masciovecchio, C.

    2015-05-01

    In this manuscript we report on a compact experimental set-up ("mini-TIMER") conceived for transient grating (TG) experiments based on free electron laser (FEL) radiation. This set-up has been tested at the seeded FEL facility FERMI (Elettra, Trieste, Italy) and allowed us to observe the first FEL-stimulated TG signal. This experimental result is of the greatest relevance in the context of developing coherent non-linear optical methods into the extreme ultraviolet (EUV) and soft X-ray (SXR) range. Such a challenging task will be addressed in the next future at FERMI by using the present set-up and the forthcoming EIS-TIMER beamline, which is being installed at FERMI and will start the commissioning phase in the second semester 2015. The possibility to use TGs generated by FEL radiation at sub-optical wavelengths would allow developing EUV/SXR four-wave-mixing (FWM) applications, so far considered only theoretically and widely believed to be potentially able to provide major breakthroughs in several fields of science.

  15. UCSB FEL user mode adaption project

    NASA Astrophysics Data System (ADS)

    Jaccarino, Vincent

    1992-04-01

    This research sponsored by the SDIO Biomedical and Materials Sciences FEL Program held the following objectives: Provide a facility in which in-house and outside user research in the materials and biological sciences can be carried out in the Far Infrared using-the unique properties of the UCSB electrostatic accelerator-driven FEL; Develop and implement new FEL concepts and FIR technology and encourage the transfer and application of this research; Train graduate students, post doctoral researchers and technical personnel in varied aspects of scientific user disciplines, FEL science and FIR technology in a cooperative, interdisciplinary environment. In summary, a free electron laser facility has been developed which is operational from 200 GHz, (6.6 cm exp -1), to 4.8 THz, (160 cm exp -1) tunable under computer control and able to deliver kilowatts of millimeter wave and far-infrared power. This facility has a well equipped user lab that has been used to perform ground breaking experiments in scientific areas as diverse as bio-physics. Nine graduate students and post doctoral researchers have been trained in the operation, use and application of these free-electron lasers.

  16. Modelling Plant and Soil Nitrogen Feedbacks Affecting Forest Carbon Gain at High CO2

    NASA Astrophysics Data System (ADS)

    McMurtrie, R. E.; Norby, R. J.; Franklin, O.; Pepper, D. A.

    2007-12-01

    Short-term, direct effects of elevated atmospheric CO2 concentrations on plant carbon gain are relatively well understood. There is considerable uncertainty, however, about longer-term effects, which are influenced by various plant and ecosystem feedbacks. A key feedback in terrestrial ecosystems occurs through changes in plant carbon (C) allocation patterns. For instance, if high CO2 were to increase C allocation to roots, then plants may experience positive feedback through improved plant nutrition. A second type of feedback, associated with decomposition of soil-organic matter, may reduce soil-nutrient availability at high CO2. This paper will consider mechanistic models of both feedbacks. Effects of high CO2 on plant C allocation will be investigated using a simple model of forest net primary production (NPP) that incorporates the primary mechanisms of plant carbon and nitrogen (N) balance. The model called MATE (Model Any Terrestrial Ecosystem) includes an equation for annual C balance that depends on light- saturated photosynthetic rate and therefore on [CO2], and an equation for N balance incorporating an expression for N uptake as a function of root mass. The C-N model is applied to a Free Air CO2 Exchange (FACE) experiment at Oak Ridge National Laboratory (ORNL) in Tennessee, USA, where closed-canopy, monoculture stands of the deciduous hardwood sweetgum ( Liquidambar styraciflua) have been growing at [CO2] of 375 and 550 ppm for ten years. Features of this experiment are that the annual NPP response to elevated CO2 has averaged approximately 25% over seven years, but that annual fine-root production has almost doubled on average, with especially large increases in later years of the experiment (Norby et al. 2006). The model provides a simple graphical approach for analysing effects of elevated CO2 and N supply on leaf/root/wood C allocation and productivity. It simulates increases in NPP and fine-root production at the ORNL FACE site that are consistent

