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Sample records for kstar 5ghz lhcd

  1. Progress of the 2012 KSTAR experimental campaign

    NASA Astrophysics Data System (ADS)

    Oh, Yeong-Kook; Kim, W. C.; Lee, S. G.; Kim, J. Y.; Yang, H. L.; Park, K. R.; Chu, Y.; Park, M. K.; Bae, Y. S.; H; K; Kim; Kwak, J. G.; Park, H.; Choe, W. H.; Chung, K. S.; Na, Y. S.; Hwang, Y. S.; in, S. Y.; Walker, M.; Mueller, D.; Park, J.; Ahn, J. W.; Sabbagh, S. A.; Zoletnik, S.

    2012-10-01

    KSTAR device has been operated with a mission to explore the advanced physics and technologies at high performance steady-state plasma that are essential for ITER and fusion reactor development. The 2012 KSTAR campaign is conducted with experimental goals to extend H-mode over 10 sec at the plasma current in the level of 0.6 ˜ 1 MA by adopting the real-time shaping control, to investigate physics issues including L- to H-mode transition and ELM mitigation, and to support various experiments proposed by domestic and international collaborators. The available heating power in 2012 is about 5.5 MW in total including 3.5 MW NBI, 1 MW ICRF, 1 MW ECH/CD, and 0.3 MW LHCD. The upgraded diagnostic systems are Thomson scattering system, BES, two ECEI, VUV spectrometer, imaging bolometer, and FIR interferometer. In this presentation, the progress of the KSTAR experiments will be described including the hardware upgrade and physics research results.

  2. Recent experimental results of KSTAR RF heating and current drive

    SciTech Connect

    Wang, S. J. Kim, J.; Jeong, J. H.; Kim, H. J.; Joung, M.; Bae, Y. S.; Kwak, J. G.

    2015-12-10

    The overview of KSTAR activities on ICRH, LHCD and ECH/CD including the last experimental results and future plan aiming for long-pulse high-beta plasma will be presented. Recently we achieved reasonable coupling of ICRF power to H-mode plasma through several efforts to increase system reliability. Power balance will be discussed on this experiment. LHCD is still struggling in the low power regime. Review of antenna spectrum for the higher coupling in H-mode plasma will be tried. ECH/CD provides 41 sec, 0.8 MW of heating power to support high-performance long-pulse discharge. Also, 170 GHz ECH system is integrated with the Plasma Control System (PCS) for the feedback controlling of NTM. Status and plan of ECH/CD will be discussed. Finally, helicon current drive is being prepared for the next stage of KSTAR operation. The hardware preparation and the calculation results of helicon current drive in KSTAR plasma will be discussed.

  3. Recent experimental results of KSTAR RF heating and current drive

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Kim, J.; Jeong, J. H.; Kim, H. J.; Joung, M.; Bae, Y. S.; Kwak, J. G.

    2015-12-01

    The overview of KSTAR activities on ICRH, LHCD and ECH/CD including the last experimental results and future plan aiming for long-pulse high-beta plasma will be presented. Recently we achieved reasonable coupling of ICRF power to H-mode plasma through several efforts to increase system reliability. Power balance will be discussed on this experiment. LHCD is still struggling in the low power regime. Review of antenna spectrum for the higher coupling in H-mode plasma will be tried. ECH/CD provides 41 sec, 0.8 MW of heating power to support high-performance long-pulse discharge. Also, 170 GHz ECH system is integrated with the Plasma Control System (PCS) for the feedback controlling of NTM. Status and plan of ECH/CD will be discussed. Finally, helicon current drive is being prepared for the next stage of KSTAR operation. The hardware preparation and the calculation results of helicon current drive in KSTAR plasma will be discussed.

  4. Toroidal rotation studies in KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, S. G.; Lee, H. H.; Yoo, J. W.; Kim, Y. S.; Ko, W. H.; Terzolo, L.; Bitter, M.; Hill, K.; KSTAR Team

    2014-10-01

    Investigation of the toroidal rotation is one of the most important topics for the magnetically confined fusion plasma researches since it is essential for the stabilization of resistive wall modes and its shear plays an important role to improve plasma confinement by suppressing turbulent transport. The most advantage of KSTAR tokamak for toroidal rotation studies is that it equips two main diagnostics including the high-resolution X-ray imaging crystal spectrometer (XICS) and charge exchange spectroscopy (CES). Simultaneous core toroidal rotation and ion temperature measurements of different impurity species from the XICS and CES have shown in reasonable agreement with various plasma discharges in KSTAR. It has been observed that the toroidal rotation in KSTAR is faster than that of other tokamak devices with similar machine size and momentum input. This may due to an intrinsically low toroidal field ripple and error field of the KSTAR device. A strong braking of the toroidal rotation by the n = 1 non-resonant magnetic perturbations (NRMPs) also indicates these low toroidal field ripple and error field. Recently, it has been found that n = 2 NRMPs can also damp the toroidal rotation in KSTAR. The detail toroidal rotation studies will be presented. Work supported by the Korea Ministry of Science, ICT and Future Planning under the KSTAR project.

  5. A 0.5-GHz CMOS digital RF memory chip

    NASA Astrophysics Data System (ADS)

    Schnaitter, W. M.; Lewis, E. T.; Gordon, B. E.

    1986-10-01

    Digital RF memories (DRFM's) are key elements for modern radar jamming. An RF signal is sampled, stored in random access memory (RAM), and later recreated from the stored data. Here the first CMOS DRFM chip, integrating static RAM, control circuitry, and two channels of shift registers, on a single chip is described. The sample rate achieved was 0.5 GHz, VLSI density was made possible by the low-power dissipation of quiescent CMOS circuits. An 8K RAM prototype chip has been built and tested.

  6. Integrated modeling of LHCD experiment on Alcator C-Mod

    SciTech Connect

    Shiraiwa, S.; Bonoli, P.; Parker, R.; Wallace, G.

    2014-02-12

    Recent progress in integrating the latest LHCD model based on ray-tracing into the Integrated Plasma Simulator (IPS) is reported. IPS, a python based framework for time dependent tokamak simulation, was expanded recently to incorporate LHCD simulation using GENRAY/CQL3D (ray-tracing/3D Fokker-Planck package). Using GENRAY/CQL3D in the IPS framework, it becomes possible to include parasitic LHCD power loss near the plasma edge, which was found to be important in experiments particularly at high density as expected on reactors. Moreover, it allows for evolving the velocity distribution function in 4 D (ν{sub ∥}, ν⊥, r/a, t) space self-consistently. In order to validate the code, IPS is applied to LHCD experiments on Alctor C-Mod. In this paper, a LHCD experiment performed at the density of n{sub e}∼0.5×10{sup 20}m{sup −3} where good LHCD efficiency and the development of internal transport barrier (ITB) was reported, is modelled in a predictive mode and the result is compared with experiment.

  7. Integrated modeling of LHCD experiment on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Shiraiwa, S.; Bonoli, P.; Parker, R.; Wallace, G.

    2014-02-01

    Recent progress in integrating the latest LHCD model based on ray-tracing into the Integrated Plasma Simulator (IPS) is reported. IPS, a python based framework for time dependent tokamak simulation, was expanded recently to incorporate LHCD simulation using GENRAY/CQL3D (ray-tracing/3D Fokker-Planck package). Using GENRAY/CQL3D in the IPS framework, it becomes possible to include parasitic LHCD power loss near the plasma edge, which was found to be important in experiments particularly at high density as expected on reactors. Moreover, it allows for evolving the velocity distribution function in 4 D (ν∥, ν⊥, r/a, t) space self-consistently. In order to validate the code, IPS is applied to LHCD experiments on Alctor C-Mod. In this paper, a LHCD experiment performed at the density of ne˜0.5×1020m-3 where good LHCD efficiency and the development of internal transport barrier (ITB) was reported, is modelled in a predictive mode and the result is compared with experiment.

  8. Overview of KSTAR initial operation

    SciTech Connect

    Kwon, M.; Oh, Y. K.; Yang, H. L.; Na, H. K.; Kim, Y. S.; Kwak, J. G.; Kim, W. C.; Kim, J. Y.; Ahn, Joonwook; Ahn, J.W.; Bae, Y. S.; Baek, S. H.; Bak, J. G.; Bang, E. N.; Chang, C. S.; Chang, D. H.; Chavdarovski, I.; Chen, Z. Y.; Cho, K. W.; Cho, M. H.; Choe, W.; Choi, J. H.; Chu, Y.; Chung, K. S.; Diamond, P. H.; Do, H. J.; Eidietis, N. W.; England, A. C.; Grisham, L.; Hahm, T. S.; Hahn, S. H.; Han, W. S.; Hatae, T.; Hillis, D. L.; Hong, J. S.; Hong, S. H.

    2011-01-01

    Since the successful first plasma generation in the middle of 2008, three experimental campaigns were successfully made for the KSTAR device, accompanied with a necessary upgrade in the power supply, heating, wall-conditioning and diagnostic systems. KSTAR was operated with the toroidal magnetic field up to 3.6 T and the circular and shaped plasmas with current up to 700 kA and pulse length of 7 s, have been achieved with limited capacity of PF magnet power supplies. The mission of the KSTAR experimental program is to achieve steady-state operations with high performance plasmas relevant to ITER and future reactors. The first phase (2008 2012) of operation of KSTAR is dedicated to the development of operational capabilities for a super-conducting device with relatively short pulse. Development of start-up scenario for a super-conducting tokamak and the understanding of magnetic field errors on start-up are one of the important issues to be resolved. Some specific operation techniques for a super-conducting device are also developed and tested. The second harmonic pre-ionization with 84 and 110 GHz gyrotrons is an example. Various parameters have been scanned to optimize the pre-ionization. Another example is the ICRF wall conditioning (ICWC), which was routinely applied during the shot to shot interval. The plasma operation window has been extended in terms of plasma beta and stability boundary. The achievement of high confinement mode was made in the last campaign with the first neutral beam injector and good wall conditioning. Plasma control has been applied in shape and position control and now a preliminary kinetic control scheme is being applied including plasma current and density. Advanced control schemes will be developed and tested in future operations including active profiles, heating and current drives and control coil-driven magnetic perturbation.

  9. Overview of KSTAR initial operation

    SciTech Connect

    Kwon, M.; Oh, Y. K.; Yang, H. L.; Na, H. K.; Kim, Y. S.; Ahn, J.W.; Hillis, D. L.

    2011-01-01

    Since the successful first plasma generation in the middle of 2008, three experimental campaigns were successfully made for the KSTAR device, accompanied with a necessary upgrade in the power supply, heating, wall-conditioning and diagnostic systems. KSTAR was operated with the toroidal magnetic field up to 3.6 T and the circular and shaped plasmas with current up to 700 kA and pulse length of 7 s, have been achieved with limited capacity of PF magnet power supplies. The mission of the KSTAR experimental program is to achieve steady-state operations with high performance plasmas relevant to ITER and future reactors. The first phase (2008-2012) of operation of KSTAR is dedicated to the development of operational capabilities for a super-conducting device with relatively short pulse. Development of start-up scenario for a super-conducting tokamak and the understanding of magnetic field errors on start-up are one of the important issues to be resolved. Some specific operation techniques for a super-conducting device are also developed and tested. The second harmonic pre-ionization with 84 and 110 GHz gyrotrons is an example. Various parameters have been scanned to optimize the pre-ionization. Another example is the ICRF wall conditioning (ICWC), which was routinely applied during the shot to shot interval. The plasma operation window has been extended in terms of plasma beta and stability boundary. The achievement of high confinement mode was made in the last campaign with the first neutral beam injector and good wall conditioning. Plasma control has been applied in shape and position control and now a preliminary kinetic control scheme is being applied including plasma current and density. Advanced control schemes will be developed and tested in future operations including active profiles, heating and current drives and control coil-driven magnetic perturbation.

  10. Overview of KSTAR ICRF Experiments in 2008

    SciTech Connect

    Kwak, Jong-Gu; Wang, S. J.; Bae, Y. D.; Kim, S. H.; Kim, S. K.

    2009-11-26

    KSTAR is a national superconducting tokamak with the aim of a high beta operation based on AT scenarios, and ICRF heating is one of the essential tools to achieve this goal. After 12 years R and D works, ICRF system including the 2 MW transmitter and antenna was installed in 2007 and it was used for KSTAR first plasma events in 2008. In this paper, the installation processes of the ICRF system with an emphasis on the quality assurance procedures of KSTAR, as well as the results from the first RF discharge experiments for a discharge cleaning and FWEH experiments are outlined and future plan is shown.

  11. Overview of KSTAR ICRF Experiments

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Kim, S. H.; Kim, S. K.; An, C. Y.; Kwak, J. G.

    2011-12-01

    At magnetic field of 2 T, 30 MHz, 500 kW of RF power was injected for the central ion and electron heating for D(H) plasmas of KSTAR tokamak. Clear evidence of plasma temperature and stored energy elevation were observed with less impurity generation compared to the previous campaign. With a RF injection period, sawtooth stabilization was observed and this effect is thought to be caused by conductivity perturbation at sawtooth inversion radius as maximum power deposition layer is located at slightly inside of sawtooth inversion layer inferred from the profile measurement of increase in electron temperature. In contrast with previous results showing increasing RF loading resistance with RF power, stable loading resistance was obtained during the whole operation. This effect and less impurity contents suggests that the stray power absorption was lowered quite a lot.

  12. Intra-shot MSE Calibration Technique For LHCD Experiments

    SciTech Connect

    Ko, Jinseok; Scott, Steve; Shiraiwa, Syun'ichi; Greenwald, Martin; Parker, Ronald; Wallace, Gregory

    2009-11-23

    The spurious drift in pitch angle of order several degrees measured by the Motional Stark Effect (MSE) diagnostic in the Alcator C-Mod tokamak1 over the course of an experimental run day has precluded direct utilization of independent absolute calibrations. Recently, the underlying cause of the drift has been identified as thermal stress-induced birefringence in a set of in-vessel lenses. The shot-to-shot drift can be avoided by using MSE to measure only the change in pitch angle between a reference phase and a phase of physical interest within a single plasma discharge. This intra-shot calibration technique has been applied to the Lower Hybrid Current Drive (LHCD) experiments and the measured current profiles qualitatively demonstrate several predictions of LHCD theory such as an inverse dependence of current drive efficiency on the parallel refractive index and the presence of off-axis current drive.

  13. Simulation study of proposed off-midplane lower hybrid current drive in KSTAR

    NASA Astrophysics Data System (ADS)

    Bae, Young-soon; Shiraiwa, S.; Bonoli, P.; Wallace, G.; Wright, J. C.; Parker, R.; Kim, J. H.; Namkung, W.; Cho, M. H.; Park, B. H.; Yoon, S. W.; Oh, Y. K.; Park, H.

    2016-07-01

    A new proposal of lower hybrid (LH) wave launching is studied for efficient current drive aiming for high performance H-mode operation in Korea Superconducting Tokamak Advanced Research (KSTAR). This new concept is the off-midplane launch which results in a rapid up-shift of the parallel component of refractive index and hence simultaneously maintains good wave accessibility and efficient single pass absorption via Landau damping. In order to locate an optimal position of the launcher in the poloidal direction, the ray-tracing and Fokker–Planck codes were used. Based on a survey of the LH wave launch parameters and operation conditions including the compatibility issues with the existing in-vessel components, the LH wave launch from the top position near the upper X-point of the plasma separatrix provides the possibility to eliminate the accessibility problem and reduce parasitic edge loss for the KSTAR high performance H-mode operation scenario using 5 GHz lower hybrid current drive.

  14. Simulation study of proposed off-midplane lower hybrid current drive in KSTAR

    NASA Astrophysics Data System (ADS)

    Bae, Young-soon; Shiraiwa, S.; Bonoli, P.; Wallace, G.; Wright, J. C.; Parker, R.; Kim, J. H.; Namkung, W.; Cho, M. H.; Park, B. H.; Yoon, S. W.; Oh, Y. K.; Park, H.

    2016-07-01

    A new proposal of lower hybrid (LH) wave launching is studied for efficient current drive aiming for high performance H-mode operation in Korea Superconducting Tokamak Advanced Research (KSTAR). This new concept is the off-midplane launch which results in a rapid up-shift of the parallel component of refractive index and hence simultaneously maintains good wave accessibility and efficient single pass absorption via Landau damping. In order to locate an optimal position of the launcher in the poloidal direction, the ray-tracing and Fokker-Planck codes were used. Based on a survey of the LH wave launch parameters and operation conditions including the compatibility issues with the existing in-vessel components, the LH wave launch from the top position near the upper X-point of the plasma separatrix provides the possibility to eliminate the accessibility problem and reduce parasitic edge loss for the KSTAR high performance H-mode operation scenario using 5 GHz lower hybrid current drive.

  15. Design of a Doppler reflectometer for KSTAR

    SciTech Connect

    Lee, K. D. Nam, Y. U.; Seo, Seong-Heon; Kim, Y. S.

    2014-11-15

    A Doppler reflectometer has been designed to measure the poloidal propagation velocity on the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. It has the operating frequency range of V-band (50-75 GHz) and the monostatic antenna configuration with extraordinary mode (X-mode). The single sideband modulation with an intermediate frequency of 50 MHz is used for the heterodyne measurement with the 200 MHz in-phase and quadrature (I/Q) phase detector. The corrugated conical horn antenna is used to approximate the Gaussian beam propagation and it is installed together with the oversized rectangular waveguides in the vacuum vessel. The first commissioning test of the Doppler reflectometer system on the KSTAR tokamak is planned in the 2014 KSTAR experimental campaign.

  16. High-power ICRF and LHCD experiments on Tore Supra

    SciTech Connect

    Saoutic, B.; Beaumont, B.; Becoulet, A.; Bizarro, J.P.; Fraboulet, D.; Garbet, X.; Goniche, M.; Guiziou, L.; Hoang, G.T.; Hutter, T.; Joffrin, E.; Kuus, H.; Litaudon, X.; Mollard, P.; Moreau, D.; Nguyen, F.; Pecquet, A.L.; Peysson, Y.; Rey, G.; van Houtte, D.; Zabiego, M. )

    1994-10-15

    For a given ICRF power, the sawtooth-free period duration increases with plama density. This trend, correlated with an increasing soft X-ray inversion radius, clearly shows a better stabilization by hot ions at higher density. A tentative explanation is given through a full modeling of the hot ion anisotropy using a Fokker Planck code coupled with a 1/2 D power balance code simulating experimental data. A linear stability analysis of the kink/tearing m=1 mode, in terms of a MHD kinetic functional, shows that the anisotropy of the distribution function may amplify the effect of the hot ion pressure gradient. A two-fold lengthening of the sawtooth-free period is obtained when applying LHCD to ICRF heated plasmas. Analysis of polarimetric data shows that, instead of the continuous decrease of the central safety factor observed when using ICRF alone, the q value freezes'' when LHCD power exceeds 3 MW. This demonstrates a current profile control effect opening the way towards steady-state stabilization. Working with both ICRH and LHCD on the same target plasma allows thorough comparisons of transport with different power deposition profiles and coupling mechanisms. The energy stored in electrons is the same although the electronic temperature gradients are quite different. Nevertheless, due to better ion heating, the energy life time (discarding hot ions contribution) is always higher with ICRH. Local transport analyses allow comparisons between both heating schemes for different confinement situations.