  17. The Linguistic Gains and Acculturation of American High School Students on Exchange Programs in Germany

    ERIC Educational Resources Information Center

    Lovitt, Ashli

    2013-01-01

    There has been a sharp rise in study abroad participation over the last few decades (Institute for International Education, 2011), which can largely be explained by the rise of short-term study abroad programs. While there is much to be gained from participation in such programs, mid-length and year programs may offer the greatest benefits for…

  18. High-temporal contrast using low-gain optical parametric amplification

    SciTech Connect

    Shah, Rahul C; Johnson, Randall P; Shimada, Tsutomu; Flippo, Kirk A; Fernandez, Juan C; Hegelich, Bjorn M

    2008-01-01

    We demonstrate the use of low-gain optical parametric amplification (OPA) as a means of improving temporal contrast to a detection-limited level 10{sup -10}. 250 {mu}J, 500 fs pulses of 1053 nm are frequency doubled and subsequently restored to the original wavelength by OPA with >10% efficiency.

  19. Quasi-real-time photon pulse duration measurement by analysis of FEL radiation spectra.

    PubMed

    Engel, Robin; Düsterer, Stefan; Brenner, Günter; Teubner, Ulrich

    2016-01-01

    For photon diagnostics at free-electron lasers (FELs), the determination of the photon pulse duration is an important challenge and a complex task. This is especially true for SASE FELs with strongly fluctuating pulse parameters. However, most techniques require an extensive experimental setup, data acquisition and evaluation time, limiting the usability in all-day operation. In contrast, the presented work uses an existing approach based on the analysis of statistical properties of measured SASE FEL spectra and implements it as a software tool, integrated in FLASH's data acquisition system. This allows the calculation of the average pulse durations from a set of measured spectral distributions with only seconds of delay, whenever high-resolution spectra are recorded. PMID:26698053

  20. Quasi-real-time photon pulse duration measurement by analysis of FEL radiation spectra

    PubMed Central

    Engel, Robin; Düsterer, Stefan; Brenner, Günter; Teubner, Ulrich

    2016-01-01

    For photon diagnostics at free-electron lasers (FELs), the determination of the photon pulse duration is an important challenge and a complex task. This is especially true for SASE FELs with strongly fluctuating pulse parameters. However, most techniques require an extensive experimental setup, data acquisition and evaluation time, limiting the usability in all-day operation. In contrast, the presented work uses an existing approach based on the analysis of statistical properties of measured SASE FEL spectra and implements it as a software tool, integrated in FLASH’s data acquisition system. This allows the calculation of the average pulse durations from a set of measured spectral distributions with only seconds of delay, whenever high-resolution spectra are recorded. PMID:26698053

  1. IR-FEL-induced green fluorescence protein (GFP) gene transfer into plant cell

    NASA Astrophysics Data System (ADS)

    Awazu, Kunio; Kinpara, Takeshi; Tamiya, Eiichi

    2002-05-01

    A Free Electron Laser (FEL) holds potential for various biotechnological applications due to its characteristics such as flexible wavelength tunability, short pulse and high peak power. We could successfully introduce the Green Fluorescent Protein (GFP) gene into tobacco BY2 cells by IR-FEL laser irradiation. The irradiated area of the solution containing BY2 cells and plasmid was about 0.1 mm 2. FEL irradiation at a wavelength of 5.75 and 6.1 μm, targeting absorption by the ester bond of the lipid and the amide I bond of the protein, respectively, was shown to cause the introduction of the fluorescent dye into the cell. On the other hand, transient expression of the GFP fluorescence was only observed after irradiation at 5.75 μm. The maximum transfer efficiency was about 0.5%.

  2. The research facilities of the Duke FEL Laboratory - uniqueness and challenges

    SciTech Connect

    Madey, J.M.J.; Barnett, G.; Burnham, B.

    1995-12-31

    FEL light sources offer unique promise as broadly tuneable, high brightness sources of radiation throughout the electromagnetic spectrum. But the effective utilization of these new light sources also raises a series of unprecedented issues and challenges arising, in general, from the limited number of beamlines which can be supported by a single source. The cost effective utilization of this technology therefore requires emphasis on (1) the realization of one or more truly unique research capabilities, (2) the optimization of access to the research beamlines which are available, and (3) the management and support services required by users to maximize their productivity. The experience we have acquired in the development and operation of the facilities of the Duke FEL Lab provide a point of reference which may prove useful to other research-oriented FEL facilities.

  3. FEL potential of eRHIC

    SciTech Connect

    Litvinenko, V.N.; Ben-Zvi, I.; Hao, Y.; Kao, C-C.; Kayran, D.; Murphy, J.B.; Ptitsyn, V.; Trbojevic, D.; Tsoupas, N.

    2010-08-23

    Brookhaven National Laboratory plans to build a 5-to-30 GeV energy-recovery linac (ERL) for its future electron-ion collider, eRHIC. In past few months, the Laboratory turned its attention to the potential of this unique machine for free electron lasers (FELS), which we initially assessed earlier. In this paper, we present our current vision of a possible FEL farm, and of narrow-band FEL-oscillators driven by this accelerator. eRHIC, the proposed electron-ion collider at BNL, takes advantage of the existing Relativistic Heavy Ion Collider (RHIC) complex. Plans call for adding a six-pass super-conducting (SRF) ERL to this complex to collide polarized- and unpolarized- electron beams with heavy ions (with energies up to 130 GeV per nucleon) and with polarized protons (with energies up to 325 GeV). RHIC, with a circumference of 3.834 km, has three-fold symmetry and six straight sections each {approx} 250 m long. Two of these straight sections will accommodate 703-MHz SRF linacs. The maximum energy of the electron beam in eRHIC will be reached in stages, from 5 GeV to 30 GeV, by increasing the lengths of its SRF linacs. We plan to install at the start the six-pass magnetic system with small gap magnets. The structure of the eRHIC's electron beam will be identical with that of its hadron beam, viz., 166 bunches will be filled, reserving about a one-microsecond gap for the abort kicker. With modest modifications, we can assure that eRHIC's ERL will become an excellent driver for continuous wave (CW) FELs (see Fig.1). The eRHIC's beam structure will support the operation of several such FELs in parasitic mode.

  4. High Average Power Operation of a Scraper-Outcoupled Free-Electron Laser

    SciTech Connect

    Michelle D. Shinn; Chris Behre; Stephen Vincent Benson; Michael Bevins; Don Bullard; James Coleman; L. Dillon-Townes; Tom Elliott; Joe Gubeli; David Hardy; Kevin Jordan; Ronald Lassiter; George Neil; Shukui Zhang

    2004-08-01

    We describe the design, construction, and operation of a high average power free-electron laser using scraper outcoupling. Using the FEL in this all-reflective configuration, we achieved approximately 2 kW of stable output at 10 um. Measurements of gain, loss, and output mode will be compared with our models.

  5. Research on synchronization of 15 parallel high gain photoconductive semiconductor switches triggered by high power pulse laser diodes

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Xia, Liansheng; Chen, Yi; Liu, Yi; Yang, Chao; Ye, Mao; Deng, Jianjun

    2015-01-01

    The synchronization of 15 parallel high gain gallium arsenide photoconductive semiconductor switches (GaAs PCSS) has been researched aiming to get higher output voltage. Each PCSS is triggered independently by a high power pulse laser diode. The pulse width, energy, peak power, and central wavelength of the laser pulse are approximately 18 ns, 360 μJ, 20 kW, and 905 nm, respectively. In the stacked Blumlein transmission lines structure, the synchronous conduction of 15 parallel GaAs PCSSs has been achieved by offering optimized bias voltage and laser parameters. The method of synchronization calculation is given, and the synchronization of the 15 parallel GaAs PCSSs is measured as 775 ps. Furthermore, influences of the bias voltage, laser parameters on the synchronization are analyzed. In the output terminal, superimposed by the output voltages of 15 Blumlein transmission lines, the total output voltage reaches up to 328 kV, which is the highest output voltage of GaAs PCSSs that has been reported so far.