  17. Investigations of LHCD induced plasma rotation in Tore Supra

    NASA Astrophysics Data System (ADS)

    Chouli, B.; Fenzi, C.; Garbet, X.; Bourdelle, C.; Sarazin, Y.; Rice, J.; Aniel, T.; Artaud, J.-F.; Baiocchi, B.; Basiuk, V.; Cottier, P.; Decker, J.; Imbeaux, F.; Irishkin, M.; Mazon, D.; Schneider, M.; the Tore Supra Team

    2015-12-01

    Theoretical investigations are performed in order to explain the plasma rotation increments induced by lower hybrid current drive (LHCD) in Tore Supra and the results are compared to the experimental observations. The intrinsic toroidal rotation is governed by several mechanisms in concert. The impact of the LHCD on each involved mechanism is analyzed. The neoclassical toroidal rotation is always in the counter-current direction. The toroidal diamagnetic velocity is of the order of the experimental toroidal velocity. At high plasma current the rotation evolution in the lower hybrid (LH) phase is controlled by the neoclassical friction force due to the trapped ions in banana trajectories through the toroidal diamagnetic velocity. This force results in the counter-current increment as observed in the experimental measurement of toroidal rotation. At low plasma current the rotation is dominated by momentum turbulent transport when the LH waves are applied. The Reynolds stress grows strongly compared to the high plasma current case and acts as a co-current force through its residual stress contribution. Momentum transport simulations are also performed with CRONOS (Artaud et al 2010) in order to assess the rotation increments induced by LHCD.

  18. Electron cyclotron emission diagnostics on KSTAR tokamak.

    PubMed

    Jeong, S H; Lee, K D; Kogi, Y; Kawahata, K; Nagayama, Y; Mase, A; Kwon, M

    2010-10-01

    A new electron cyclotron emission (ECE) diagnostics system was installed for the Second Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The new ECE system consists of an ECE collecting optics system, an overmode circular corrugated waveguide system, and 48 channel heterodyne radiometer with the frequency range of 110-162 GHz. During the 2 T operation of the KSTAR tokamak, the electron temperatures as well as its radial profiles at the high field side were measured and sawtooth phenomena were also observed. We also discuss the effect of a window on in situ calibration.

  19. Electron cyclotron emission diagnostics on KSTAR tokamak

    SciTech Connect

    Jeong, S. H.; Lee, K. D.; Kwon, M.; Kogi, Y.; Kawahata, K.; Nagayama, Y.; Mase, A.

    2010-10-15

    A new electron cyclotron emission (ECE) diagnostics system was installed for the Second Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The new ECE system consists of an ECE collecting optics system, an overmode circular corrugated waveguide system, and 48 channel heterodyne radiometer with the frequency range of 110-162 GHz. During the 2 T operation of the KSTAR tokamak, the electron temperatures as well as its radial profiles at the high field side were measured and sawtooth phenomena were also observed. We also discuss the effect of a window on in situ calibration.

  20. ECEI/MIR Optical Designs for KSTAR

    NASA Astrophysics Data System (ADS)

    Shen, Z.; Liang, T.; Kong, X.; Domier, C. W.; Luhmann, N. C., Jr.; Park, H. K.

    2007-11-01

    2-D plasma imaging diagnostic system is being developed for the KSTAR tokomak to image electron temperature profiles and fluctuations via Electron Cyclotron Emission Imaging (ECEI) and electron density fluctuations via Microwave Imaging Reflectometry (MIR). Optical designs have been developed for both low field (1.5-2.0 T) and high field (3.0-3.5 T) operation scenarios. Each ECEI system consists of a pair of 24 element mixer arrays producing 768 (24x32) channel temperature fluctuation images. Each MIR system consists of a single 16 element mixer array producing 128 (16x8) channel density fluctuation images. Use of in-vessel reflective optics permits both systems to view the KSTAR plasma through a relatively small vacuum window. System details, including preliminary optical and electronics designs for low and high field configurations, will be presented.

  1. An overview of KSTAR results

    NASA Astrophysics Data System (ADS)

    Kwak, Jong-Gu; Oh, Y. K.; Yang, H. L.; Park, K. R.; Kim, Y. S.; Kim, W. C.; Kim, J. Y.; Lee, S. G.; Na, H. K.; Kwon, M.; Lee, G. S.; Ahn, H. S.; Ahn, J.-W.; Bae, Y. S.; Bak, J. G.; Bang, E. N.; Chang, C. S.; Chang, D. H.; Chen, Z. Y.; Cho, K. W.; Cho, M. H.; Choi, M.; Choe, W.; Choi, J. H.; Chu, Y.; Chung, K. S.; Diamond, P.; Delpech, L.; Do, H. J.; Eidietis, N.; England, A. C.; Ellis, R.; Evans, T.; Choe, G.; Grisham, L.; Gorelov, Y.; Hahn, H. S.; Hahn, S. H.; Han, W. S.; Hatae, T.; Hillis, D.; Hoang, T.; Hong, J. S.; Hong, S. H.; Hong, S. R.; Hosea, J.; Humphreys, D.; Hwang, Y. S.; Hyatt, A.; Ida, K.; In, Y. K.; Ide, S.; Jang, Y. B.; Jeon, Y. M.; Jeong, J. I.; Jeong, N. Y.; Jeong, S. H.; Jin, J. K.; Joung, M.; Ju, J.; Kawahata, K.; Kim, C. H.; Kim, Hee-Su; Kim, H. S.; Kim, H. J.; Kim, H. K.; Kim, H. T.; Kim, J. H.; Kim, J.; Kim, J. C.; Kim, Jong-Su; Kim, Jung-Su; Kim, J. H.; Kim, Kyung-Min; Kim, K. J.; Kim, K. P.; Kim, M. K.; Kim, S. T.; Kim, S. W.; Kim, Y. J.; Kim, Y. K.; Kim, Y. O.; Ko, J. S.; Ko, W. H.; Kogi, Y.; Kolemen, E.; Kong, J. D.; Kwak, S. W.; Kwon, J. M.; Kwon, O. J.; Lee, D. G.; Lee, D. R.; Lee, D. S.; Lee, H. J.; Lee, J.; Lee, J. H.; Lee, K. D.; Lee, K. S.; Lee, S. H.; Lee, S. I.; Lee, S. M.; Lee, T. G.; Lee, W.; Lee, W. L.; Lim, D. S.; Litaudon, X.; Lohr, J.; Mueller, D.; Moon, K. M.; Na, D. H.; Na, Y. S.; Nam, Y. U.; Namkung, W.; Narihara, K.; Oh, S. T.; Oh, D. G.; Ono, T.; Park, B. H.; Park, D. S.; Park, G. Y.; Park, H.; Park, H. T.; Park, J. K.; Park, J. S.; Park, M. K.; Park, S. H.; Park, S.; Park, Y. M.; Park, Y. S.; Parker, R.; Rhee, D. R.; Sabbagh, S. A.; Sakamoto, K.; Shiraiwa, S.; Seo, D. C.; Seo, S. H.; Seol, J. C.; Shi, Y. J.; Son, S. H.; Song, N. H.; Suzuki, T.; Terzolo, L.; Walker, M.; Wallace, G.; Watanabe, K.; Wang, S. J.; Woo, H. J.; Woo, I. S.; Yagi, M.; Yu, Y. W.; Yamada, I.; Yonekawa, Y.; Yoo, C. M.; You, K. I.; Yoo, J. W.; Yun, G. S.; Yu, M. G.; Yoon, S. W.; Xiao, W.; Zoletnik, S.; the KSTAR Team

    2013-10-01

    foot induced small-sized high-frequency ELMs, leading to the mitigation of large ELMs. In addition to the ELM control experiments, various physics topics were explored focusing on ITER-relevant physics issues such as the alteration of toroidal rotation caused by both electron cyclotron resonance heating (ECRH) and externally applied 3D fields, and the observed rotation drop by ECRH in NB-heated plasmas was investigated in terms of either a reversal of the turbulence-driven residual stress due to the transition of ion temperature gradient to trapped electron mode turbulence or neoclassical toroidal viscosity (NTV) torque by the internal kink mode. The suppression of runaway electrons using massive gas injection of deuterium showed that runaway electrons were avoided only below 3 T in KSTAR. Operation in 2013 is expected to routinely exceed the n = 1 ideal MHD no-wall stability boundary in the long-pulse H-mode (⩾10 s) by applying real-time shaping control, enabling n = 1 resistive wall mode active control studies. In addition, intensive works for ELM mitigation, ELM dynamics, toroidal rotation changes by both ECRH and NTV variations, have begun in the present campaign, and will be investigated in more detail with profile measurements of different physical quantities by techniques such as electron cyclotron emission imaging, charge exchange spectroscopy, Thomson scattering and beam emission spectroscopy diagnostics.

  2. Wireless Channel Characterization in the 5 GHz Microwave Landing System Extension Band for Airport Surface Areas

    NASA Technical Reports Server (NTRS)

    Matolak, David W.

    2007-01-01

    In this project final report, entitled "Wireless Channel Characterization in the 5 GHz Microwave Landing System Extension Band for Airport Surface Areas," we provide a detailed description and model representation for the wireless channel in the airport surface environment in this band. In this executive summary, we review report contents, describe the achieved objectives and major findings, and highlight significant conclusions and recommendations.

  3. 3.5-GHz intra-burst repetition rate ultrafast Yb-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Akçaalan, Önder; Ilday, F. Ömer

    2016-05-01

    We report on an all-fiber Yb laser amplifier system with an intra-burst repetition rate of 3.5 GHz. The system is able to produce minimum of 15-ns long bursts containing approximately 50 pulses with a total energy of 215 μJ at a burst repetition rate of 1 kHz. The individual pulses are compressed down to the subpicosecond level. The seed signal from a 108 MHz fiber oscillator is converted to approximately 3.5 GHz by a multiplier consisting of six cascaded 50/50 couplers, and then amplified in ten stages. The highly cascaded amplification suppresses amplified spontaneous emission at low repetition rates. Nonlinear interactions between overlapping pulses within a burst is also discussed.

  4. Propagation Characteristics in an Underground Shopping Area for 5GHz-band Wireless Access Systems

    NASA Astrophysics Data System (ADS)

    Itokawa, Kiyohiko; Kita, Naoki; Sato, Akio; Matsue, Hideaki; Mori, Daisuke; Watanabe, Hironobu

    5-GHz band wireless access systems, such as the RLAN (Radio Local Area Network) system of IEEE802.11a, HiperLAN/2, HiSWANa and AWA, are developed and provide transmission rates over 20 Mbps for indoor use. Those 5-GHz access systems are expected to extend service areas from the office to the so-called “hot-spot" in public areas. Underground shopping malls are one of the anticipated service areas for such a nomadic wireless access service. Broadband propagation characteristics are required for radio zone design in an underground mall environment despite previous results obtained by narrow band measurements. This paper presents results of an experimental study on the propagation characteristics for broadband wireless access systems in an underground mall environment. First, broadband propagation path loss is measured and formulated considering human body shadowing. A ray trace simulation is used to clarify the basic propagation mechanism in such a closed environment. Next, a distance dependency of the delay spread during a crowded time period, rush hour, is found to be at most 65 nsec, which is under the permitted maximum value of the present 5-GHz systems. Finally, above propagation characteristics support the result of transmission test carried out by using AWA equipment.

  5. Diagnostics for first plasma and development plan on KSTAR

    SciTech Connect

    Lee, J. H.; Na, H. K.; Lee, S. G.; Bak, J. G.; Seo, D. C.; Seo, S. H.; Oh, S. T.; Ko, W. H.; Chung, J.; Nam, Y. U.; Lee, K. D.; Ka, E. M.; Oh, Y. K.; Kwon, M.; Jeong, S. H.

    2010-06-15

    The first plasma with target values of the plasma current and the pulse duration was finally achieved on June 13, 2008 in the Korea Superconducting Tokamak Advanced Research (KSTAR). The diagnostic systems played an important role in achieving successful first plasma operation for the KSTAR tokamak. The employed plasma diagnostic systems for the KSTAR first plasma including the magnetic diagnostics, millimeter-wave interferometer, inspection illuminator, H{sub {alpha}}, visible spectrometer, filterscope, and electron cyclotron emission (ECE) radiometer have provided the main plasma parameters, which are essential for the plasma generation, control, and physics understanding. Improvements to the first diagnostic systems and additional diagnostics including an x-ray imaging crystal spectrometer, reflectometer, ECE radiometer, resistive bolometer, and soft x-ray array are scheduled to be added for the next KSTAR experimental campaign in 2009.

  6. Design of practical alignment device in KSTAR Thomson diagnostic

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Lee, S. H.; Yamada, I.

    2016-11-01

    The precise alignment of the laser path and collection optics in Thomson scattering measurements is essential for accurately determining electron temperature and density in tokamak experiments. For the last five years, during the development stage, the KSTAR tokamak's Thomson diagnostic system has had alignment fibers installed in its optical collection modules, but these lacked a proper alignment detection system. In order to address these difficulties, an alignment verifying detection device between lasers and an object field of collection optics is developed. The alignment detection device utilizes two types of filters: a narrow laser band wavelength for laser, and a broad wavelength filter for Thomson scattering signal. Four such alignment detection devices have been successfully developed for the KSTAR Thomson scattering system in this year, and these will be tested in KSTAR experiments in 2016. In this paper, we present the newly developed alignment detection device for KSTAR's Thomson scattering diagnostics.

  7. Improved LHCD simulation model and implication for future experiments

    NASA Astrophysics Data System (ADS)

    Shiraiwa, S.; Wallace, G.; Baek, S.; Bonoli, P.; Faust, I.; Parker, R.; Labombard, B.; White, A.; Wukitch, S.

    2015-11-01

    The simulation model for LHCD using the raytracing/FokkerPlanck (GENRAY/CQL3D) code has been improved. Including realistic 2D SOL profiles resolves the discrepancy previously observed at high density (ne > 1 ×1020m-3). Impact of nonlinear interaction in front of the launcher is investigated. It is shown that the distortion of launch n| | spectrum is rather small (up to 10% of injected power). These simulation results suggest that improvement of current drive observed on Alcator C-Mod is indeed caused by realizing preferable SOL plasma profiles. Implication of these results to future experiments will be discussed. In order to minimize edge parasitic losses, realizing high single pass absorption and reducing prompt losses in front of launcher are both crucial. The advantage of LH launch from low field side (LFS) and high field side (HFS) is compared in this regards. A compact LH launcher suitable to test LH wave launch from HFS on a small scale device is designed and its plasma coupling characteristic will be presented. This work was performed on the Alcator C-Mod tokamak, a DoE Office of Science user facility, and is supported by USDoE awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  8. LHCD and ICRF heating experiments in H-mode plasmas on EAST

    SciTech Connect

    Zhang, X. J.; Zhao, Y. P.; Wan, B. N.; Ding, B. J.; Xu, G. S.; Gong, X. Z.; Li, J. G.; Lin, Y.; Wukitch, S.; Taylor, G.; Noterdaeme, J. M.; Braun, F.; Magne, R.; Litaudon, X.; Kumazawa, R.; Kasahara, H.; Collaboration: EAST Team

    2014-02-12

    An ICRF system with power up to 6.0 MW and a LHCD system up to 4MW have been applied for heating and current drive experiments on EAST. Intensive lithium wall coating was intensively used to reduce particle recycling and Hydrogen concentration in Deuterium plasma, which is needed for effective ICRF and LHCD power absorption in high density plasmas. Significant progress has been made with ICRF heating and LHW current drive for realizing the H-mode plasma operation in EAST. In 2010, H-mode was generated and sustained by LHCD alone, where lithium coating and gas puffing launcher mouth were applied to improve the LHCD power coupling and penetration into the core plasmas at high density of H-modes. During the last two experimental campaigns, ICRF Heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H Minority Heating (H-MH) mode, where electrons are predominantly heated by collisions with high energy minority ions. The H-MH mode gave the best plasma performance, and realized H-mode alone in 2012. Combination of ICRF and LHW power injection generated the H-mode plasmas with various ELMy characteristics. The first successful application of the ICRF Heating in the D (He3) plasma was also achieved. The progress on ICRF heating, LHCD experiments and their application in achieving H-mode operation from last two years will be discussed in this report.

  9. Note: Radio frequency surface impedance characterization system for superconducting samples at 7.5 GHz.

    PubMed

    Xiao, B P; Reece, C E; Phillips, H L; Geng, R L; Wang, H; Marhauser, F; Kelley, M J

    2011-05-01

    A radio frequency (RF) surface impedance characterization (SIC) system that uses a novel sapphire-loaded niobium cavity operating at 7.5 GHz has been developed as a tool to measure the RF surface impedance of flat superconducting material samples. The SIC system can presently make direct calorimetric RF surface impedance measurements on the central 0.8 cm(2) area of 5 cm diameter disk samples from 2 to 20 K exposed to RF magnetic fields up to 14 mT. To illustrate system utility, we present first measurement results for a bulk niobium sample. PMID:21639552

  10. VizieR Online Data Catalog: A 5-GHz Survey of Radio Sources (Altschuler 1986)

    NASA Astrophysics Data System (ADS)

    Altschuler, D. R.

    1999-11-01

    The results of a sensitive radio survey of about 0.04 sr of extragalactic sky in a narrow strip about declination = +33 deg are reported. The measurements were made with the NRAO 91-meter Green Bank telescope at a frequency of 4760 MHz. A catalogue of the 882 sources detected above a flux density of 15 mJy is given. The area surveyed is part of that covered earlier by the NRAO 5-GHz Survey of Faint Sources, Davis (1971). The results will allow an unbiased study of the variability characteristics of sources common to both surveys. (1 data file).

  11. Extraction and Analysis of Noise Parameters of On Wafer HEMTs up to 26.5 GHz

    SciTech Connect

    Caddemi, Alina; Crupi, Giovanni; Macchiarella, Alessio

    2009-04-23

    This paper presents a procedure for extracting the four noise parameters of on wafer scaled HEMTs based on AlGaAs/GaAs heterostructure. This procedure relies on 50-{omega} noise figure measurements up to 26.5 GHz by determining the equivalent temperatures associated to the intrinsic resistances of the small signal equivalent circuit. The non-quasi-static effect associated to the gate-drain resistance R{sub gd} is accounted for by the noise model. A good agreement between measured and simulated noise figure is obtained and scaling of the noise parameters is reported.

  12. Long pulse and steady state operation activities at KSTAR

    NASA Astrophysics Data System (ADS)

    Bae, Young-Soon; KSTAR Team; KAERI Collaboration; JAEA Collaboration; PPPL Collaboration; SNU Collaboration

    2014-10-01

    The mission of Korea Superconducting Tokamak Advanced Research (KSTAR) is to develop a steady state capable advanced tokamak (AT) operation. The original AT operation mode at KSTAR is a reversed shear scenario with the plasma current of 2 MA, the toroidal magnetic field of 3.5 T, βN of 5, safety factor q95 of 3.7. Recently, the stationary long pulse H-mode discharge is sustained for maximum pulse duration of 20 s using heating of 2.5-MW NBI and 0.7-MW, X3 170 GHz ECH with low density level ~ 0.3 × 1020/m3. The main activities of long pulse and steady state operation in KSTAR are the density feedback control, optimization of plasma shape and vertical control, real-time β control, and steady state capable heating upgrade. For the longer pulse H-mode discharge at the increased plasma current upcoming KSTAR campaign, there have been improvements in plasma control system and upgraded heating systems. Meanwhile, steady state operation scenario in KSTAR next 4-year is being investigated using time-dependent integrated transport simulation code with possible heating upgrade-schemes. The promising steady state scenario near future is a reversed shear using a new 4 MW off-axis neutral beam injector for broad pressure profile peaked at off-axis, and using ECH for local current profile control aiming at βN > 3 with Ip ~ 1 MA. This paper present activities and plan for steady state operation in KSTAR as well as the long pulse H-mode discharge results in the recent KSTAR campaign.