  6. Pulse Length Control in an X-Ray FEL by Using Wakefields

    SciTech Connect

    Reiche, S.; Pellegrini, Claudio; Emma, P.; /UCLA /SLAC

    2008-03-18

    For the users of the high-brightness radiation sources of free-electron lasers it is desirable to reduce the FEL pulse length to 10 fs and below for time-resolved pump and probe experiments. Although it can be achieved by conventional compression methods for the electron beam or the chirped FEL pulse, the technical realization is demanding. In this presentation we study the impact of longitudinal wakefields in the undulator and how their properties can be used to reduced the amplifying part of the bunch to the desired length. Methods of actively controlling the wakefields are presented.

  7. Optimization and Modeling of the Accelerator for the FERMI @ Elettra FEL

    SciTech Connect

    Di Mitri, S.; Cornacchia, M.; Craievich, P.; Emma, P.; Huang, Z.; Wu, J.; Wang, D.; Zholents, A.; /LBL, Berkeley

    2005-09-30

    Design studies are in progress to use the existing FERMI{at}Elettra linear accelerator for a seeded harmonic cascade free-electron laser (FEL) facility [1]. This accelerator will be upgraded to 1.2 GeV and equipped with a low-emittance RF photocathode gun, laser heater, two bunch compressors, and a beam delivery system. We present an optimization study of all the components downstream of the gun, aimed at achieving the high peak current, low energy spread and low emittance electron beam necessary for the FEL. Various operational scenarios are discussed. Results of accelerator simulations including effects of space charge, coherent synchrotron radiation and wakefields are reported.

  8. Verification of the Solar Dynamics Observatory High Gain Antenna Pointing Algorithm Using Flight Data

    NASA Technical Reports Server (NTRS)

    Bourkland, Kristin L.; Liu, Kuo-Chia

    2011-01-01

    The Solar Dynamics Observatory (SDO) is a NASA spacecraft designed to study the Sun. It was launched on February 11, 2010 into a geosynchronous orbit, and uses a suite of attitude sensors and actuators to finely point the spacecraft at the Sun. SDO has three science instruments: the Atmospheric Imaging Assembly (AIA), the Helioseismic and Magnetic Imager (HMI), and the Extreme Ultraviolet Variability Experiment (EVE). SDO uses two High Gain Antennas (HGAs) to send science data to a dedicated ground station in White Sands, New Mexico. In order to meet the science data capture budget, the HGAs must be able to transmit data to the ground for a very large percentage of the time. Each HGA is a dual-axis antenna driven by stepper motors. Both antennas transmit data at all times, but only a single antenna is required in order to meet the transmission rate requirement. For portions of the year, one antenna or the other has an unobstructed view of the White Sands ground station. During other periods, however, the view from both antennas to the Earth is blocked for different portions of the day. During these times of blockage, the two HGAs take turns pointing to White Sands, with the other antenna pointing out to space. The HGAs handover White Sands transmission responsibilities to the unblocked antenna. There are two handover seasons per year, each lasting about 72 days, where the antennas hand off control every twelve hours. The non-tracking antenna slews back to the ground station by following a ground commanded trajectory and arrives approximately 5 minutes before the formerly tracking antenna slews away to point out into space. The SDO Attitude Control System (ACS) runs at 5 Hz, and the HGA Gimbal Control Electronics (GCE) run at 200 Hz. There are 40 opportunities for the gimbals to step each ACS cycle, with a hardware limitation of no more than one step every three GCE cycles. The ACS calculates the desired gimbal motion for tracking the ground station or for slewing

  9. Optical properties of the output of a high-gain, self-amplified free-electron laser.

    SciTech Connect

    Li, Y.; Lewellen, J.; Huang, Z.; Krinsky, S.; Accelerator Systems Division; BNL

    2004-01-01

    The temporal structure and phase evolutions of a high-gain, self-amplified free-electron laser are measured, including single-shot analysis and statistics over many shots. Excellent agreement with the theory of free-electron laser and photon statistics is found.