  13. Reconfigurable antenna options for 2.45/5 GHz wireless body area networks in healthcare applications.

    PubMed

    Abbas, Syed Muzahir; Ranga, Yogesh; Esselle, Karu P

    2015-01-01

    This paper presents electronically reconfigurable antenna options in healthcare applications. They are suitable for wireless body area network devices operating in the industrial, scientific, and medical (ISM) band at 2.45 GHz and IEEE 802.11 Wireless Local Area Network (WLAN) band at 5 GHz (5.15-5.35 GHz, 5.25-5.35 GHz). Two types of antennas are investigated: Antenna-I has a full ground plane and Antenna-II has a partial ground plane. The proposed antennas provide ISM operation in one mode while in another mode they support 5 GHz WLAN band. Their performance is assessed for body centric wireless communication using a simplified human body model. Antenna sensitivity to the gap between the antenna and the human body is investigated for both modes of each antenna. The proposed antennas exhibit a wide radiation pattern along the body surface to provide wide coverage and their small width (14 mm) makes them suitable for on-body communication in healthcare applications. PMID:26737528

  14. Design and realization of a planar ultrawideband antenna with notch band at 3.5 GHz.

    PubMed

    Azim, Rezaul; Islam, Mohammad Tariqul; Misran, Norbahiah; Yatim, Baharudin; Arshad, Haslina

    2014-01-01

    A small antenna with single notch band at 3.5 GHz is designed for ultrawideband (UWB) communication applications. The fabricated antenna comprises a radiating monopole element and a perfectly conducting ground plane with a wide slot. To achieve a notch band at 3.5 GHz, a parasitic element has been inserted in the same plane of the substrate along with the radiating patch. Experimental results shows that, by properly adjusting the position of the parasitic element, the designed antenna can achieve an ultrawide operating band of 3.04 to 11 GHz with a notched band operating at 3.31-3.84 GHz. Moreover, the proposed antenna achieved a good gain except at the notched band and exhibits symmetric radiation patterns throughout the operating band. The prototype of the proposed antenna possesses a very compact size and uses simple structures to attain the stop band characteristic with an aim to lessen the interference between UWB and worldwide interoperability for microwave access (WiMAX) band. PMID:25133245

  15. Design and realization of a planar ultrawideband antenna with notch band at 3.5 GHz.

    PubMed

    Azim, Rezaul; Islam, Mohammad Tariqul; Misran, Norbahiah; Yatim, Baharudin; Arshad, Haslina

    2014-01-01

    A small antenna with single notch band at 3.5 GHz is designed for ultrawideband (UWB) communication applications. The fabricated antenna comprises a radiating monopole element and a perfectly conducting ground plane with a wide slot. To achieve a notch band at 3.5 GHz, a parasitic element has been inserted in the same plane of the substrate along with the radiating patch. Experimental results shows that, by properly adjusting the position of the parasitic element, the designed antenna can achieve an ultrawide operating band of 3.04 to 11 GHz with a notched band operating at 3.31-3.84 GHz. Moreover, the proposed antenna achieved a good gain except at the notched band and exhibits symmetric radiation patterns throughout the operating band. The prototype of the proposed antenna possesses a very compact size and uses simple structures to attain the stop band characteristic with an aim to lessen the interference between UWB and worldwide interoperability for microwave access (WiMAX) band.

  16. Reconfigurable antenna options for 2.45/5 GHz wireless body area networks in healthcare applications.

    PubMed

    Abbas, Syed Muzahir; Ranga, Yogesh; Esselle, Karu P

    2015-01-01

    This paper presents electronically reconfigurable antenna options in healthcare applications. They are suitable for wireless body area network devices operating in the industrial, scientific, and medical (ISM) band at 2.45 GHz and IEEE 802.11 Wireless Local Area Network (WLAN) band at 5 GHz (5.15-5.35 GHz, 5.25-5.35 GHz). Two types of antennas are investigated: Antenna-I has a full ground plane and Antenna-II has a partial ground plane. The proposed antennas provide ISM operation in one mode while in another mode they support 5 GHz WLAN band. Their performance is assessed for body centric wireless communication using a simplified human body model. Antenna sensitivity to the gap between the antenna and the human body is investigated for both modes of each antenna. The proposed antennas exhibit a wide radiation pattern along the body surface to provide wide coverage and their small width (14 mm) makes them suitable for on-body communication in healthcare applications.

  17. Experimental characterization and modeling of non-linear coupling of the LHCD power on Tore Supra

    NASA Astrophysics Data System (ADS)

    Preynas, M.; Goniche, M.; Hillairet, J.; Litaudon, X.; Ekedahl, A.

    2014-02-01

    To achieve steady state operation on future tokamaks, in particular on ITER, the unique capability of a LHCD system to efficiently drive off-axis non-inductive current is needed. In this context, it is of prime importance to study and master the coupling of LH wave to the core plasma at high power density (tens of MW/m2). In some specific conditions, deleterious effects on the LHCD coupling are sometimes observed on Tore Supra. At high power the waves may modify the edge parameters that change the wave coupling properties in a non-linear manner. In this way, dedicated LHCD experiments have been performed using the LHCD system of Tore Supra, composed of two different conceptual designs of launcher: the Fully Active Multijunction (FAM) and the new Passive Active Multijunction (PAM) antennas. A nonlinear interaction between the electron density and the electric field has been characterized in a thin plasma layer in front of the two LHCD antennas. The resulting dependence of the power reflection coefficient with the LHCD power, leading occasionally to trips in the output power, is not predicted by the standard linear theory of the LH wave coupling. Therefore, it is important to investigate and understand the possible origin of such non-linear effects in order to avoid their possible deleterious consequences. The PICCOLO-2D code, which self-consistently treats the wave propagation in the antenna vicinity and its interaction with the local edge plasma density, is used to simulate Tore Supra discharges. The simulation reproduces very well the occurrence of a non-linear behavior in the coupling observed in the LHCD experiments. The important differences and trends between the FAM and the PAM antennas, especially a larger increase in RC for the FAM, are also reproduced by the PICCOLO-2D simulation. The working hypothesis of the contribution of the ponderomotive effect in the non-linear observations of LHCD coupling is therefore validated through this comprehensive modeling

  18. Design of the klystron filament power supply control system for EAST LHCD

    NASA Astrophysics Data System (ADS)

    Wu, Zege; Wang, Mao; Hu, Huaichuan; Ma, Wendong; Zhou, Taian; Zhou, Faxin; Liu, Fukun; Shan, Jiafang

    2016-09-01

    A filament is a critical component of the klystron used to heat the cathode. There are totally 44 klystrons in experimental advanced superconducting tokamak (EAST) lower hybrid current drive (LHCD) systems. All klystron filaments are powered by AC power suppliers through isolated transformers. In order to achieve better klystron preheat, a klystron filament power supply control system is designed to obtain the automatic control of all filament power suppliers. Klystron filament current is measured by PLC and the interlock between filament current and klystron high voltage system is also implemented. This design has already been deployed in two LHCD systems and proves feasible completely.

  19. Experimental characterization and modeling of non-linear coupling of the LHCD power on Tore Supra

    SciTech Connect

    Preynas, M.; Goniche, M.; Hillairet, J.; Litaudon, X.; Ekedahl, A.

    2014-02-12

    To achieve steady state operation on future tokamaks, in particular on ITER, the unique capability of a LHCD system to efficiently drive off-axis non-inductive current is needed. In this context, it is of prime importance to study and master the coupling of LH wave to the core plasma at high power density (tens of MW/m{sup 2}). In some specific conditions, deleterious effects on the LHCD coupling are sometimes observed on Tore Supra. At high power the waves may modify the edge parameters that change the wave coupling properties in a non-linear manner. In this way, dedicated LHCD experiments have been performed using the LHCD system of Tore Supra, composed of two different conceptual designs of launcher: the Fully Active Multijunction (FAM) and the new Passive Active Multijunction (PAM) antennas. A nonlinear interaction between the electron density and the electric field has been characterized in a thin plasma layer in front of the two LHCD antennas. The resulting dependence of the power reflection coefficient with the LHCD power, leading occasionally to trips in the output power, is not predicted by the standard linear theory of the LH wave coupling. Therefore, it is important to investigate and understand the possible origin of such non-linear effects in order to avoid their possible deleterious consequences. The PICCOLO-2D code, which self-consistently treats the wave propagation in the antenna vicinity and its interaction with the local edge plasma density, is used to simulate Tore Supra discharges. The simulation reproduces very well the occurrence of a non-linear behavior in the coupling observed in the LHCD experiments. The important differences and trends between the FAM and the PAM antennas, especially a larger increase in RC for the FAM, are also reproduced by the PICCOLO-2D simulation. The working hypothesis of the contribution of the ponderomotive effect in the non-linear observations of LHCD coupling is therefore validated through this comprehensive

  20. Present Status of the KSTAR Superconducting Magnet System Development

    NASA Astrophysics Data System (ADS)

    Kim, Keeman; H, K. Park; K, R. Park; B, S. Lim; S, I. Lee; M, K. Kim; Y, Chu; W, H. Chung; S, H. Baek; J Y, Choi; H, Yonekawa; A, Chertovskikh; Y, B. Chang; J, S. Kim; C, S. Kim; D, J. Kim; N, H. Song; K, P. Kim; Y, J. Song; I, S. Woo; W, S. Han; D, K. Lee; Y, K. Oh; K, W. Cho; J, S. Park; G, S. Lee; H, J. Lee; T, K. Ko; S, J. Lee

    2004-10-01

    The mission of Korea Superconducting Tokamak Advanced Research (KSTAR) project is to develop an advanced steady-state superconducting tokamak for establishing a scientific and technological basis for an attractive fusion reactor. Because one of the KSTAR mission is to achieve a steady-state operation, the use of superconducting coils is an obvious choice for the magnet system. The KSTAR superconducting magnet system consists of 16 Toroidal Field (TF) coils and 14 Poloidal Field (PF) coils. Internally-cooled Cable-In-Conduit Conductors (CICC) are put into use in both the TF and PF coil systems. The TF coil system provides a field of 3.5 T at the plasma center and the PF coil system is able to provide a flux swing of 17 V-sec. The major achievement in KSTAR magnet-system development includes the development of CICC, the development of a full-size TF model coil, the development of a coil system for background magnetic-field generation, the construction of a large-scale superconducting magnet and CICC test facility. TF and PF coils are in the stage of fabrication to pave the way for the scheduled completion of KSTAR by the end of 2006.

  1. A measurement of the cosmic microwave background temperature at 7.5 GHz

    NASA Technical Reports Server (NTRS)

    Levin, S.; Bensadoun, M.; Bersanelli, M.; De Amici, G.; Kogut, A.; Limon, M.; Smoot, G.

    1992-01-01

    The temperature of the cosmic microwave background (CMB) radiation at a frequency of 7.5 GHz (4 cm wavelength) is measured, obtaining a brightness temperature of T(CMB) = 2.70 +/- 0.08 K (68 percent confidence level). The measurement was made from a site near the geographical South Pole during the austral spring of 1989 and was part of an international collaboration to measure the CMB spectrum at low frequencies with a variety of radiometers from several different sites. This recent result is in agreement with the 1988 measurement at the same frequency, which was made from a different site with significantly different systematic errors. The combined result of the 1988 and 1989 measurements is 2.64 +/- 0.06 K.

  2. PRECISE ABSOLUTE ASTROMETRY FROM THE VLBA IMAGING AND POLARIMETRY SURVEY AT 5 GHz

    SciTech Connect

    Petrov, L.

    2011-09-15

    We present accurate positions for 857 sources derived from the astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline Array imaging and polarimetry survey at 5 GHz (VIPS). Among the observed sources, positions of 430 objects were not previously determined at milliarcsecond-level accuracy. For 95% of the sources the uncertainty of their positions ranges from 0.3 to 0.9 mas, with a median value of 0.5 mas. This estimate of accuracy is substantiated by the comparison of positions of 386 sources that were previously observed in astrometric programs simultaneously at 2.3/8.6 GHz. Surprisingly, the ionosphere contribution to group delay was adequately modeled with the use of the total electron content maps derived from GPS observations and only marginally affected estimates of source coordinates.

  3. Characterization of timing jitter in a 5 GHz quantum dot passively mode-locked laser.

    PubMed

    Lin, Chang-Yi; Grillot, Frederic; Li, Yan; Raghunathan, Ravi; Lester, Luke F

    2010-10-11

    The timing jitter performance of a 5 GHz quantum dot passively mode-locked laser is investigated at different harmonics in the RF spectrum. The necessity of measuring the phase noise at relatively large harmonic numbers is motivated experimentally in the context of determining the corner frequency, its correlation to the RF linewidth, and the related white noise plateau level. The single-sideband phase noise with an integrated timing jitter of 211 fs (4-80 MHz) is reported. An all-microwave technique has been used to determine a pulse-to-pulse rms timing jitter of 96 fs/cycle. This low timing jitter value makes the chip-scale quantum dot mode-locked laser an attractive source for low noise applications such as optical clocking and sampling. PMID:20941093

  4. Noise in waveguide between 18 GHz and 26.5 GHz

    NASA Astrophysics Data System (ADS)

    Allal, D.

    2016-01-01

    This report summarises the results of the Key Comparison CCEM.RF-K22.W on noise temperature, performed between October 2007 and February 2011. In this comparison, the available noise temperature of three noise sources was determined by six National Metrology Institutes (NMIs) in the frequency range from 18 GHz to 26.5 GHz. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  5. A compact 5.5 GHz band-rejected UWB antenna using complementary split ring resonators.

    PubMed

    Islam, M M; Faruque, M R I; Islam, M T

    2014-01-01

    A band-removal property employing microwave frequencies using complementary split ring resonators (CSRRs) is applied to design a compact UWB antenna wishing for the rejection of some frequency band, which is meanwhile exercised by the existing wireless applications. The reported antenna comprises optimization of a circular radiating patch, in which slotted complementary SRRs are implanted. It is printed on low dielectric FR4 substrate material fed by a partial ground plane and a microstrip line. Validated results exhibit that the reported antenna shows a wide bandwidth covering from 3.45 to more than 12 GHz, with a compact dimension of 22 × 26 mm(2), and VSWR < 2, observing band elimination of 5.5 GHz WLAN band. PMID:24971379

  6. Dynamical back-action at 5.5 GHz in a corrugated optomechanical beam

    SciTech Connect

    Navarro-Urrios, D.; Gomis-Bresco, J.; Alzina, F.; El-Jallal, S.; Oudich, M.; Pennec, Y.; Djafari-Rouhani, B.; Pitanti, A.; Capuj, N.; Tredicucci, A.; Griol, A.; Martínez, A.; Sotomayor Torres, C. M.

    2014-12-15

    We report on the optomechanical properties of a breathing mechanical mode oscillating at 5.5 GHz in a 1D corrugated Si nanobeam. This mode has an experimental single-particle optomechanical coupling rate of |g{sub o,OM}| = 1.8 MHz (|g{sub o,OM}|/2π = 0.3 MHz) and shows strong dynamical back-action effects at room temperature. The geometrical flexibility of the unit-cell would lend itself to further engineering of the cavity region to localize the mode within the full phononic band-gap present at 4 GHz while keeping high g{sub o,OM} values. This would lead to longer lifetimes at cryogenic temperatures, due to the suppression of acoustic leakage.

  7. Edge profile measurements using Thomson scattering on the KSTAR tokamak.

    PubMed

    Lee, J H; Oh, S; Lee, W R; Ko, W H; Kim, K P; Lee, K D; Jeon, Y M; Yoon, S W; Cho, K W; Narihara, K; Yamada, I; Yasuhara, R; Hatae, T; Yatsuka, E; Ono, T; Hong, J H

    2014-11-01

    In the KSTAR Tokamak, a "Tangential Thomson Scattering" (TTS) diagnostic system has been designed and installed to measure electron density and temperature profiles. In the edge system, TTS has 12 optical fiber bundles to measure the edge profiles with 10-15 mm spatial resolution. These 12 optical fibers and their spatial resolution are not enough to measure the pedestal width with a high accuracy but allow observations of L-H transition or H-L transitions at the edge. For these measurements, the prototype ITER edge Thomson Nd:YAG laser system manufactured by JAEA in Japan is installed. In this paper, the KSTAR TTS system is briefly described and some TTS edge profiles are presented and compared against the KSTAR Charge Exchange Spectroscopy and other diagnostics. The future upgrade plan of the system is also discussed in this paper.

  8. Integration of LHCD system with SST1 machine and its high power rf performance in vacuum

    NASA Astrophysics Data System (ADS)

    Sharma, P. K.; Ambulkar, K. K.; Dalakoti, S.; Parmar, P. R.; Virani, C. G.; Thakur, A. L.

    2014-02-01

    A 2.0 MW CW lower hybrid current drive (LHCD) system based on 3.7 GHz klystron sources, is in advanced stage of commissioning, which would drive and sustain plasma current, non-inductively, in superconducting steadystate tokamak (SST1) for long pulse operation. Four klystrons, each rated for 0.5 MW CW rf power, delivers 2.0 MW of rf power to four layer of the LHCD system, which finally feeds the rf power to grill antenna. The antenna system along with vacuum window and vacuum transmission line is successfully integrated on the machine. Its vacuum and pressurization compatibility has been successfully established. To validate the high power performance of LHCD system for SST1 machine, stage-wise commissioning of LHCD system in staggered manner is planned. It has been envisaged that LHCD power may be gradually increased initially, since full power may not be required during the initial phases of SST1 plasma operation. Also if the system is integrated in steps or in phases, then integration issues, as well as high power operational issues, if any, can be addressed, attended and handled in a simpler way before integrating all the layers to the grill antenna. To begin with, one klystron is connected to one layer, out of four layers, which energizes a quarter of the grill antenna. Gradually, the rf power and its pulse length is increased to validate high power performance of the system. Arcing and reflections are observed as rf power is gradually increased. The problems are analysed and after taking appropriate remedial action the system performance is improved for operation up to 160kW. Several trains of short pulses are launched in SST1 vacuum vessel for rf conditioning of the LHCD system. Normally, reflections are high when power is launched in vacuum; therefore the pulse length is restricted up to 100 milliseconds. The high power performance of this layer, connected with grill antenna is validated by launching high power microwaves in vacuum vessel of SST1 machine

  9. Development of prototype polychromator system for KSTAR Thomson scattering diagnostic

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Lee, S. H.; Son, S. H.; Ko, W. H.; Seo, D. C.; Yamada, I.; Her, K. H.; Jeon, J. S.; Bog, M. G.

    2015-12-01

    A polychromator is widely used by the Thomson scattering system for measuring the electron temperature and density. This type of spectrometer includes optic elements such as band-pass filters, focusing lens, collimating lens, and avalanche photodiodes (APDs). The characteristics of band-pass filters in the polychromator are determined by the measuring range of the Thomson system. KSTAR edge polychromators were developed by co-works at NIFS in Japan, and the KSTAR core polychromators were developed by NFRI in Korea. The power supply system of these polychromators is connected only to one power supply module and can manually control the APD's voltage at the front side of the power supply by using a potentiometer. In this paper, a prototype polychromator is introduced at the KSTAR. The prototype polychromator system has a built-in power supply unit that includes high voltage for the APD and ± 5 V for an op-amp IC. The high voltage for the APD is finely controlled and monitored using a PC with the LabView software. One out of the six band pass-filters has a center wavelength of 523.5 nm with 2-nm bandwidth, which can measure Zeff, and the other five band-pass filters can simultaneously measure the Thomson signal. In addition, we will show the test result of this prototype polychromator system during the KSTAR experiment campaign (2015).

  10. Operation Results of the Kstar Helium Refrigeration System

    NASA Astrophysics Data System (ADS)

    Chang, H.-S.; Fauve, E.; Park, D.-S.; Joo, J.-J.; Moon, K.-M.; Cho, K.-W.; Na, H. K.; Kwon, M.; Yang, S.-H.; Gistau-Baguer, G.