  10. Parametric x-ray FEL operating with external Bragg reflectors

    SciTech Connect

    Baryshevsky, V.G.; Batrakov, K.G.; Dubovskaya, I.Ya.

    1995-12-31

    In the crystal X-ray FELs using channeling and parametric quasi-Cherenkov mechanisms of spontaneous radiation were considered as versions of FEL allowing, in principle, to obtain coherent X-ray source. In this case a crystal is both radiator and resonator for X-rays emitted by a particle beam passing through crystal. However, it is well-known that a beam current density required for lasing is extremely high in X-ray spectral range for any radiation mechanisms and it is very important to find a way to lower its magnitude. The application of three-dimensional distributed feedback formed by dynamical diffraction of emitted photons permitted to reduce starting beam current density 10{sup 2}-10{sup 4} times up to 10{sup 9}. One of ways to lower the starting current is the formation of multi-wave distributed feedback the another one is the application of external reflectors. The thing is that lasing regime was shown to be produced at frequencies in the vicinity of degeneration point for roots of dispersion equation describing radiation modes excited in an active medium (crystal plus particle beam). Unfortunately, in case of parametric quasi-Cherenkov FEL this region coincides with the region of strong self-absorption of radiation inside a crystal. That fact, obviously, increases the starting beam current. In this report we have shown that the application of external Bragg reflectors gives the possibility to lower radiation self-absorption inside a crystal by modifying radiation modes excited in the active medium under consideration. The corresponding dispersion equation and the expression for excited modes are derived. The generation equation determining starting conditions for lasing is obtained. Using these expressions we have shown that the application of external Bragg reflectors permits to reduce starting beam current density more than 10 times.

  11. High-power gain-switched Tm(3+)-doped fiber laser.

    PubMed

    Tang, Yulong; Xu, Lin; Yang, Yi; Xu, Jianqiu

    2010-10-25

    Gain-switched by a 1.914-µm Tm:YLF crystal laser, a two-stage Tm(3+) fiber laser has been achieved 100-W level ~2-µm pulsed laser output with a slope efficiency of ~52%. With the 6-m length of Tm fiber, the laser wavelength was centered at 2020 nm with a bandwidth of ~25 nm. Based on an acousto-optic switch, the pulse repetition rate can be modulated from 500 Hz to 50 kHz, and the laser pulse width can be tuned between 75 ns and ~1 µs. The maximum pulse energy was over 10 mJ, and the maximum pulse peak power was 138 kW. By using the fiber-coiling-induced mode-filtering effect, laser beam quality of M2 = 1.01 was obtained. Further scaling the pulse energy and average power from such kind of gain-switched fiber lasers was also discussed. PMID:21164635

  12. A High Gain and Broadband C-Band Aperture-Coupled Patch Antenna

    NASA Astrophysics Data System (ADS)

    Liu, Chunheng; Lu, Yueguang; Du, Chunlei; Luo, Xiangang

    2007-12-01

    A aperture-coupled patch antenna is designed with parasitic elements connecting to the rectangle ring on the bottom of antenna substrate through metal vias, which lead the current induced by patch radiator to the top surface of antenna substrate. Therefore, the effective radiation is enhanced and higher gain is achieved. The bandwidth is broadened simultaneously due to the structure of aperture-coupled patch antenna with parasitic elements. Compared to the conventional aperture-coupled patch antenna, the antenna gain increases averagely 2 dB due to the novel structure. Compared to patch antenna of electromagnetic band-gap, the dimensions of novel patch antenna greatly decreases, which can be used as element in the array antenna. Two kinds manufactured antenna are both measured in an anechoic chamber. The good agreements between numerical simulation and experimental prototype have been obtained.