    2010-04-01

    The "first plasma" (100 kA of controllable plasma current for 100 ms) of KSTAR has been successfully generated in July 2008. The major outstanding feature of KSTAR compared to most other Tokamaks is that all the magnet coils are superconducting (SC), which enables higher plasma current values for a longer time duration when the nominal operation status has been reached. However, to establish the operating condition for the SC coils, other cold components, such as thermal shields, coil-supporting structures, SC buslines, and current leads also must be maintained at proper cryogenic temperature levels. A helium refrigeration system (HRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K has been installed for such purposes and successfully commissioned. In this proceeding, we will report on the operation results of the HRS during the first plasma campaign of KSTAR. Using the HRS, the 300-ton cold mass of KSTAR was cooled down from ambient to the operating temperature levels of each cold component. Stable and steady cryogenic conditions, proper for the generation of the "first plasma" have been maintained for three months, after which, all of the cold mass was warmed up again to ambient temperature.

  11. A sensitive 1.5 GHz radio survey around the north ecliptic pole

    NASA Technical Reports Server (NTRS)

    Kollgaard, Ronald I.; Brinkmann, Wolfgang; Chester, Margaret Mcmath; Feigelson, Eric D.; Hertz, Paul; Reich, Patricia; Wielebinski, Richard

    1994-01-01

    A 29.3 sq deg region surrounding the north ecliptic pole (NEP; alpha = 18h00m, delta = +66 deg 30 min) was mapped with the Very Large Array at 1.5 GHz to support the deepest portion of the ROSAT all-sky soft X-ray survey. The resulting VLA-NEP survey catalog contains 2435 radio sources with flux densities in the range of 0.3-1000 mJy, including over 200 fainter than 1 mJy. The 28 fields of the inner 1.5 deg have noise levels sigma approximately equals 60 mu-Jy, and the 85 fields centered between 1.5 and 3.0 deg from the NEP have sigma approximately equals 120 mu-Jy. The typical spatial resolution is 20 sec HPBW, and most positions are accurate to less than 2 sec. Approximately 6% of the sources are found to be extended with size greater than 30 sec. We have compared the VLA-NEP catalog with four other radio catalogs made at lower resolution, as well as with the NASA Extragalactic Database and find counterparts for approximately 18% of the VLA-NEP objects. The normalized, differential radio source count is in agreement with previous studies. Between 1 and 150 mJy the slope of the log N-log S relation is 0.68 +/- 0.03. The catalog and related tables are available electronically.

  12. Limits on Arcminute-Scale Cosmic Microwave Background Anisotropy at 28.5 GHz

    NASA Technical Reports Server (NTRS)

    Holzapfel, W. L.; Carlstrom, J. E.; Grego, L.; Holder, G.; Joy, M.; Reese, E. D.

    2000-01-01

    We have used the Berkeley-Illinois-Maryland Association (BIMA) millimeter array outfitted with sensitive centimeter-wave receivers to search for cosmic microwave background (CMB) anisotropies on arcminute scales. The interferometer was placed in a compact configuration that produces high brightness sensitivity, while providing discrimination against point sources. Operating at a frequency of 28.5 GHz, the FWHM primary beam of the instrument is approximately 6'.6. We have made sensitive images of seven fields, four of which where chosen specifically to have low infrared dust contrast and to be free of bright radio sources. Additional observations with the Owens Valley Radio Observatory (OVRO) millimeter array were used to assist in the location and removal of radio point sources. Applying a Bayesian analysis to the raw visibility data, we place limits on CMB anisotropy flat-band power of Q(sub flat) = 5.6(sub -5.6)(exp 3.0) microK and Q(sub flat) < 14.1 microK at 68% and 95% confidence, respectively. The sensitivity of this experiment to flat-band power peaks at a multipole of I = 5470, which corresponds to an angular scale of approximately 2'. The most likely value of Q(sub flat) is similar to the level of the expected secondary anisotropies.

  13. Measurements of LHCD current profile and efficiency for simulation validation on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Mumgaard, Robert T.

    2014-10-01

    Lower hybrid current drive (LHCD) is an effective tool to significantly modify the magnetic equilibrium by driving off-axis, non-inductive current. On Alcator C-Mod, an upgraded Motional Stark Effect (MSE) diagnostic enables the current profile to be accurately reconstructed during plasmas with strong LHCD and a hard X-ray camera measures the fast electron Bremsstrahlung profile. LHCD is applied for >4 current relaxation times, producing fully-relaxed magnetic equilibria in plasmas with non-inductive current fraction up to unity at currents up to 1.0 MA. C-Mod has developed an extensive database of LHCD performance, spanning a wide range in plasma current, launched n||, LHCD power, Te and plasma density. This dataset provides a unique platform for validation of LHCD current drive simulations with the plasma shape, density, field and LH frequency range envisioned for ITER and future reactors. In these conditions the measured current drive efficiencies are similar to that assumed for ITER with values up to 0.4*1020A/Wm2 despite being in a weak single-pass absorption regime. The driven current is observed to be off-axis, broadening the current profile, raising q0 above 1, suppressing sawteeth, decreasing/reversing the magnetic shear and sometimes destabilizing MHD modes and/or triggering internal transport barriers. Measurements indicate increased efficiency at increased temperature and plasma current but with a complicated dependence on launched n||. The MSE-constrained reconstructions show a loss in current drive efficiency as the plasma density is increased above =1.0×1020 m-3 consistent with previous observations of a precipitous drop in hard x-ray emission. Additionally, the measured driven current profile moves radially outward as the density is increased. Ray tracing simulations using GENRAY-CQL3D qualitatively reproduce these trends showing the rays make many passes through the plasma at high density and predicting a narrower current and HXR profile

  14. Impurity Radiation From The LHCD Launcher During Operation In JET And Investigation Of Launcher Damage

    NASA Astrophysics Data System (ADS)

    Kirov, K. K.; Mailloux, J.; Lhcd Team; Jet Efda Contributors

    2005-09-01

    In this study, the most likely causes of the enhanced radiation in front of the LHCD launcher are investigated: fast ions from the warm plasma, fast electrons parasitically accelerated in front of the grill and arcs. Evidence for the presence of each of these mechanisms is discussed. The experimental conditions favouring the appearance of these phenomena and their impact on the launcher have also been highlighted.

  15. FOREGROUND PREDICTIONS FOR THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM FROM MEASUREMENTS OF FAINT INVERTED RADIO SOURCES AT 5 GHz

    SciTech Connect

    Schneider, Michael D.; Becker, Robert H.; De Vries, Willem; White, Richard L.

    2012-05-10

    We present measurements of a population of matched radio sources at 1.4 and 5 GHz down to a flux limit of 1.5 mJy in 7 deg{sup 2} of the NOAO Deep Field South. We find a significant fraction of sources with inverted spectral indices that all have 1.4 GHz fluxes less than 10 mJy and are therefore too faint to have been detected and included in previous radio source count models that are matched at multiple frequencies. Combined with the matched source population at 1.4 and 5 GHz in 1 deg{sup -2} in the ATESP survey, we update models for the 5 GHz differential number counts and distributions of spectral indices in 5 GHz flux bins that can be used to estimate the unresolved point source contribution to the cosmic microwave background temperature anisotropies. We find a shallower logarithmic slope in the 5 GHz differential counts than in previously published models for fluxes {approx}< 100 mJy as well as larger fractions of inverted spectral indices at these fluxes. Because the Planck flux limit for resolved sources is larger than 100 mJy in all channels, our modified number counts yield at most a 10% change in the predicted Poisson contribution to the Planck temperature power spectrum. For a flux cut of 5 mJy with the South Pole Telescope and a flux cut of 20 mJy with the Atacama Cosmology Telescope, we predict a {approx}30% and {approx}10% increase, respectively, in the radio source Poisson power in the lowest frequency channels of each experiment relative to that predicted by previous models.

  16. Runaway Electron Suppression by ECRH and RMP in KSTAR

    NASA Astrophysics Data System (ADS)

    C. England, A.; Y. Chen, Z.; C. Seo, D.; Chung, J.; S. Leev, Y.; W. Yoo, J.; C. Kim, W.; S. Bae, Y.; M. Jeonv, Y.; G. Kwak, J.; M., Kwon; the Kstar Team

    2013-02-01

    We have observed reduction of the runaway electron synchrotron radiation, hard X-ray (HXR) intensity, and HXR energy after applying 110 GHz 2nd harmonic electron cyclotron resonant heating (ECRH) during runaway electron (RE) discharges at low density with startup runaway electrons. However, we did not see a significant reduction of X-rays from 170 GHz 2nd harmonic ECRH at a higher field. A recently installed IR TV camera was used to observe the forward cone of synchrotron radiation from high energy REs in KSTAR. We have observed changes to the synchrotron images and reduction of the HXR by application of resonant magnetic perturbations (RMP) from in-vessel control coils (IVCC) installed inside KSTAR in the n = 1 configuration.

  17. Triton burnup measurements in KSTAR using a neutron activation system

    NASA Astrophysics Data System (ADS)

    Jo, Jungmin; Cheon, MunSeong; Kim, Jun Young; Rhee, T.; Kim, Junghee; Shi, Yue-Jiang; Isobe, M.; Ogawa, K.; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-11-01

    Measurements of the time-integrated triton burnup for deuterium plasma in Korea Superconducting Tokamak Advanced Research (KSTAR) have been performed following the simultaneous detection of the d-d and d-t neutrons. The d-d neutrons were measured using a 3He proportional counter, fission chamber, and activated indium sample, whereas the d-t neutrons were detected using activated silicon and copper samples. The triton burnup ratio from KSTAR discharges is found to be in the range 0.01%-0.50% depending on the plasma conditions. The measured burnup ratio is compared with the prompt loss fraction of tritons calculated with the Lorentz orbit code and the classical slowing-down time. The burnup ratio is found to increase as plasma current and classical slowing-down time increase.

  18. MSE commissioning and other major diagnostic updates on KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, Jinseok; Kstar Team

    2015-11-01

    The motional Stark effect (MSE) diagnostic based on the photoelastic-modulator (PEM) approach has been commissioned for the Korea Superconducting Tokamak Advanced Research (KSTAR). The 25-channel MSE system with the polarization-preserving front optics and precise tilt-tuning narrow bandpass filters provides the spatial resolution less than 1 cm in most of the plasma cross section and about 10 millisecond of time resolution. The polarization response curves with the daily Faraday rotation correction provides reliable pitch angle profiles for the KSTAR discharges with the MSE-optimized energy combination in the three-ion-source neutral beam injection. Some major diagnostic advances such as the poloidal charge exchange spectroscopy, the improved Thomson-scatting system, and the divertor infrared TV are reported as well. Work supported by the Ministry of Science, ICT and Future Planning, Korea.

  19. Predictions of the poloidal asymmetries and transport frequencies in KSTAR

    SciTech Connect

    Bae, C. Lee, S. G.; Terzolo, L.; Stacey, W. M.

    2014-01-15

    The extended neoclassical rotation theory formulated in Miller flux surface geometry enables unprecedented neoclassical calculations of the poloidal asymmetries in density, rotation velocities, electrostatic potential along the flux surfaces, and of the inertial (Reynolds stress) and gyroviscous transport frequencies, which are strong functions of these asymmetries. This paper presents such calculations of the poloidal asymmetries and non-negligible inertial and gyroviscous transport frequencies in two KSTAR (Korea Superconducting Tokamak Advanced Research) [Kwon et al., Nucl. Fusion 51, 094006 (2011)] Neutral Beam Injection H-mode discharges. The in-out asymmetries in the velocities are an order of magnitude larger than their up-down asymmetries. The magnitudes of the predicted inertial and gyroviscous transport frequencies depend on the magnitudes of the density and velocity asymmetries. The neoclassically predicted density asymmetries are shown to correspond with the reported measurements in tokamaks and the predicted carbon toroidal velocities agree very well with the measurements in KSTAR.

  20. First neutral beam injection experiments on KSTAR tokamaka)

    NASA Astrophysics Data System (ADS)

    Jeong, S. H.; Chang, D. H.; Kim, T. S.; In, S. R.; Lee, K. W.; Jin, J. T.; Chang, D. S.; Oh, B. H.; Bae, Y. S.; Kim, J. S.; Park, H. T.; Watanabe, K.; Inoue, T.; Kashiwagi, M.; Dairaku, M.; Tobari, H.; Hanada, M.

    2012-02-01

    The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak was partially completed in 2010 with only 1/3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1-1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D+:D2+:D3+ = 75:20:5 at beam current density of 85 mA/cm2. The arc efficiency is more than 1.0 A/kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the Ti and Te profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.

  1. First neutral beam injection experiments on KSTAR tokamak.

    PubMed

    Jeong, S H; Chang, D H; Kim, T S; In, S R; Lee, K W; Jin, J T; Chang, D S; Oh, B H; Bae, Y S; Kim, J S; Park, H T; Watanabe, K; Inoue, T; Kashiwagi, M; Dairaku, M; Tobari, H; Hanada, M

    2012-02-01

    The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak was partially completed in 2010 with only 1∕3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1-1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D(+):D(2)(+):D(3)(+) = 75:20:5 at beam current density of 85 mA/cm(2). The arc efficiency is more than 1.0 A∕kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the T(i) and T(e) profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.

  2. Instrumentation for a multichord motional Stark effect diagnostic in KSTAR

    NASA Astrophysics Data System (ADS)

    Chung, J.; Ko, J.; De Bock, M. F. M.; Jaspers, R. J. E.

    2014-11-01

    The motional Stark effect (MSE) diagnostic is used to measure the radial magnetic pitch angle profile in neutral beam heated plasmas. This information is used to calculate the safety factor, q, with magnetic equilibrium reconstruction codes such as EFIT. The MSE diagnostic is important during active shaping of the q profile to optimize confinement and stability, and it has become a key diagnostic in high performance tokamaks. A multichord photo-elastic modulator (PEM) based MSE system is being developed for a real-time plasma current profile control in Korea Superconducting Tokamak Advanced Research (KSTAR). The PEM-based approach is a standard method that measures the polarization direction of a single Stark line with narrow tunable bandpass filters. A tangential view of the heating beam provides good spatial resolution of 1-3 cm, which provides an opportunity to install 25 spatial channels spanning the major radius from 1.74 m to 2.84 m. Application of real-time control is a long-term technical goal after commissioning the diagnostic in KSTAR, which is expected in 2015. In this paper, we describe the design of this newly-constructed multichord MSE diagnostic in KSTAR.

  3. First results of LHCD experiments with 4.6 GHz system toward steady-state plasma in EAST

    NASA Astrophysics Data System (ADS)

    Liu, F. K.; Ding, B. J.; Li, J. G.; Wan, B. N.; Shan, J. F.; Wang, M.; Liu, L.; Zhao, L. M.; Li, M. H.; Li, Y. C.; Yang, Y.; Wu, Z. G.; Feng, J. Q.; Hu, H. C.; Jia, H.; Huang, Y. Y.; Wei, W.; Cheng, M.; Xu, L.; Zang, Q.; Lyu, B.; Lin, S. Y.; Duan, Y. M.; Wu, J. H.; Peysson, Y.; Decker, J.; Hillairet, J.; Ekedahl, A.; Luo, Z. P.; Qian, J. P.; Shen, B.; Gong, X. Z.; Hu, L. Q.; the EAST Team

    2015-11-01

    A 4.6 GHz lower-hybrid current drive (LHCD) system has been firstly commissioned in EAST in the 2014 campaign. The first LHCD results with 4.6 GHz show that LHW can be coupled to plasma with a low reflection coefficient, drive plasma current and plasma rotation, modify the plasma current profile, and heat plasma effectively. By means of configuration optimization and local gas puffing near the LHW antenna, good LHW-plasma coupling with a reflection coefficient less than 5% is obtained. The maximum LHW power coupled to plasma is up to 3.5 MW. The current drive (CD) efficiency is up to 1.1  ×  1019 A m-2 W-1 and the central electron temperature is above 4 keV, suggesting that LH power could be mainly deposited in the core region, which is in agreement with code simulation. Experiments show that the current profile is effectively modified and toroidal rotation in the co-current direction is driven by the LHCD. Also, the CD efficiency and current profile depend on the launched wave spectrum, suggesting the possibility of controlling the current profile by changing the phase difference. Repeatable H-mode plasma is obtained by either the 4.6 GHz LHCD system alone, or together with a 2.45 GHz LHCD system, the NBI (neutral beam injection) system. The different ELM features of H-mode between the different heating methods are under investigation.

  4. The LHCD Launcher for Alcator C-Mod - Design, Construction, Calibration and Testing

    SciTech Connect

    J. Hosea; D. Beals; W. Beck; S. Bernabei; W. Burke; R. Childs; R. Ellis; E. Fredd; N. Greenough; M. Grimes; D. Gwinn; J. Irby; S. Jurczynski; P. Koert; C.C. Kung; G.D. Loesser; E. Marmar; R. Parker; J. Rushinski; G. Schilling; D. Terry; R. Vieira; J.R. Wilson; J. Zaks

    2005-06-27

    MIT and PPPL have joined together to fabricate a high-power lower hybrid current drive (LHCD) system for supporting steady-state AT regime research on Alcator C-Mod. The goal of the first step of this project is to provide 1.5 MW of 4.6 GHz rf [radio frequency] power to the plasma with a compact launcher which has excellent spectral selectivity and fits into a single C-Mod port. Some of the important design, construction, calibration and testing considerations for the launcher leading up to its installation on C-Mod are presented here.

  5. Progress in the RAMI analysis of a conceptual LHCD system for DEMO

    NASA Astrophysics Data System (ADS)

    Mirizzi, F.

    2014-02-01

    Reliability, Availability, Maintainability and Inspectability (RAMI) concepts and techniques, that acquired great importance during the first manned space missions, have been progressively extended to industrial, scientific and consumer equipments to assure them satisfactory performances and lifetimes. In the design of experimental facilities, like tokamaks, mainly aimed at demonstrating validity and feasibility of scientific theories, RAMI analysis has been often left aside. DEMO, the future prototype fusion reactors, will be instead designed for steadily delivering electrical energy to commercial grids, so that the RAMI aspects will assume an absolute relevance since their initial design phases. A preliminary RAMI analysis of the LHCD system for the conceptual EU DEMO reactor is given in the paper.

  6. Long reach DWDM-PON with 12.5 GHz channel spacing based on comb source seeding

    NASA Astrophysics Data System (ADS)

    Zhou, Zhao; Nie, Hai-tao; Wang, Yao-jun

    2016-07-01

    A long reach dense wavelength division multiplexing passive optical network (DWDM-PON) with 12.5 GHz channel spacing is proposed and experimentally demonstrated. An optical frequency comb source is used to provide the multiwavelength seeding light, while reflective semiconductor optical amplifiers (RSOAs) are installed in both optical line terminal (OLT) and optical network units (ONUs) as colorless transmitter. The experimental results show that the bidirectional transmission for 1.2 Gbit/s data rate is achieved over 80 km single mode fiber (SMF).

  7. Measurement of LHCD edge power deposition through modulation techniques on Alcator C-Mod

    SciTech Connect

    Faust, I. C.; Brunner, D.; LaBombard, B.; Parker, R. R.; Baek, S. G.; Chilenksi, M. A.; Hubbard, A.; Hughes, J. W.; Terry, J. L.; Shiraiwa, S.; Walk, J. R.; Wallace, G. M.; Whyte, D. G.; Edlund, E.

    2015-12-10

    The efficiency of LHCD on Alcator C-Mod drops exponentially with line average density. At reactor relevant densities (> 1 · 1020 [m{sup −3}]) no measurable current is driven. While a number of causes have been suggested, no specific mechanism has been shown to be responsible for the loss of current drive at high density. Fast modulation of the LH power was used to isolate and quantify the LHCD deposition within the plasma. Measurements from these plasmas provide unique evidence for determining a root cause. Modulation of LH power in steady plasmas exhibited no correlated change in the core temperature. A correlated, prompt response in the edge suggests that the loss in efficiency is related to a edge absorption mechanism. This follows previous results which found the generation of n{sub ||}-independent SOL currents. Multiple Langmuir probe array measurements of the conducted heat conclude that the lost power is deposited near the last closed flux surface. The heat flux induced by LH waves onto the outer divertor is calculated. Changes in the neutral pressure, ionization and hard X-ray emission at high density highlight the importance of the active divertor in the loss of efficiency. Results of this study implicate a mechanism which may occur over multiple passes, leading to power absorption near the LCFS.

  8. Measurement of LHCD edge power deposition through modulation techniques on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Faust, I. C.; Brunner, D.; LaBombard, B.; Parker, R. R.; Baek, S. G.; Chilenksi, M. A.; Edlund, E.; Hubbard, A.; Hughes, J. W.; Terry, J. L.; Shiraiwa, S.; Walk, J. R.; Wallace, G. M.; Whyte, D. G.

    2015-12-01

    The efficiency of LHCD on Alcator C-Mod drops exponentially with line average density. At reactor relevant densities (> 1 . 1020 [m-3]) no measurable current is driven. While a number of causes have been suggested, no specific mechanism has been shown to be responsible for the loss of current drive at high density. Fast modulation of the LH power was used to isolate and quantify the LHCD deposition within the plasma. Measurements from these plasmas provide unique evidence for determining a root cause. Modulation of LH power in steady plasmas exhibited no correlated change in the core temperature. A correlated, prompt response in the edge suggests that the loss in efficiency is related to a edge absorption mechanism. This follows previous results which found the generation of n||-independent SOL currents. Multiple Langmuir probe array measurements of the conducted heat conclude that the lost power is deposited near the last closed flux surface. The heat flux induced by LH waves onto the outer divertor is calculated. Changes in the neutral pressure, ionization and hard X-ray emission at high density highlight the importance of the active divertor in the loss of efficiency. Results of this study implicate a mechanism which may occur over multiple passes, leading to power absorption near the LCFS.

  9. Features of accelerated electron beam formation in LHCD experiments on FT-2 tokamak

    NASA Astrophysics Data System (ADS)

    Lashkul, S. I.; Rozhdestvensky, V. V.; Altukhov, A. B.; Dyachenko, V. V.; Esipov, L. A.; Kantor, M. Yu.; Krikunov, S. V.; Kuprienko, D. V.; Stepanov, A. Yu.

    2012-12-01

    In experiments with lower hybrid current drive (LHCD) on the FT-2 tokamak, lower hybrid (LH) waves have been successfully used for the first time to ensure effective additional heating of plasma electrons from 450 to 600 eV ( I Pl = 32 kA, Δ t RF = 14 ms, P RF = 100 kW, F = 920 MHz). Several factors influencing the efficiency of plasma heating have been discovered. In particular, significant growth of radiation losses in the LHCD regime has been found, which is probably related to an increase in the intensity of synchrotron radiation from accelerated electrons. The increase in this intensity in the 53-156 GHz frequency range was accompanied by short spikes of microwave radiation, which were observed only in a narrower frequency range (53-78 GHz) and apparently resulted from interaction of a runaway electron beam with significant local mirrors of toroidal magnetic field. A model of the additional heating of plasma electrons due to absorption of the microwave radiation generated by a beam of accelerated electrons is proposed.

  10. Calibration of electron cyclotron emission radiometer for KSTAR.

    PubMed

    Kogi, Y; Jeong, S H; Lee, K D; Akaki, K; Mase, A; Kuwahara, D; Yoshinaga, T; Nagayama, Y; Kwon, M; Kawahata, K

    2010-10-01

    We developed and installed an electron cyclotron emission radiometer for taking measurements of Korea Superconducting Tokamak Advanced Research (KSTAR) plasma. In order to precisely measure the absolute value of electron temperatures, a calibration measurement of the whole radiometer system was performed, which confirmed that the radiometer has an acceptably linear output signal for changes in input temperature. It was also found that the output power level predicted by a theoretical calculation agrees with that obtained by the calibration measurement. We also showed that the system displays acceptable noise-temperature performance around 0.23 eV.

  11. A 0.1-1.5 GHz, low jitter, area efficient PLL in 55-nm CMOS process

    NASA Astrophysics Data System (ADS)

    Bo, Zhong; Zhangming, Zhu

    2016-05-01

    A 0.1-1.5 GHz, 3.07 pS root mean squares (RMS) jitter, area efficient phase locked loop (PLL) with multiphase clock outputs is presented in this paper. The size of capacitor in the low pass filter (LPF) is significantly decreased by implementing a dual path charge pump (CP) technique in this PLL. Subject to specified power consumption, a novel optimization method is introduced to optimize the transistor size in the voltage control oscillator (VCO), CP and phase/frequency detector (PFD) in order to minimize clock jitter. This method could improve 3-6 dBc/Hz phase noise. The proposed PLL has been fabricated in 55 nm CMOS process with an integrated 16 pF metal-oxide-metal (MOM) capacitor, occupies 0.05 mm2 silicon area, the measured total power consumption is 2.8 mW @ 1.5 GHz and the phase noise is -102 dBc/Hz @ 1 MHz offset frequency. Project supported by the National Natural Science Foundation of China (Nos. 61234002, 61322405, 61306044, 61376033) and the National High-Tech Program of China (No. 2013AA014103).

  12. A 12.5 GHz-spaced optical frequency comb spanning >400 nm for near-infrared astronomical spectrograph calibration

    SciTech Connect

    Quinlan, F.; Diddams, S. A.; Ycas, G.; Osterman, S.

    2010-06-15

    A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined oscillator for near-infrared (IR) spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380-1820 nm, providing complete coverage over the H-band transmission window of earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth, and instability of the comb has been examined to estimate potential wavelength biases in spectrograph calibration. Sidemode suppression varies between 20 and 45 dB, and the optical linewidth is {approx}350 kHz at 1550 nm. The comb frequency uncertainty is bounded by {+-}30 kHz (corresponding to a radial velocity of {+-}5 cm/s), limited by the global positioning system disciplined oscillator reference. These results indicate that this comb can readily support radial velocity measurements below 1 m/s in the near IR.

  13. A Measurement of the Temperature of the Cosmic MicrowaveBackground at a Frequency of 7.5 GHz

    SciTech Connect

    Kogut, A.; Bensadoun, M.; De Amici, Giovanni; Levin, S.; Smoot,George F.; Witebsky, C.

    1989-06-01

    We have measured the intensity of the cosmic microwave background (CMB) at a frequency of 7.5 GHz (wavelength 4.0 cm) using a ground-based, total power radiometer calibrated at the horn aperture by an external cryogenic reference target. The radiometer measured the difference in antenna temperature between the reference target and the zenith sky from a dry, high-altitude site. Subtraction of foreground signals (primarily atmospheric and galactic emission) measured with the same instrument leaves the CMB as the residual. The radiometer measured the atmospheric antenna temperature by correlating the signal change with the airmass in the beam during tip scans. The small galactic signal was subtracted based on extrapolation from lower frequencies, and was checked by differential drift scans. The limiting uncertainty in the CMB measurement was the effect of ground radiation in the antenna sidelobes during atmospheric measurements. The thermodynamic temperature of the CMB at 7.5 GHz is 2.59 {+-} 0.07 K (68% confidence level).

  14. Status of PEM-based polarimetric MSE development at KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, Jinseok; Chung, Jinil; Oh, Seung Tae; Ko, Won-Ha; de Bock, Maarten; Ong, Henry; Lange, Guido

    2014-10-01

    A multi-chord PEM (photo elastic modulator)-based polarimetric motional Stark effect (MSE) system is under development for the KSTAR tokamak. The conceptual design for the front optics was optimized to preserve not only the polarization state of the input light for the MSE measurements but also the signal intensity of the existing charge exchange spectroscopy (CES) system that will share the front optics with the MSE. The optics design incorporates how to determine the number of channels and the number of fibers for each channel. A dielectric coating will be applied on the mirror to minimize the relative reflectivity and the phase shift between the two orthogonal polarization components of the incident light. Lenses with low stress-birefringence constants will be adopted to minimize non-linear and random changes in the polarization through the lenses, which is a trade-off with the rather high Faraday rotation in the lenses because the latter effect is linear and can be relatively easily calibrated out. Intensive spectrum measurements and their comparisons with the simulated spectra are done to assist the design of the bandpass filter system that will also use tilting stages to remotely control the passband. Following the system installation in 2014, the MSE measurements are expected to be performed during the 2015 KSTAR campaign.

  15. Extremely low intrinsic non-axisymmetric field in KSTAR and its implications

    NASA Astrophysics Data System (ADS)

    In, Y.; Park, J. K.; Jeon, J. M.; Kim, J.; Okabayashi, M.

    2015-04-01

    A surprisingly low level of intrinsic non-axisymmetric field (called ‘error field’) has been measured in KSTAR, suggesting at least an order of magnitude lower than in other major tokamaks. Specifically, the KSTAR was found to have an extremely low level of pitch resonant intrinsic error field at the m/n = 2/1 surface in the order of 10-5 of the magnetic field at the geometric centre, instead of 10-4 typically observed in other devices. Using a single array of in-vessel control coils (IVCCs) at the outboard midplane, the n = 1 intrinsic error field was diagnosed. Such a low level of intrinsic non-axisymmetric field as measured in KSTAR is less than or comparable to the Earth's magnetic field or a remanent field in the KSTAR plasma chamber. Considering that a very low level of n = 1 intrinsic error field (mostly associated with kink-resonance) helps the plasma to be less vulnerable to mode-locking, this might have allowed the n = 1 resonant magnetic perturbation (RMP) currents (configured to be dominantly pitch-resonant for edge localized mode (ELM) suppression) to increase without invoking a kink-resonant mode-locking, consistent with experimental observation and poloidal mode spectra calculations in KSTAR. Further clarification of the influence of the intrinsic error field in terms of a 3D structure is expected to provide a solid foundation to understand the n = 1 RMP-driven ELM suppression uniquely observed in KSTAR.

  16. Upgrade and validation on plasma of the Tore Supra CW LHCD generator

    NASA Astrophysics Data System (ADS)

    Delpech, L.; Achard, J.; Armitano, A.; Berger-By, G.; Bertrand, E.; Bouquey, F.; Chaix, J. P.; Corbel, E.; Crest, I.; Ekedahl, A.; Faisse, F.; Fejoz, P.; Garibaldi, P.; Goletto, C.; Lebourg, P.; Leroux, F.; Lombard, G.; Magne, R.; Martinez, A.; Moreau, M.; Mollard, P.; Nicolas, L.; Pagano, M.; Poli, S.; Prou, M.; Raulin, D.; Samaille, F.; Soler, B.; Thouvenin, D.; Volpe, D.; Volpe, R.

    2011-12-01

    A one year-long major upgrade of the 3.7 GHz Lower Hybrid Current Drive (LHCD) generator for the Tore Supra (TS) tokamak has been performed. It consisted in installing a first series of eight Thales Electron Devices (TED) 700 kW CW klystrons, new CW components and auxiliaries, and in modifying the transmitter control and protection software. Modifications and calibration of the sensors and the RF subsystems were completed as well. Finally, the RF power available in the generator has been increased by 35% and the pulse duration could reach 1000 s. A complete validation and optimization of the klystrons have been performed in 2010 on matched load before the generator could enter into operation. The eight klystrons connected with the Full Active Multijunction (FAM) antenna delivered 3.5 MW/50s in December 2010. The upgrade of the generator and the steps to validate the modifications are described.

  17. Wireless Channel Characterization: Modeling the 5 GHz Microwave Landing System Extension Band for Future Airport Surface Communications

    NASA Technical Reports Server (NTRS)

    Matolak, D. W.; Apaza, Rafael; Foore, Lawrence R.

    2006-01-01

    We describe a recently completed wideband wireless channel characterization project for the 5 GHz Microwave Landing System (MLS) extension band, for airport surface areas. This work included mobile measurements at large and small airports, and fixed point-to-point measurements. Mobile measurements were made via transmission from the air traffic control tower (ATCT), or from an airport field site (AFS), to a receiving ground vehicle on the airport surface. The point-to-point measurements were between ATCT and AFSs. Detailed statistical channel models were developed from all these measurements. Measured quantities include propagation path loss and power delay profiles, from which we obtain delay spreads, frequency domain correlation (coherence bandwidths), fading amplitude statistics, and channel parameter correlations. In this paper we review the project motivation, measurement coordination, and illustrate measurement results. Example channel modeling results for several propagation conditions are also provided, highlighting new findings.

  18. W-band GaN MMIC PA with 257 mW output power at 86.5 GHz

    NASA Astrophysics Data System (ADS)

    Peng, Xu; Xubo, Song; Yuanjie, Lü; Yuangang, Wang; Shaobo, Dun; Jiayun, Yin; Yulong, Fang; Guodong, Gu; Zhihong, Feng; Shujun, Cai

    2015-08-01

    A three-stage W-band GaN monolithic microwave integrated circuit power amplifier (MMIC PA) is reported. In order to manage coupling effects between all the parts of the W-band MMIC, all matching and bias networks have been first optimized using circuit simulating software and then systematically simulated on 3D full-wave electromagnetic simulator. The fabricated MMIC PA achieves a 257 mW output power at 86.5 GHz in continuous-wave mode, with an associated power added efficiency of 5.4% and an associated power gain of 6.1 dB. The power density is 459 mW/mm. Moreover, the MMIC PA offers over 100 mW in the 83-90 GHz bandwidth. Those performances were measured at drain bias of 12 V. Project supported by the National Natural Science Foundation of China (No. 61306113).

  19. Design Studies on Gyrotron for ECRH in KSTAR^*

    NASA Astrophysics Data System (ADS)

    Ahn, Saeyoung; Huh, Jin Woo; Kim, Hyoung Suk; Lee, Myoung-Jae; Song, Ho Young

    1996-11-01

    Korean National Fusion Project has started to carry out tokamak physics experiment for the Korean Superconducting Tokamak Research (KSTAR). Its current plan is scheduled to build the superconducting research reactor by the year 2002. Initial design parameters are of the major radius between 1.6 and 2.0 m and the minor radius between 0.5 and 1.0 m with plasma current between 2.0 and 5.0 MA. The toroidal field at the plasma center is about 4 tesla. Institute for Advanced Engineering (IAE) will concentrate on design studies of ECRH and gyrotron component development. Some detail plans will be presented. * Work supported by KBSI and KAERI. On leave at Ajou Univ. from NRL.

  20. Resistive wall mode active control physics design for KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Bak, J. G.; Bialek, J. M.; Berkery, J. W.; Lee, S. G.; Oh, Y. K.

    2014-01-01

    As KSTAR H-mode operation approaches the region where the resistive wall mode (RWM) can be unstable, an important issue for future long pulse, high beta plasma operation is to evaluate RWM active feedback control performance using a planned active/passive RWM stabilization system on the device. In particular, an optimal design of feedback sensors allows mode stabilization up to the highest achievable βN close to the ideal with-wall limit, βNwall, with reduced control power requirements. The computed ideal n = 1 mode structure from the DCON code has been input to the VALEN-3D code to calculate the projected performance of an active RWM control system in the KSTAR three-dimensional conducting structure device geometry. Control performance with the midplane locked mode detection sensors, off-midplane saddle loops, and magnetic pickup coils is examined. The midplane sensors measuring the radial component of the mode perturbation is found to be strongly affected by the wall eddy current. The off-axis saddle loops with proper compensation of the prompt applied field are computed to provide stabilization at βN up to 86% of βNwall but the low RWM amplitude computed in the off-axis regions near the sensors can produce a low signal-to-noise ratio. The required control power and bandwidth are also estimated with varied noise levels in the feedback sensors. Further improvements have been explored by examining a new RWM sensor design motivated by the off-midplane poloidal magnetic field sensors in NSTX. The new sensors mounted off of the copper passive stabilizer plates near the device midplane show a clear advantage in control performance corresponding to achieving 99% of βNwall without the need of compensation of the prompt field. The result shows a significant improvement of RWM feedback stabilization using the new sensor set which motivates a future feedback sensor upgrade.

  1. Conceptual communications system design in the 25.25-27.5 and 37.0-40.5 GHz frequency bands

    NASA Technical Reports Server (NTRS)

    Thompson, Michael W.

    1993-01-01

    Future space applications are likely to rely heavily on Ka-band frequencies (20-40 GHz) for communications traffic. Many space research activities are now conducted using S-band and X-band frequencies, which are becoming congested and require a degree of pre-coordination. In addition to providing relief from frequency congestion, Ka-band technologies offer potential size, weight, and power savings when compared to lower frequency bands. The use of the 37.0-37.5 and 40.0-40.5 GHz bands for future planetary missions was recently approved at the 1992 World Administrative Radio Conference (WARC-92). WARC-92 also allocated the band 25.25-27.5 GHz to the Intersatellite Service on a primary basis to accommodate Data Relay Satellite return link requirements. Intersatellite links are defined to be between artificial satellites and thus a communication link with the surface of a planetary body, such as the moon, and a relay satellite orbiting that body are not permitted in this frequency band. This report provides information about preliminary communications system concepts for forward and return links for earth-Mars and earth-lunar links using the 37.0-37.5 (return link) and 40.0-40.5 (forward link) GHz frequency bands. In this study we concentrate primarily on a conceptual system for communications between earth and a single lunar surface terminal (LST), and between earth and a single Mars surface terminal (MST). Due to large space losses, these links have the most stringent link requirements for an overall interplanetary system. The earth ground station is assumed to be the Deep Space Network (DSN) using either 34 meter or 70 meter antennas. We also develop preliminary communications concepts for a space-to-space system operating at near 26 GHz. Space-to-space applications can encompass a variety of operating conditions, and we consider several 'typical' scenarios described in more detail later in this report. Among these scenarios are vehicle-to-vehicle communications

  2. A VLA (Very Large Array) Search for 5 GHz Radio Transients and Variables at Low Galactic Latitudes

    NASA Technical Reports Server (NTRS)

    Ofek, E. O.; Frail, D. A.; Breslauer, B.; Kulkarni, S. R.; Chandra, P.; Gal-Yam, A.; Kasliwal, M. M.; Gehrels, N.

    2012-01-01

    We present the results of a 5GHz survey with the Very Large Array (VLA) and the expanded VLA, designed to search for short-lived (approx < 1 day) transients and to characterize the variability of radio sources at milli-Jansky levels. A total sky area of 2.66 sq. deg, spread over 141 fields at low Galactic latitudes (b approx equals 6 - 8 deg) was observed 16 times with a cadence that was chosen to sample timescales of days, months and years. Most of the data were reduced, analyzed and searched for transients in near real time. Interesting candidates were followed up using visible light telescopes (typical delays of 1 - 2 hr) and the X-Ray Telescope on board the Swift satellite. The final processing of the data revealed a single possible transient with a flux density of f(sub v) approx equals 2.4mJy. This implies a transients sky surface density of kappa(f(sub v) > 1.8mJy) = 0.039(exp +0.13,+0.18) (sub .0.032,.0.038) / sq. deg (1, 2 sigma confidence errors). This areal density is consistent with the sky surface density of transients from the Bower et al. survey extrapolated to 1.8mJy. Our observed transient areal density is consistent with a Neutron Stars (NSs) origin for these events. Furthermore, we use the data to measure the sources variability on days to years time scales, and we present the variability structure function of 5GHz sources. The mean structure function shows a fast increase on approximately 1 day time scale, followed by a slower increase on time scales of up to 10 days. On time scales between 10 - 60 days the structure function is roughly constant. We find that approx > 30% of the unresolved sources brighter than 1.8mJy are variable at the > 4-sigma confidence level, presumably due mainly to refractive scintillation.