  13. High-gain wavelength-selective amplification and cavity ring down spectroscopy in a fluoride glass erbium-doped microsphere.

    PubMed

    Rasoloniaina, A; Trebaol, S; Huet, V; Le Cren, E; Nunzi Conti, G; Serier-Brault, H; Mortier, M; Dumeige, Y; Féron, P

    2012-11-15

    We experimentally demonstrate a compact optical amplifier consisting of a rare-earth-doped whispering-gallery-mode microsphere coupled via a tapered fiber. A gain up to 20 dB is reported in an erbium-doped fluoride glass microsphere 135 μm in diameter. Below the amplification regime, the optical gain is used to compensate for unavoidable losses due to surface contamination or scattering. Quality factor as high as 2×10(9) has been measured by analyzing the transient response of the microsphere excited by a dynamically shifted frequency input signal. PMID:23164896

  14. High Risk of Obesity and Weight Gain for HIV-Infected Uninsured Minorities

    PubMed Central

    Taylor, Barbara S.; Liang, Yuanyuan; Garduño, L. Sergio; Walter, Elizabeth A.; Gerardi, Margit; Anstead, Gregory M.; Bullock, Delia; Turner, Barbara J.

    2014-01-01

    Background Obesity and HIV disproportionately affect minorities and have significant health risks, but few studies have examined disparities in weight change in HIV-seropositive (HIV+) cohorts. Objective To determine racial and health insurance disparities in significant weight gain in a predominately Hispanic HIV+ cohort. Methods Our observational cohort study of 1,214 non-underweight HIV+ adults from 2007-2010 had significant weight gain (≥3% annual BMI increase) as primary outcome. The secondary outcome was continuous BMI over time. A four-level race-ethnicity/insurance predictor reflected the interaction between race-ethnicity and insurance: insured white (non-Hispanic), uninsured white, insured minority (Hispanic or black), or uninsured minority. Logistic and mixed effects models adjusted for: baseline BMI; age; gender; household income; HIV transmission category; antiretroviral therapy type; CD4+ count; plasma HIV-1 RNA; observation months; and visit frequency. Results The cohort was 63% Hispanic and 14% black; 13.3% were insured white, 10.0% uninsured white, 40.9% insured minority, and 35.7% uninsured minority. At baseline, 37.5% were overweight, 22.1% obese. Median observation was 3.25 years. 24.0% had significant weight gain, which was more likely for uninsured minority patients than insured whites (adjusted odds ratio=2.85 , 95%CI: 1.66, 4.90). The rate of BMI increase in mixed effects models was greatest for uninsured minorities. Of 455 overweight at baseline, 29% were projected to become obese in 4 years. Conclusions and Relevance In this majority Hispanic HIV+ cohort, 60% were overweight or obese at baseline, and uninsured minority patients gained weight more rapidly. These data should prompt greater attention by HIV providers to prevention of obesity. PMID:24121754

  15. High Gain, Fast Scan, Broad Spectrum, Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM

    SciTech Connect

    David OHara; Dr. Eric Lochmer

    2003-09-12

    Parallax Research, Inc. proposes to produce a new type of x-ray spectrometer for use with Scanning Electron Microscopy (SEM) that would have the energy resolution of WDS and the ease of use of EDS with sufficient gain for lower energies that it can be used at low beam currents as is EDS. Parallax proposes to do this by development of new multiple reflection x-ray collimation optics, new diffractor technology, new detector technology and new scan algorithms.