  3. VizieR Online Data Catalog: Chandra Deep Field-South ATLAS 5.5GHz DR2 (Huynh+, 2015)

    NASA Astrophysics Data System (ADS)

    Huynh, M. T.; Bell, M. E.; Hopkins, A. M.; Norris, R. P.; Seymour, N.

    2016-06-01

    The eCDFS was observed with the CABB on the ATCA with the full 2048 MHz bandwidth centred at 5.5GHz. We chose a 42 pointing hexagonal mosaic with spacings of 5-arcmin (approximately 0.5FWHM of the primary beam) to uniformly sample the full 30-arcminx30-arcmin eCDFS region, centred approximately at RA=3:32:22 and DE=-27:48:37 (J2000). The 20h in 2009 and 144h in 2010 were allocated under ATCA observing programme C2028. This data resulted in a rms sensitivity of 11.9uJy and synthesized beam size of 4.9-arcsecx2.0-arcsec (Huynh et al., 2012, Cat. J/MNRAS/426/2342, H12), under hereafter Epoch 1 and Data Release 1 (DR1). Further observations were obtained in 2012 via ATCA programme C2670. The C2670 programme was conceived as a blind search for sub-mJy level sources that are variable on time-scales of months to roughly a year, with a secondary goal of testing the Variables and Slow Transients (VAST) data pipeline. A total of 54h in 2012 May-June (Epoch 2) and 47h in 2012 August (Epoch 3) was allocated to C2670, and the data was taken using the mosaicking strategy of H12. (3 data files).

  4. VizieR Online Data Catalog: The MIT-Green Bank 5GHz Survey (Bennett+, 1986-91)

    NASA Astrophysics Data System (ADS)

    Bennett, C. L.; Lawrence, C. R.; Burke, B. F.; Hewitt, J. N.; Mahoney, J.

    1999-04-01

    The MIT-Green Bank 5 GHz survey catalog was produced from four separate surveys with the National Radio Astronomy Observatory (NRAO) 91m transit telescope (Bennett et al., 1986ApJS...61....1B (MG1); Langston et al., 1990ApJS...72..621L (MG2); Griffith et al., 1990ApJS...74..129G (MG3); Griffith et al. 1991ApJS...75..801G (MG4)). The sky coverage of the various surveys is: 00h < RAB < 24h, -00d30'13" < DECB < +19d29'47" for MG1; 04h < RAJ < 21h, +17.0d < DECJ < +39d09' for MG2; 16h30m < RAB < 05h, +17d < DECB < +39d09' for MG3; and 15h30m < RAB < 02h30m, +37.00d < DECB < +50d58'48" for MG4; where RAB and DECB refer to B1950 coordinates, and RAJ and DECJ refer to J2000 coordinates. The catalog contains 20344 sources detected with a signal-to-noise ratio greater than 5 and 3836 possible detections (MG1) with a signal-to-noise ratio less than 5. Spectral indices are computed for MG1 sources also identified in the Texas 365 MHz survey (Douglas et al. 1980), and for MG1-MG4 sources also identified in the NRAO 1400 MHz Survey (Condon and Broderick 1985). (1 data file).

  5. VizieR Online Data Catalog: The MIT-Green Bank 5GHz Survey (Bennett+, 1986-91)

    NASA Astrophysics Data System (ADS)

    Bennett, C. L.; Lawrence, C. R.; Burke, B. F.; Hewitt, J. N.; Mahoney, J.

    2003-08-01

    The MIT-Green Bank 5GHz survey catalog was produced from four separate surveys with the National Radio Astronomy Observatory (NRAO) 91m transit telescope (Bennett et al., 1986ApJS...61....1B (MG1); Langston et al., 1990ApJS...72..621L (MG2); Griffith et al., 1990ApJS...74..129G (MG3); Griffith et al. 1991ApJS...75..801G (MG4)). The sky coverage of the various surveys is: 00h < RAB < 24h, -00d30'13" < DECB < +19d29'47" for MG1; 04h < RAJ < 21h, +17.0d < DECJ < +39d09' for MG2; 16h30m < RAB < 05h, +17d < DECB < +39d09' for MG3; and 15h30m < RAB < 02h30m, +37.00d < DECB < +50d58'48" for MG4; where RAB and DECB refer to B1950 coordinates, and RAJ and DECJ refer to J2000 coordinates. The catalog contains 20344 sources detected with a signal-to-noise ratio greater than 5 and 3836 possible detections (MG1) with a signal-to-noise ratio less than 5. Spectral indices are computed for MG1 sources also identified in the Texas 365MHz survey (Douglas et al. 1980), and for MG1-MG4 sources also identified in the NRAO 1400MHz Survey (Condon and Broderick 1985). (1 data file).

  6. Measurement of the dielectric properties of the epidermis and dermis at frequencies from 0.5 GHz to 110 GHz

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Wake, K.; Watanabe, S.

    2014-08-01

    Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with Gabriel’s widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20-100 GHz, the experimental results indicated larger values than those extrapolated from Gabriel’s data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency.

  7. Carbon beam extraction with 14.5 GHz electron cyclotron resonance ion source at Korea Atomic Energy Research Institute

    NASA Astrophysics Data System (ADS)

    Lee, Cheol Ho; Oh, Byung-Hoon; Chang, Dae-Sik; Jeong, Sun-Chan

    2014-02-01

    A 14.5 GHz Electron Cyclotron Resonance ion source (ECRIS) has been made to produce C4+ beam for using a carbon therapy facility and recently tested at KAERI. Highly charged carbon ions have been successfully extracted. When using only CO2 gas, the beam current of C4+ was almost 14 μA at 15 kV extraction voltage. To get higher current of the C4+ beam, while optimizing confinement magnetic field configuration (e.g., axial strengths at minimum and extraction side), gas-mixing (CO2/He), and biased disk were introduced. When the gas mixing ratio of the CO2/He gas is 1:8 at an operational pressure of 5 × 10-7 mbar and the disk was biased to -150 V relative to the ion source body, the highest current of the C4+ beam was achieved to be 50 μA, more than three times higher than previously observed only with CO2 gas. Some details on the operating conditions of the ECRIS were discussed.

  8. Carbon beam extraction with 14.5 GHz electron cyclotron resonance ion source at Korea Atomic Energy Research Institute.

    PubMed

    Lee, Cheol Ho; Oh, Byung-Hoon; Chang, Dae-Sik; Jeong, Sun-Chan

    2014-02-01

    A 14.5 GHz Electron Cyclotron Resonance ion source (ECRIS) has been made to produce C(4+) beam for using a carbon therapy facility and recently tested at KAERI. Highly charged carbon ions have been successfully extracted. When using only CO2 gas, the beam current of C(4+) was almost 14 μA at 15 kV extraction voltage. To get higher current of the C(4+) beam, while optimizing confinement magnetic field configuration (e.g., axial strengths at minimum and extraction side), gas-mixing (CO2/He), and biased disk were introduced. When the gas mixing ratio of the CO2/He gas is 1:8 at an operational pressure of 5 × 10(-7) mbar and the disk was biased to -150 V relative to the ion source body, the highest current of the C(4+) beam was achieved to be 50 μA, more than three times higher than previously observed only with CO2 gas. Some details on the operating conditions of the ECRIS were discussed. PMID:24593482

  9. 75 FR 77602 - Allocation and Designation of Spectrum for Fixed-Satellite Services in the 37.5-38.5 GHz, 40.5-41...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-13

    ... comment date for the proposed rule published November 22, 2010, 75 FR 71064, remains January 6, 2011, and... COMMISSION 47 CFR Part 25 Allocation and Designation of Spectrum for Fixed-Satellite Services in the 37.5-38... satellite systems in the 37.5-42.5 GHz band. The document contained incorrect proceeding numbers...

  10. 75 FR 71064 - Allocation and Designation of Spectrum for Fixed-Satellite Services in the 37.5-38.5 GHz, 40.5-41...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-22

    ... COMMISSION 47 CFR Part 25 Allocation and Designation of Spectrum for Fixed-Satellite Services in the 37.5-38... on technical rules for the Fixed-Satellite Service in the 37.5-42.5 GHz band. The purpose of this proceeding is to ensure that satellite operators in this band can share the band with terrestrial...

  11. 47 CFR 25.258 - Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands. 25.258 Section 25.258 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  12. 47 CFR 25.258 - Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands. 25.258 Section 25.258 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  13. 47 CFR 25.258 - Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands. 25.258 Section 25.258 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  14. 47 CFR 25.258 - Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands. 25.258 Section 25.258 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  15. 47 CFR 25.258 - Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands. 25.258 Section 25.258 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  16. Graphics processing unit-assisted density profile calculations in the KSTAR reflectometer

    NASA Astrophysics Data System (ADS)

    Seo, Seong-Heon; Oh, Dong Keun

    2014-11-01

    Wavelet transform (WT) is widely used in signal processing. The frequency modulation reflectometer in the KSTAR applies this technique to get the phase information from the mixer output measurements. Since WT is a time consuming process, it is difficult to calculate the density profile in real time. The data analysis time, however, can be significantly reduced by the use of the Graphics Processing Unit (GPU), with its powerful computing capability, in WT. A bottle neck in the KSTAR data processing exists in the data input and output (IO) process between the CPU and its peripheral devices. In this paper, the details of the WT implementation assisted by a GPU in the KSTAR reflectometer are presented and the consequent performance improvement is reported. The real time density profile calculation from the reflectometer measurements is also discussed.

  17. Graphics processing unit-assisted density profile calculations in the KSTAR reflectometer.

    PubMed

    Seo, Seong-Heon; Oh, Dong Keun

    2014-11-01

    Wavelet transform (WT) is widely used in signal processing. The frequency modulation reflectometer in the KSTAR applies this technique to get the phase information from the mixer output measurements. Since WT is a time consuming process, it is difficult to calculate the density profile in real time. The data analysis time, however, can be significantly reduced by the use of the Graphics Processing Unit (GPU), with its powerful computing capability, in WT. A bottle neck in the KSTAR data processing exists in the data input and output (IO) process between the CPU and its peripheral devices. In this paper, the details of the WT implementation assisted by a GPU in the KSTAR reflectometer are presented and the consequent performance improvement is reported. The real time density profile calculation from the reflectometer measurements is also discussed. PMID:25430234

  18. Structural safety assessment under the low temperature of KSTAR superconducting magnet-supporting post

    NASA Astrophysics Data System (ADS)

    Her, N. I.; Sa, J. W.; Cho, S.; Do, C. J.; Choi, C. H.; Kim, B. C.; Im, K. H.; Kyum, M.; Kim, W. C.; Kim, G. H.; Yoo, B. J.; Oh, Y. K.; Kim, D. L.; Kwon, M.; Lee, G. S.; Kstar Team

    2001-01-01

    A magnet-supporting post installed between the lower TF coil cooled by 4.5 K supercritical helium and the cryostat base is one of the most important components of the superconducting magnet-supporting structure for KSTAR Tokamak. This structure should be flexible to absorb thermal shrink of the magnet and should also be rigid to support the magnet weight and the plasma disruption load. The post was designed with stainless steel (SS) 316 LN and carbon fiber reinforced plastic (CFRP) that has low thermal conductivity and high structural strength at low temperature. In order to verify the fabricability and the structural safety, a whole scale prototype of the KSTAR magnet-supporting post was manufactured and tested. Both static and compressive cyclic load tests under the maximum plasma vertical disruption load and the magnet dead weight were performed. The test results showed that the magnet-supporting post of KSTAR Tokamak was fabricable and structurally rigid.

  19. Validation of plasma shape reconstruction by Cauchy condition surface method in KSTAR

    SciTech Connect

    Miyata, Y.; Suzuki, T.; Ide, S.; Hahn, S. H.; Chung, J.; Bak, J. G.; Ko, W. H.

    2014-03-15

    Cauchy Condition Surface (CCS) method is a numerical approach to reconstruct the plasma boundary and calculate the quantities related to plasma shape using the magnetic diagnostics in real time. It has been applied to the KSTAR plasma in order to establish the plasma shape reconstruction with the high elongation of plasma shape and the large effect of eddy currents flowing in the tokamak structures for the first time. For applying the CCS calculation to the KSTAR plasma, the effects by the eddy currents and the ferromagnetic materials on the plasma shape reconstruction are studied. The CCS calculation includes the effect of eddy currents and excludes the magnetic diagnostics, which is expected to be influenced largely by ferromagnetic materials. Calculations have been performed to validate the plasma shape reconstruction in 2012 KSTAR experimental campaign. Comparison between the CCS calculation and non-magnetic measurements revealed that the CCS calculation can reconstruct the accurate plasma shape even with a small I{sub P}.

  20. MHD instabilities and their control in high-beta plasmas in KSTAR

    SciTech Connect

    In, Yongkyoon

    2013-02-06

    We established 3 specific tasks as follows: Task 1 - Investigate the MHD activity during the current ramp-up phase with shaped plasmas; Task 2 - Develop a theoretical model that may show the hollowness dependent instability; Task 3 - Explore the beta-limiting instabilities. To address each task, FAR-TECH actively participated in the 2012 KSTAR run-campaign, which helped us make productive progress. Specifically, the shaping dependence of MHD activity during current ramp-up phase was investigated using dedicated run-time in KSTAR (October 4 and 9, 2012), which was also attempted to address the hollowness of temperature (or pressure) profiles. Also, a performance-limiting disruption, which occurred in a relatively high intermediate beta plasma (shot 7110) in KSTAR ({beta}{sub N} ~ 1.7), was studied, and the preliminary analysis shows that the disruption might not be stability-limited but likely density-limited.

  1. Mechanical and Thermal Characteristics of Insulation Materials for the KSTAR Magnet System at Cryogenic Temperature

    NASA Astrophysics Data System (ADS)

    Chung, Wooho; Lim, Bungsu; Kim, Myungkyu; Park, Hyunki; Kim, Keeman; Chu, Yong; Lee, Sangil

    2004-06-01

    The KSTAR(Korea Superconducting Tokamak Advanced Research) superconducting magnet is electrically insulated by the composite material of epoxy resin and glass fiber (2.5 kV/mm) and Kapton (8 kV/mm). The insulation composite material of epoxy resin and glass fiber is prepared using a VPI (Vacuum Pressure Impregnation) process. The superconducting magnet is under mechanical stress caused by the large temperature difference between the operation temperature of the magnet and room temperature. The large electro-magnetic force during the operation of the magnet is also exerted on the magnet. Therefore, the characteristics of the insulation material at cryogenic temperatures are very important and the tensile stress and thermal expansion coefficient for the insulation materials of the KSTAR superconducting magnet are measured. This paper presents results on mechanical properties of the insulation material for KSTAR magnets, such as density, ultimate tensile stress and thermal contraction between room temperature and cryogenic temperatures.

  2. Resistive wall mode active control physics design for KSTAR

    SciTech Connect

    Park, Y. S. Sabbagh, S. A.; Bialek, J. M.; Berkery, J. W.; Bak, J. G.; Lee, S. G.; Oh, Y. K.

    2014-01-15

    As KSTAR H-mode operation approaches the region where the resistive wall mode (RWM) can be unstable, an important issue for future long pulse, high beta plasma operation is to evaluate RWM active feedback control performance using a planned active/passive RWM stabilization system on the device. In particular, an optimal design of feedback sensors allows mode stabilization up to the highest achievable β{sub N} close to the ideal with-wall limit, β{sub N}{sup wall}, with reduced control power requirements. The computed ideal n = 1 mode structure from the DCON code has been input to the VALEN-3D code to calculate the projected performance of an active RWM control system in the KSTAR three-dimensional conducting structure device geometry. Control performance with the midplane locked mode detection sensors, off-midplane saddle loops, and magnetic pickup coils is examined. The midplane sensors measuring the radial component of the mode perturbation is found to be strongly affected by the wall eddy current. The off-axis saddle loops with proper compensation of the prompt applied field are computed to provide stabilization at β{sub N} up to 86% of β{sub N}{sup wall} but the low RWM amplitude computed in the off-axis regions near the sensors can produce a low signal-to-noise ratio. The required control power and bandwidth are also estimated with varied noise levels in the feedback sensors. Further improvements have been explored by examining a new RWM sensor design motivated by the off-midplane poloidal magnetic field sensors in NSTX. The new sensors mounted off of the copper passive stabilizer plates near the device midplane show a clear advantage in control performance corresponding to achieving 99% of β{sub N}{sup wall} without the need of compensation of the prompt field. The result shows a significant improvement of RWM feedback stabilization using the new sensor set which motivates a future feedback sensor upgrade.

  3. VizieR Online Data Catalog: MGIV (Fourth MIT-Green Bank) 5GHz Survey (Griffith+ 1991)

    NASA Astrophysics Data System (ADS)

    Griffith, M.; Langston, G.; Heflin, M.; Conner, S.; Burke, B.

    1998-10-01

    The MIT-Green Bank IV (MG IV) 5 GHz survey covers 0.504 sr of sky in the right ascension range 15.5 to 2.5 hours, between +37.00 and +50.98 degrees declination (B1950). The final MG IV catalog contains 3427 sources detected with a signal-to-noise ratio greater than 5. The catalog was produced from two separate north and south surveys with the National Radio Astronomy Observatory (NRAO) 91m transit telescope. The north survey was produced from data collected while scanning the telescope north from +39.0 to +50.98 degrees declination and the south survey from data collected from scans from +48.98 to +37.00 degrees declination. The completeness and reliability of the final source list is checked by examination of north and south source lists in a twice observed comparison region, lying between +39.15 and +48.83 degrees declination and excluding the area between +/-10 degrees Galactic latitude. The comparison region covers 0.270 sr of sky and contains 1094 sources. In this region, the MG IV catalog contains 423 sources brighter than 90 mJy and is shown to be 99.1 +/- 1.2% complete at this flux density level. Spectral indices are computed for sources identified in the NRAO 1400 MHz Survey (published by Condon and Broderick in 1985). A comparison of the spectral index distributions between +/- 10 and outside of +/- 10 degrees Galactic latitude is presented. (1 data file).

  4. A sample of small-sized compact steep-spectrum radio sources: VLBI images and VLA polarization at 5 GHz

    NASA Astrophysics Data System (ADS)

    Dallacasa, D.; Orienti, M.; Fanti, C.; Fanti, R.; Stanghellini, C.

    2013-07-01

    Global Very Long Baseline Interferometry (VLBI) observations at 5 GHz have been performed to study the source morphology in 10 compact steep-spectrum (CSS) sources selected from the Peacock & Wall catalogue with the aim of finding asymmetric structures produced by the interaction with the ambient medium. The combination of these data and earlier 1.7-GHz observations allows the study of the spectral index distribution across the source structure and the unambiguous determination of the nature of each component. In seven sources we detected the core component with a flat or inverted spectrum. In six sources the radio emission has a two-sided morphology and comes mainly from steep-spectrum extended structures, like lobes, jets and hotspots. Only one source, 0319+121, has a one-sided core-jet structure. In three out of the six sources with a two-sided structure the flux density arising from the lobes is asymmetric, and the brightest lobe is the one closest to the core, suggesting that the jets are expanding in an inhomogeneous ambient medium which may influence the source growth. The interaction between the jet and the environment may slow down the source expansion and enhance the luminosity due to severe radiative losses, likely producing an excess of CSS radio sources in flux density limited samples. The lobes of the other three asymmetric sources have a brighter-when-farther behaviour, in agreement with what is expected by projection and relativistic effects. Simultaneous Very Large Array observations carried out to investigate the polarization properties of the targets detected significant polarized emission (˜5.5 per cent) only from the quasar 0319+121.

  5. Advances in multi-megawatt lower hybrid technology in support of steady-state tokamak operation

    NASA Astrophysics Data System (ADS)

    Delpech, L.; Achard, J.; Armitano, A.; Artaud, J. F.; Bae, Y. S.; Belo, J. H.; Berger-By, G.; Bouquey, F.; Cho, M. H.; Corbel, E.; Decker, J.; Do, H.; Dumont, R.; Ekedahl, A.; Garibaldi, P.; Goniche, M.; Guilhem, D.; Hillairet, J.; Hoang, G. T.; Kim, H. S.; Kim, J. H.; Kim, H.; Kwak, J. G.; Magne, R.; Mollard, P.; Na, Y. S.; Namkung, W.; Oh, Y. K.; Park, S.; Park, H.; Peysson, Y.; Poli, S.; Prou, M.; Samaille, F.; Yang, H. L.; The Tore Supra Team

    2014-10-01

    It has been demonstrated that lower hybrid current drive (LHCD) systems play a crucial role for steady-state tokamak operation, owing to their high current drive (CD) efficiency and hence their capability to reduce flux consumption. This paper describes the extensive technology programmes developed for the Tore Supra (France) and the KSTAR (Korea) tokamaks in order to bring continuous wave (CW) LHCD systems into operation. The Tore Supra LHCD generator at 3.7 GHz is fully CW compatible, with RF power PRF = 9.2 MW available at the generator to feed two actively water-cooled launchers. On Tore Supra, the most recent and novel passive active multijunction (PAM) launcher has sustained 2.7 MW (corresponding to its design value of 25 MW m-2 at the launcher mouth) for a 78 s flat-top discharge, with low reflected power even at large plasma-launcher gaps. The fully active multijunction (FAM) launcher has reached 3.8 MW of coupled power (24 MW m-2 at the launcher mouth) with the new TH2103C klystrons. By combining both the PAM and FAM launchers, 950 MJ of energy, using 5.2 MW of LHCD and 1 MW of ICRH (ion cyclotron resonance heating), was injected for 160 s in 2011. The 3.7 GHz CW LHCD system will be a key element within the W (for tungsten) environment in steady-state Tokamak (WEST) project, where the aim is to test ITER technologies for high heat flux components in relevant heat flux density and particle fluence conditions. On KSTAR, a 2 MW LHCD system operating at 5 GHz is under development. Recently the 5 GHz prototype klystron has reached 500 kW/600 s on a matched load, and studies are ongoing to design a PAM launcher. In addition to the studies of technology, a combination of ray-tracing and Fokker-Planck calculations have been performed to evaluate the driven current and the power deposition due to LH waves, and to optimize the N∥ spectrum for the future launcher design. Furthermore, an LHCD system at 5 GHz is being considered for a future upgrade of the ITER

  6. Progress in development of neutron energy spectrometer for deuterium plasma operation in KSTAR

    SciTech Connect

    Tomita, H. Yamashita, F.; Nakayama, Y.; Morishima, K.; Yamamoto, Y.; Sakai, Y.; Hayashi, S.; Kawarabayashi, J.; Iguchi, T.; Cheon, M. S.; Isobe, M.; Ogawa, K.

    2014-11-15

    Two types of DD neutron energy spectrometer (NES) are under development for deuterium plasma operation in KSTAR to understand behavior of beam ions in the plasma. One is based on the state-of-the-art nuclear emulsion technique. The other is based on a coincidence detection of a recoiled proton and a scattered neutron caused by an elastic scattering of an incident DD neutron, which is called an associated particle coincidence counting-NES. The prototype NES systems were installed at J-port in KSTAR in 2012. During the 2012 and 2013 experimental campaigns, multiple shots-integrated neutron spectra were preliminarily obtained by the nuclear emulsion-based NES system.

  7. Development of a particle injection system for impurity transport study in KSTAR

    SciTech Connect

    Lee, H. Y.; Hong, Joohwan; Lee, Seung Hun; Jang, Siwon; Jang, Juhyeok; Jeon, Taemin; Park, Jae Sun; Choe, Wonho; Hong, Suk-Ho

    2014-11-15

    A solid particle injection system is developed for KSTAR. The system has a compact size, compatibility with a strong magnetic field and high vacuum environment, and the capability to inject a small amount of solid particles with a narrow injection angle. The target flight-distance of 10 cm has been achieved with a particle loss rate of less than 10%. Solid impurity particles such as tungsten and carbon will be injected by this system at the midplane in KSTAR. The impurity transport feature will be studied with a soft X-ray array, a vacuum ultra-violet diagnostic, and Stand Alone Non-Corona code.

  8. Development of a KSTAR ICRF antenna for long pulse operation

    NASA Astrophysics Data System (ADS)

    Bae, Y. D.; Kwak, J. G.; Kim, S. K.; Yoon, J. S.; Hong, B. G.; Hwang, C. K.; Wang, S. J.; Jeong, S. U.

    2003-09-01

    A prototype ion cyclotron range of frequency (ICRF) antenna with RF power of 6 MW has been developed for the long pulse (300 s), high power operation in the Korea superconducting tokamak advanced research (KSTAR) tokamak. Cooling paths in the antenna were carefully designed to remove the dissipated RF power loss. An RF power test has been performed to estimate the standoff capability of the antenna. A high power RF test at a frequency of 30 MHz gives a standoff voltage of 30.5 kVp for 60 s and 23.2 kVp for 300 s (without cooling). During the RF pulse, the peak voltage, forward/reflected powers, temperature of the antenna, and gas pressure are measured. A vacuum feedthrough of 1 MW RF power has been developed, which has two alumina ceramic cylinders and an O-ring seal. For cooling of the ceramic parts, dry air is injected into the ceramic surface through two outer nozzles. Independent cooling water channels are installed to cool the inner conductor of the feedthrough. RF high voltage tests show that stable operation is possible, with a peak voltage of 28.9 kVp for 300 s, without any severe damage.

  9. Operation results of the KSTAR far infrared interferometer

    NASA Astrophysics Data System (ADS)

    Juhn, June-Woo; Lee, K. C.; Wi, H. M.; Kim, Y. S.; Nam, Y. U.

    2016-11-01

    The 2015 KSTAR experimental campaign was the first year of routine measurement with a far infrared interferometer (FIRI) utilizing 118.87 μm CH3OH lasers at maximum 200 mW CW beam power. By using rtEFIT reconstruction, the path lengths of interferometers can be calculated and so the line-averaged electron densities n ¯ e from the FIRI and a millimeter-wave interferometer were in excellent agreement. In this way, the number of successfully diagnosed discharges is counted: 1003 shots or 83.7% of sustained discharges, defined as shots of plasma current IP ≥ 0.3 MA with pulse lengths tf ≥ 2.0 s, have good-quality FIRI data within a few fringe jump errors. In addition, real-time H-mode density feedback control based on the FIRI was also successfully achieved with supersonic molecular beam injection as an actuator. Both constant density and controlled linear increment with a ramp-up rate of 1.0 × 1019 m-3 s-1 were achieved.

  10. Predictive modeling of pedestal structure in KSTAR using EPED model

    SciTech Connect

    Han, Hyunsun; Kim, J. Y.; Kwon, Ohjin

    2013-10-15

    A predictive calculation is given for the structure of edge pedestal in the H-mode plasma of the KSTAR (Korea Superconducting Tokamak Advanced Research) device using the EPED model. Particularly, the dependence of pedestal width and height on various plasma parameters is studied in detail. The two codes, ELITE and HELENA, are utilized for the stability analysis of the peeling-ballooning and kinetic ballooning modes, respectively. Summarizing the main results, the pedestal slope and height have a strong dependence on plasma current, rapidly increasing with it, while the pedestal width is almost independent of it. The plasma density or collisionality gives initially a mild stabilization, increasing the pedestal slope and height, but above some threshold value its effect turns to a destabilization, reducing the pedestal width and height. Among several plasma shape parameters, the triangularity gives the most dominant effect, rapidly increasing the pedestal width and height, while the effect of elongation and squareness appears to be relatively weak. Implication of these edge results, particularly in relation to the global plasma performance, is discussed.

  11. Recent experimental results and future plan in KSTAR

    NASA Astrophysics Data System (ADS)

    Kwak, Jong-Gu; Lee, Sang-Gon; Bae, Young-Sun; Park, Boung-Ho; Kim, Jin-Young; KSTAR Team

    2014-10-01

    In this talk, the recent results of KSTAR will be presented focusing on extention of operational boundary in long-pulse discharges and highlights in experimental physics. H-mode discharges has been sustained longer and the operational regime of plasma parameters has been significantly extended in terms of heating power and plasma current. The long-pulse operation is in accordance with ITER requirement, i.e., in ITER similar shape, low safety factor (q95 ~ 3) and normalized beta (~2.0) with real-time control of density and power. Both ELM suppression and mitigation are discovered in wide range of RMP coil configuration and the suppression window in the edge safety factor has extended from 6.5 to 3.9 indicating the strong impact of resonant component. Beside RMP ELM suppression, it is also investigated the effect of other techniques on ELMs, such as edge heating by ECH and cooling by SMBI. Detailed evaluation of error field (EF) has been performed by 4 segment compass scan by the internal coils and the measured level of intrinsic error field is an order of magnitude lower than other tokamaks. In addition to the above topics, it is summarized the recent results on rotation & transport physics, newly installed diagnostics, MHD and fast ion activities, followed by the near future plan.

  12. Commissioning of 170 GHz, 1 MW EC H&CD in KSTAR

    NASA Astrophysics Data System (ADS)

    Jeong, J. H.; Sakamoto, K.; Joung, M.; Park, S. I.; Kim, H. J.; Han, W. S.; Kim, J. S.; Bae, Y. S.; Yang, H. L.; Kwak, J. G.; Kwon, M.; Namkung, W.; Park, H.; Cho, M. H.; Kajiwara, K.; Oda, Y.; Hosea, J.; Ellis, R.; Doane, J.; Olstad, R.

    2012-09-01

    The newly installed electron cyclotron heating and current drive (EC H&CD) system with a frequency of 170 GHz was successfully commissioned and used for the second-harmonic ECH-assisted startup in 2011 operational campaign of the KSTAR. As a RF power source, ITER pre-prototype of 170 GHz, 1 MW continuous-wave gyrotron, is loaned from the Japan Atomic Energy Agency (JAEA). During the KSTAR 2011 plamma campaign, maxumum pulse length of 10 sec at 0.6 MW EC beam was reliably injected into the plasma and the 170 GHz second harmonic ECH-assisted start-up was successful leading to reduce the flux consumption at toroidal magnetic field of 3 T. As a result, the flux consumption until the plasma current flat-top was reduced from 4.13 Wb for pure Ohmic to 3.62 Wb (12 % reduction) for the perpendicular injection. When the EC beam is launched with toroidal angle of 20 deg in co-CD direction, more reduced magnetic flux consumption was obtained with 3.14 Wb (24 % reduction) compared with pure OH plasmas. In recent, the gyrotron has been successfully commissioned with the output power of 1 MW and the pulse duration of 20 sec in KSTAR. This paper presents successful commissioning of 170 GHz EC H&CD system in KSTAR as well as the heating and startup experimental results.

  13. Steady-state ELM-suppressed H-modes from KSTAR to ITER and beyond

    NASA Astrophysics Data System (ADS)

    in, Yongkyoon; Kwak, J. G.; KSTAR Team

    2014-10-01

    Long-pulse, steady-state high-performance plasma is not only an important mission in KSTAR, but also directly relevant to ITER. While demonstrating the pulse-length of more than 20 sec H-mode flat-top in 2013, KSTAR has been exploring various means to achieve and sustain steady-state, ELM-suppressed/mitigated H-modes using versatile in-vessel control coils (IVCC), ECCD/ECH, and/or SMBI. In particular, taking advantage of the versatile 3-rows of IVCC, KSTAR accomplished both n = 1 and n = 2 RMP-driven, ELM-suppressed regimes that lasted up to 4 sec so far (limited by the discharge pulse length, not by any physics constraints, and will be extended up to 10 sec in 2014.) We also found the use of n = 2 RMP has prevented a locked-mode from being disruptive (at least within the RMP phase). To cope with run-away electrons and/or off-normal events, a soft landing algorithm has been developed and confirmed capable of ramping down the plasma current safely. The enhanced understanding and demonstration of steady-state, high-performance plasmas in KSTAR will elevate the level of confidence about the success of ITER and beyond. Supported by Ministry of Science, ICT, and Future Planning in Korea.

  14. Real time MHD mode control using ECCD in KSTAR: Plan and requirements

    SciTech Connect

    Joung, M.; Woo, M. H.; Jeong, J. H.; Hahn, S. H.; Yun, S. W.; Lee, W. R.; Bae, Y. S.; Oh, Y. K.; Kwak, J. G.; Yang, H. L.; Namkung, W.; Park, H.; Cho, M. H.; Kim, M. H.; Kim, K. J.; Na, Y. S.; Hosea, J.; Ellis, R.

    2014-02-12

    For a high-performance, advanced tokamak mode in KSTAR, we have been developing a real-time control system of MHD modes such as sawtooth and Neo-classical Tearing Mode (NTM) by ECH/ECCD. The active feedback control loop will be also added to the mirror position and the real-time detection of the mode position. In this year, for the stabilization of NTM that is crucial to plasma performance we have implemented open-loop ECH antenna control system in KSTAR Plasma Control System (PCS) for ECH mirror movement during a single plasma discharge. KSTAR 170 GHz ECH launcher which was designed and fabricated by collaboration with PPPL and POSTECH has a final mirror of a poloidally and toroidally steerable mirror. The poloidal steering motion is only controlled in the real-time NTM control system and its maximum steering speed is 10 degree/sec by DC motor. However, the latency of the mirror control system and the return period of ECH antenna mirror angle are not fast because the existing launcher mirror control system is based on PLC which is connected to the KSTAR machine network through serial to LAN converter. In this paper, we present the design of real time NTM control system, ECH requirements, and the upgrade plan.

  15. Status of KSTAR 170 GHz, 1 MW Electron Cyclotron Heating and Current Drive System

    SciTech Connect

    Joung, M.; Bae, Y. S.; Jeong, J. H.; Park, S.; Kim, H. J.; Yang, H. L.; Park, H.; Cho, M. H.; Namkung, W.; Hosea, J.; Ellis, R.; Sakamoto, K.; Kajiwara, K.; Doane, J.

    2011-12-23

    A 170 GHz Electron Cyclotron Heating and Current Drive (ECH/CD) system on KSTAR is designed to launch total 2.4 MW of power for up to 300 sec into the plasma. At present the first 1 MW ECH/CD system is under installation and commissioning for 2011 KSTAR campaign. The 170 GHz, 1 MW, 300 sec gyrotron and the matching optics unit (MOU) will be provided from JAEA under collaboration between NFRI and JAEA. The transmission line consists of MOU and 70 m long 63.5 mm ID corrugated waveguides with the eight miter bends. The 1 MW, 10 sec launcher is developed based on the existing two-mirror front-end launcher in collaboration with Princeton Plasma Physics Laboratory and Pohang University of Science and Technology, and is installed on the low field side in the KSTAR equatorial plane. The mirror pivot is located at 30 cm below from the equatorial plane. 3.6 MVA power supply system is manufactured and now is under commissioning to meet the triode gun operation of JAEA gyrotron. The power supply consists of 66 kV/55 A cathode power supply, mode-anode system, and 50 kV/160 mA body power supply. In this paper, the current status of KSTAR 170 GHz, 1 MW ECH/CD system will be presented as well as the experimental plan utilizing 170 GHz new ECH/CD system.

  16. Real time MHD mode control using ECCD in KSTAR: Plan and requirements

    NASA Astrophysics Data System (ADS)

    Joung, M.; Woo, M. H.; Jeong, J. H.; Hahn, S. H.; Yun, S. W.; Lee, W. R.; Bae, Y. S.; Oh, Y. K.; Kwak, J. G.; Yang, H. L.; Namkung, W.; Park, H.; Cho, M. H.; Kim, M. H.; Kim, K. J.; Na, Y. S.; Hosea, J.; Ellis, R.

    2014-02-01

    For a high-performance, advanced tokamak mode in KSTAR, we have been developing a real-time control system of MHD modes such as sawtooth and Neo-classical Tearing Mode (NTM) by ECH/ECCD. The active feedback control loop will be also added to the mirror position and the real-time detection of the mode position. In this year, for the stabilization of NTM that is crucial to plasma performance we have implemented open-loop ECH antenna control system in KSTAR Plasma Control System (PCS) for ECH mirror movement during a single plasma discharge. KSTAR 170 GHz ECH launcher which was designed and fabricated by collaboration with PPPL and POSTECH has a final mirror of a poloidally and toroidally steerable mirror. The poloidal steering motion is only controlled in the real-time NTM control system and its maximum steering speed is 10 degree/sec by DC motor. However, the latency of the mirror control system and the return period of ECH antenna mirror angle are not fast because the existing launcher mirror control system is based on PLC which is connected to the KSTAR machine network through serial to LAN converter. In this paper, we present the design of real time NTM control system, ECH requirements, and the upgrade plan.

  17. Performance of a New Ion Source for KSTAR Tokamak Plasma Heating

    NASA Astrophysics Data System (ADS)

    Tae-Seong, Kim; Seung, Ho Jeong; Doo, Hee Chang; Kwang, Won Lee; Sang-Ryul, In

    2014-06-01

    In the experimental campaign of 2010 and 2011 on KSTAR, the NBI-1 system was equipped with one prototype ion source and operated successfully, providing a neutral beam power of 0.7-1.6 MW to the tokamak plasma. The new ion source planned for the 2012 KSTAR campaign had a much more advanced performance compared with the previous one. The target performance of the new ion source was to provide a neutral deuterium beam of 2 MW to the tokamak plasma. The ion source was newly designed, fabricated, and assembled in 2011. The new ion source was then conditioned up to 64 A/100 keV over a 2-hour beam extraction and performance tested at the NB test stand (NBTS) at the Korea Atomic Energy Research Institute (KAERI) in 2012. The measured optimum perveance at which the beam divergence is a minimum was about 2.5 μP, and the minimum beam divergent angle was under 1.0° at 60 keV. These results indicate that the 2.0 MW neutral beam power at 100 keV required for the heating of plasma in KSTAR can be delivered by the installation of the new ion source in the KSTAR NBI-1 system.

  18. Radiometric measurements over bare and vegetated fields at 1.4 GHz and 5 GHz frequencies. [Beltsville Agricultural Research Center, Maryland

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Mcmurtrey, J. E., III; Engman, E. T.; Jackson, T. J.; Schmugge, T. J.; Gould, W. I.; Glazar, W. S.; Fuchs, J. E. (Principal Investigator)

    1981-01-01

    Microwave emission from bare and vegetated fields was measured with dual polarized radiometers at 1.4 GHz and 5 GHz frequencies. The measured brightness temperatures over bare fields are shown to compare favorably with those calculated from radiative transfer theory with two constant parameters characterizing surface roughness effect. The presence of vegetation cover is found to reduce the sensitivity to soil moisture variation. This sensitivity reduction is generally pronounced the denser, the vegetation cover and the higher the frequency of observation. The effect of vegetation cover is also examined with respect to the measured polarization factor at both frequencies. With the exception of dry corn fields, the measured polarization factor over vegetated fields is found appreciably reduced compared to that over bare fields. A much larger reduction in this factor is found at 5GHz than at 1.4GHz frequency.

  19. Characteristics of the First H-mode Discharges in KSTAR

    SciTech Connect

    Yoon, S. W.; Ahn, J.W.; Jeon, Y. M.; Suzuki, T.; Hahn, S. H.; Ko, W. H.; Lee, K. D.; Chung, J. I.; Nam, Y. U.; Kim, H. S.; Kim, W. C.; Oh, Y. K.; Kwak, J. G.; Park, Y. S.; Sabbagh, S. A.; Humphreys, D. A.; Na, Y. S.; Kim, K. M.; Yun, G. S.; Hyatt, A. W.; Gohil, P.; Bae, Y. S.; Yang, H. L.; Park, H.; Kwon, M.; Lee, G. S.