  16. Novel Design of a High-gain and Wideband Fabry-Pérot Cavity Antenna Using a Tapered AMC Substrate

    NASA Astrophysics Data System (ADS)

    Yeo, Junho; Kim, Dongho

    2009-03-01

    A high-gain and wideband electromagnetic bandgap (EBG) resonator antenna with a tapered artificial magnetic conductor (AMC) ground plane is presented. The proposed EBG resonator antenna is comprised of a frequency selective surface (FSS) superstrate with a strip dipole array and an AMC ground plane with tapered rectangular patches. The realized gain and the bandwidth of the antenna can be improved simultaneously by using the tapered AMC where the phase difference of the reflected waves from the patches with different length is within 180° and the destructive interference among them can be considerably reduced. The maximum gain is increased about 2˜3 dB and the bandwidth is improved about 2.5 times compared to when the uniform AMC is used.

  17. Wideband and flat-gain amplifier based on high concentration erbium-doped fibres in parallel double-pass configuration

    SciTech Connect

    Hamida, B A; Cheng, X S; Harun, S W; Naji, A W; Arof, H; Al-Khateeb, W; Khan, S; Ahmad, H

    2012-03-31

    A wideband and flat gain erbium-doped fibre amplifier (EDFA) is demonstrated using a hybrid gain medium of a zirconiabased erbium-doped fibre (Zr-EDF) and a high concentration erbium-doped fibre (EDF). The amplifier has two stages comprising a 2-m-long ZEDF and 9-m-long EDF optimised for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fibre Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achieved with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.

  18. Ultra-long and high-stability random laser based on EDF gain-media and Rayleigh scattering distributed mirror

    NASA Astrophysics Data System (ADS)

    Aporta, I.; Quintela, M. A.; Rodríguez-Cobo, L.; López-Higuera, J. M.

    2015-09-01

    An ultra-long, low-threshold and high-stability Random distributed feedback fiber laser (RDF-FL) based on Erbium-doped fiber (EDF) to provide the gain medium, and single mode fiber (SMF) as a distributed mirror in combination with fiber-brag grating (FBG) to form the cavity is proposed in this paper. Typical random laser radiation for a SMF length of 50 km with a low-threshold of 10 dBm and high-stability (~0.1 dB) is achieved, thanks to the design of the cavity and the high-gain from the pumped erbium-doped fiber. Besides, 200 km quasi-losses random laser due to the distributed mirror and the FBG reflector is demonstrated.

  19. Numerical study of X-ray FELS including quantum fluctuation

    NASA Astrophysics Data System (ADS)

    Reiche, S.; Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

    1997-06-01

    One of the fundamental limitations towards achieving very short wavelength in a self amplified spontaneous emission free electron laser (SASE FEL) is connected with the energy diffusion in the electron beam due to quantum fluctuations of undulator radiation. Parameters of the LCLS and TESLA X-ray FEL projects are very close to this limit and there exists necessity in upgrading FEL simulation codes for optimization of SASE FEL for operation at a shortest possible wavelength. In this report we describe a one-dimensional FEL simulation code taking into account the effects of incoherent undulator radiation. Using similarity techniques we have calculated universal functions describing degradation of the FEL process due to quantum fluctuations of undulator radiation.

  20. Duke storage rink UV/VUV FEL: Status and prospects

    SciTech Connect

    Litvinenko, V.N.; Burnham, B.; Madey, J.M.J.

    1995-12-31

    The 1 GeV Duke storage ring was successfully commissioned with parameters exceeding initial specification. The OK-4 FEL has arrived at the Duke FEL laboratory from the Novosibirsk Institute of Nuclear Physics. The OK-4 installation and commissioning is in progress. In this paper we describe the up-to-date status of the Duke storage ring and the OK-4 FEL. The projected performance of the OK-4 UV/VUV FEL is presented based on the electron beam parameters achieved. Initial plans to operate the OK-4 UV/VUV FEL at the Duke 1 GeV storage ring are outlined. Future plans and prospects of both the OK-4 FEL and the Duke storage ring are discussed.