    2011-01-01

    Typical ELMy H-mode discharges have been obtained in the KSTAR tokamak with the combined auxiliary heating of neutral beam injection (NBI) and electron cyclotron resonant heating (ECRH). The minimum external heating power required for the L-H transition is about 0.9MW for a line-averaged density of similar to 2.0 x 10(19) m(-3). There is a clear indication of the increase in the L-H threshold power with decreasing density for densities lower than similar to 2 x 10(19) m(-3). The L-H transitions typically occurred shortly after the beginning of plasma current flattop (I(p) = 0.6 MA) period and after the fast shaping to a highly elongated double-null divertor configuration. The maximum heating power available was marginal for the L-H transition, which is also implied by the relatively slow transition time (>10 ms) and the synchronization of the transition with large sawtooth crashes. The initial analysis of thermal energy confinement time (tau(E)) indicates that tau(E) is higher than the prediction of multi-machine scaling laws by 10-20%. A clear increase in electron and ion temperature in the pedestal is observed in the H-mode phase but the core temperature does not change significantly. On the other hand, the toroidal rotation velocity increased over the whole radial range in the H-mode phase. The measured ELM frequency was around 10-30 Hz for the large ELM bursts and 50-100 Hz for the smaller ones. In addition, very small and high frequency (200-300 Hz) ELMs appeared between large ELM spikes when the ECRH is added to the NBI-heated H-mode plasmas. The drop of total stored energy during a large ELM is up to 5% in most cases.

  20. Characteristics of the first H-mode discharges in KSTAR

    NASA Astrophysics Data System (ADS)

    Yoon, S. W.; Ahn, J.-W.; Jeon, Y. M.; Suzuki, T.; Hahn, S. H.; Ko, W. H.; Lee, K. D.; Chung, J. I.; Nam, Y. U.; Kim, J.; Hong, S. H.; Kim, H.-S.; Kim, W. C.; Oh, Y. K.; Kwak, J. G.; Park, Y. S.; Sabbagh, S. A.; Humpreys, D.; Na, Y.-S.; Kim, K. M.; Yun, G. S.; Hyatt, A.; Gohil, P.; Bae, Y. S.; Yang, H. L.; Park, H. K.; Kwon, M.; Lee, G. S.; KSTAR Team

    2011-11-01

    Typical ELMy H-mode discharges have been obtained in the KSTAR tokamak with the combined auxiliary heating of neutral beam injection (NBI) and electron cyclotron resonant heating (ECRH). The minimum external heating power required for the L-H transition is about 0.9 MW for a line-averaged density of ~2.0 × 1019 m-3. There is a clear indication of the increase in the L-H threshold power with decreasing density for densities lower than ~2 × 1019 m-3. The L-H transitions typically occurred shortly after the beginning of plasma current flattop (Ip = 0.6 MA) period and after the fast shaping to a highly elongated double-null divertor configuration. The maximum heating power available was marginal for the L-H transition, which is also implied by the relatively slow transition time (>10 ms) and the synchronization of the transition with large sawtooth crashes. The initial analysis of thermal energy confinement time (τE) indicates that τE is higher than the prediction of multi-machine scaling laws by 10-20%. A clear increase in electron and ion temperature in the pedestal is observed in the H-mode phase but the core temperature does not change significantly. On the other hand, the toroidal rotation velocity increased over the whole radial range in the H-mode phase. The measured ELM frequency was around 10-30 Hz for the large ELM bursts and 50-100 Hz for the smaller ones. In addition, very small and high frequency (200-300 Hz) ELMs appeared between large ELM spikes when the ECRH is added to the NBI-heated H-mode plasmas. The drop of total stored energy during a large ELM is up to 5% in most cases.

  1. Quasi 3D ECE imaging system for study of MHD instabilities in KSTAR

    SciTech Connect

    Yun, G. S. Choi, M. J.; Lee, J.; Kim, M.; Leem, J.; Nam, Y.; Choe, G. H.; Lee, W.; Park, H. K.; Park, H.; Woo, D. S.; Kim, K. W.; Domier, C. W.; Luhmann, N. C.; Ito, N.; Mase, A.; Lee, S. G.

    2014-11-15

    A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B{sub 0} = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.

  2. Versatile controllability of non-axisymmetric magnetic perturbations in KSTAR experiments

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; Jeon, Y. M.; in, Y.; Kim, J.; Yoon, S. W.; Hahn, S. H.; Ahn, H. S.; Woo, M. H.; Park, B. H.; Bak, J. G.; Kstar Team

    2015-11-01

    A newly upgraded IVCC (In-Vessel Control Coil) system equipped with four broadband power supplies, along with current connection patch panel, will be presented and discussed in terms of its capability on various KSTAR experiments. Until the last run-campaign, there were impressive experimental results on ELM(Edge Localized Mode) control experiments using the 3D magnetic field, but the non-axisymmetric field configuration could not be changed in a shot, let alone the limited number of accessible configurations. Introducing the new power supplies, such restrictions have been greatly reduced. Based on the preliminary commissioning results for 2015 KSTAR run-campaign, this new system has been confirmed to easily cope with various dynamic demands for toroidal and poloidal phases of 3D magnetic field in a shot. This enables us to diagnose the plasma response in more detail and to address the 3-D field impacts on the ELM behaviors better than ever.

  3. Improvement of a plasma uniformity of the 2nd ion source of KSTAR neutral beam injector

    NASA Astrophysics Data System (ADS)

    Jeong, S. H.; Kim, T. S.; Lee, K. W.; Chang, D. H.; In, S. R.; Bae, Y. S.

    2014-02-01

    The 2nd ion source of KSTAR (Korea Superconducting Tokamak Advanced Research) NBI (Neutral Beam Injector) had been developed and operated since last year. A calorimetric analysis revealed that the heat load of the back plate of the ion source is relatively higher than that of the 1st ion source of KSTAR NBI. The spatial plasma uniformity of the ion source is not good. Therefore, we intended to identify factors affecting the uniformity of a plasma density and improve it. We estimated the effects of a direction of filament current and a magnetic field configuration of the plasma generator on the plasma uniformity. We also verified that the operation conditions of an ion source could change a uniformity of the plasma density of an ion source.

  4. Improvement of a plasma uniformity of the 2nd ion source of KSTAR neutral beam injector

    SciTech Connect

    Jeong, S. H. Kim, T. S.; Lee, K. W.; Chang, D. H.; In, S. R.; Bae, Y. S.

    2014-02-15

    The 2nd ion source of KSTAR (Korea Superconducting Tokamak Advanced Research) NBI (Neutral Beam Injector) had been developed and operated since last year. A calorimetric analysis revealed that the heat load of the back plate of the ion source is relatively higher than that of the 1st ion source of KSTAR NBI. The spatial plasma uniformity of the ion source is not good. Therefore, we intended to identify factors affecting the uniformity of a plasma density and improve it. We estimated the effects of a direction of filament current and a magnetic field configuration of the plasma generator on the plasma uniformity. We also verified that the operation conditions of an ion source could change a uniformity of the plasma density of an ion source.

  5. Analysis of edge density fluctuation measured by trial KSTAR beam emission spectroscopy system

    SciTech Connect

    Nam, Y. U.; Zoletnik, S.; Lampert, M.; Kovacsik, A.

    2012-10-15

    A beam emission spectroscopy (BES) system based on direct imaging avalanche photodiode (APD) camera has been designed for Korea Superconducting Tokamak Advanced Research (KSTAR) and a trial system has been constructed and installed for evaluating feasibility of the design. The system contains two cameras, one is an APD camera for BES measurement and another is a fast visible camera for position calibration. Two pneumatically actuated mirrors were positioned at front and rear of lens optics. The front mirror can switch the measurement between edge and core region of plasma and the rear mirror can switch between the APD and the visible camera. All systems worked properly and the measured photon flux was reasonable as expected from the simulation. While the measurement data from the trial system were limited, it revealed some interesting characteristics of KSTAR plasma suggesting future research works with fully installed BES system. The analysis result and the development plan will be presented in this paper.

  6. Improvement of a plasma uniformity of the 2nd ion source of KSTAR neutral beam injector.

    PubMed

    Jeong, S H; Kim, T S; Lee, K W; Chang, D H; In, S R; Bae, Y S

    2014-02-01

    The 2nd ion source of KSTAR (Korea Superconducting Tokamak Advanced Research) NBI (Neutral Beam Injector) had been developed and operated since last year. A calorimetric analysis revealed that the heat load of the back plate of the ion source is relatively higher than that of the 1st ion source of KSTAR NBI. The spatial plasma uniformity of the ion source is not good. Therefore, we intended to identify factors affecting the uniformity of a plasma density and improve it. We estimated the effects of a direction of filament current and a magnetic field configuration of the plasma generator on the plasma uniformity. We also verified that the operation conditions of an ion source could change a uniformity of the plasma density of an ion source. PMID:24593593

  7. Demonstration of sawtooth period control with EC waves in KSTAR plasma

    DOE PAGESBeta

    Jeong, J. H.; Bae, Y. S.; Joung, M.; Kim, D.; Goodman, T. P.; Sauter, O.; Sakamoto, K.; Kajiwara, K.; Oda, Y.; Kwak, J. G.; et al

    2015-03-12

    The sawtooth period control in tokamak is important issue in recent years because the sawtooth crash can trigger TM/NTM instabilities and drive plasmas unstable. The control of sawtooth period by the modification of local current profile near the q=1 surface using ECCD has been demonstrated in a number of tokamaks [1, 2] including KSTAR. As a result, developing techniques to control the sawtooth period as a way of controlling the onset of NTM has been an important area of research in recent years [3]. In 2012 KSTAR plasma campaign, the sawtooth period control is carried out by the different depositionmore » position of EC waves across the q=1 surface. The sawtooth period is shortened by on-axis co-ECCD (destabilization), and the stabilization of the sawtooth is also observed by off-axis co-ECCD at outside q=1 surface. In 2013 KSTAR plasma campaign, the sawtooth locking experiment with periodic forcing of 170 GHz EC wave is carried out to control the sawtooth period. The optimal target position which lengthens the sawtooth period is investigated by performing a scan of EC beam deposition position nearby q=1 surface at the toroidal magnetic field of 2.9 T and plasma current of 0.7 MA. The sawtooth locking by the modulated EC beam is successfully demonstrated as in [3-5] with the scan of modulation-frequency and duty-ratio at the low beta (βN~0.5) plasma. In this paper, the sawteeth behavior by the location of EC beam and the preliminary result of the sawtooth locking experiments in KSTAR will be presented.« less

  8. Demonstration of sawtooth period control with EC waves in KSTAR plasma

    SciTech Connect

    Jeong, J. H.; Bae, Y. S.; Joung, M.; Kim, D.; Goodman, T. P.; Sauter, O.; Sakamoto, K.; Kajiwara, K.; Oda, Y.; Kwak, J. G.; Namkung, W.; Cho, M. H.; Park, H.; Hosea, J.; Ellis, R.

    2015-03-12

    The sawtooth period control in tokamak is important issue in recent years because the sawtooth crash can trigger TM/NTM instabilities and drive plasmas unstable. The control of sawtooth period by the modification of local current profile near the q=1 surface using ECCD has been demonstrated in a number of tokamaks [1, 2] including KSTAR. As a result, developing techniques to control the sawtooth period as a way of controlling the onset of NTM has been an important area of research in recent years [3]. In 2012 KSTAR plasma campaign, the sawtooth period control is carried out by the different deposition position of EC waves across the q=1 surface. The sawtooth period is shortened by on-axis co-ECCD (destabilization), and the stabilization of the sawtooth is also observed by off-axis co-ECCD at outside q=1 surface. In 2013 KSTAR plasma campaign, the sawtooth locking experiment with periodic forcing of 170 GHz EC wave is carried out to control the sawtooth period. The optimal target position which lengthens the sawtooth period is investigated by performing a scan of EC beam deposition position nearby q=1 surface at the toroidal magnetic field of 2.9 T and plasma current of 0.7 MA. The sawtooth locking by the modulated EC beam is successfully demonstrated as in [3-5] with the scan of modulation-frequency and duty-ratio at the low beta (βN~0.5) plasma. In this paper, the sawteeth behavior by the location of EC beam and the preliminary result of the sawtooth locking experiments in KSTAR will be presented.

  9. Observation of the intrinsic rotation in KSTAR Ohmic L-mode plasmas

    NASA Astrophysics Data System (ADS)

    Na, D. H.; Na, Yong-Su; Lee, S. G.; Angioni, C.; Yang, S. M.; Kim, H.-S.; Hahm, T. S.; Ko, W. H.; Jhang, H.; Lee, W. J.; KSTAR Team

    2016-03-01

    Two types of experiments were carried out to conduct an intrinsic rotation study in KSTAR. The first was a density ramp-up experiment without neutral beam injection, and the second was an experiment with beam blip technique. In these experiments, some characteristics of the intrinsic rotation were observed in the KSTAR Ohmic L-mode plasmas including: (i) a non-monotonic dependence of the core intrinsic rotation, called U-curve behaviour, with respect to the electron density and the collisionality related to the gradient of the toroidal rotation profile; and (ii) the behaviour of the anchor point in the intrinsic rotation profile for which the region exhibits a roughly flat shape and stays at nearly the same value even if the gradient of the toroidal rotation changes significantly in the core region. The location of the anchor point seems to be related to the q profile, and the toroidal rotation at the anchor point changes with the plasma operation parameters. These observations in the KSTAR Ohmic L-mode plasmas seem to be related to the rotation reversal phenomenon. A transport analysis was performed for the beam blip experiments in order to evaluate the intrinsic torque so that the U-curve behaviour can be further understood. The first results of the transport analysis in the KSTAR Ohmic L-mode plasmas show a correlation of the momentum fluxes and the intrinsic torques with the electron density and the collisionality. The rough magnitude and profiles of the intrinsic torque was experimentally obtained, and their possible mechanism is briefly discussed.

  10. Development of multichannel intermediate frequency system for electron cyclotron emission radiometer on KSTAR Tokamak.

    PubMed

    Kogi, Yuichiro; Sakoda, Takuya; Mase, Atsushi; Ito, Naoki; Yokota, Yuya; Yamaguchi, Soichiro; Nagayama, Yoshio; Jeong, Seung H; Kwon, Myeun; Kawahata, Kazuo

    2008-10-01

    Plasma experiments on KSTAR are scheduled to start up this year (2008). We have developed an electron cyclotron emission (ECE) radiometer to measure the radial electron temperature profiles in KSTAR experiments. The radiometer system consists, briefly, of two downconversion stages, amplifiers, bandpass filter banks, and video detectors. These components are made commercially or developed in house. The system detects ECE power in the frequency range from 110 to 196 GHz, the detected signal being resolved by means of 48 frequency windows. Before installation of this system on KSTAR, we installed a part of this system on large helical device (LHD) to study the system under similar plasma conditions. In this experiment, the signal amplitude, considered to be proportional to the electron temperature, is measured. The time-dependent traces of the electron temperature measured by this radiometer are in good agreement with those provided by the LHD Michelson spectrometer. The system noise level which limits the minimum measurable temperature (converted to the electron temperature) is about 30 eV.

  11. Development of two-grating spectrometer for the charge exchange spectroscopy system on KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, Hyungho; Song, Eun-ji; Park, Young-dong; Oh, Soo-ghee; Ko, Won-Ha

    2011-06-01

    The charge exchange spectroscopy (CES) system on Korea Superconducting Tokamak Advanced Research (KSTAR) was installed last year and had been applied to measure the C VI ion temperature and rotation velocity profiles. The ion temperature and rotation velocity profiles had been estimated from the C VI 5290.5 Å (n = 8-7) charge-exchange spectrum signal measured by a Czerny-Turner type spectrometer and a thinned back-illuminated charge coupled device (CCD) camera. However, the Czerny-Turner type spectrometer used for the KSTAR CES system showed so low signal to noise ratio for KSTAR plasmas in the 2010 experimental campaign that the time resolution of the CES system had been limited to 100 ms due to the increased exposure time of the attached CCD camera. Then, new two-grating spectrometer had been developed in order to improve the time resolution of the CES system. The spectrometer consists of two gratings (1200 g/mm and 1800 g/mm each) with additive configuration, concave mirrors (f = 50 cm), and a cylindrical lens (f = 50 cm). The time resolution of the CES system increases by a factor of 2-4 with the two-grating spectrometer. The C VI ion temperature and rotation velocity profiles obtained by the two-grating spectrometer are compared to those by Czerny-Turner type spectrometer in this paper.

  12. Numerical Simulation on Applicability of Resonant Magnetic Perturbation to KSTAR Tokamak

    NASA Astrophysics Data System (ADS)

    Kim, Doohyun; Han, Hyunsun; Kim, Ki Min; Hong, Sang Hee

    2009-11-01

    A numerical simulation is carried out to investigate the perturbed magnetic field configurations for a feasibility study on the resonant magnetic perturbation(RMP) to mitigate ELM damages to the divertor in KSTAR tokamak. The perturbed magnetic fields are described by vacuum superposition of equilibrium fields and fluctuating fields induced from the in- vessel control coils (IVCCs) will be installed in KSTAR. The equilibrium and induced fields are calculated using Grad- Shafranov equation and Biot-Savart law, respectively. For visualizing the magnetic field configurations, a field line tracing code has been developed using the 4th-order Runge-Kutta method. Magnetic field perturbations and island configurations can be found with this tracing code by describing poloidal positions of field lines as the increment of toroidal angle. And the Chirikov parameter is calculated to verify the generation of stochastic layer by overlap of magnetic islands. From this numerical work, it is confirmed that stochastic magnetic field lines are formed when the IVCC magnetic fields are generated, and the effect of RMP on KSTAR operation is discussed.

  13. Development of multichannel intermediate frequency system for electron cyclotron emission radiometer on KSTAR Tokamak

    SciTech Connect

    Kogi, Yuichiro; Sakoda, Takuya; Mase, Atsushi; Ito, Naoki; Yokota, Yuya; Yamaguchi, Soichiro; Nagayama, Yoshio; Kawahata, Kazuo; Jeong, Seung H.; Kwon, Myeun

    2008-10-15

    Plasma experiments on KSTAR are scheduled to start up this year (2008). We have developed an electron cyclotron emission (ECE) radiometer to measure the radial electron temperature profiles in KSTAR experiments. The radiometer system consists, briefly, of two downconversion stages, amplifiers, bandpass filter banks, and video detectors. These components are made commercially or developed in house. The system detects ECE power in the frequency range from 110 to 196 GHz, the detected signal being resolved by means of 48 frequency windows. Before installation of this system on KSTAR, we installed a part of this system on large helical device (LHD) to study the system under similar plasma conditions. In this experiment, the signal amplitude, considered to be proportional to the electron temperature, is measured. The time-dependent traces of the electron temperature measured by this radiometer are in good agreement with those provided by the LHD Michelson spectrometer. The system noise level which limits the minimum measurable temperature (converted to the electron temperature) is about 30 eV.

  14. Development of two-grating spectrometer for the charge exchange spectroscopy system on KSTAR

    SciTech Connect

    Lee, Hyungho; Song, Eun-ji; Oh, Soo-ghee; Park, Young-dong; Ko, Won-Ha

    2011-06-15

    The charge exchange spectroscopy (CES) system on Korea Superconducting Tokamak Advanced Research (KSTAR) was installed last year and had been applied to measure the C VI ion temperature and rotation velocity profiles. The ion temperature and rotation velocity profiles had been estimated from the C VI 5290.5 A (n = 8-7) charge-exchange spectrum signal measured by a Czerny-Turner type spectrometer and a thinned back-illuminated charge coupled device (CCD) camera. However, the Czerny-Turner type spectrometer used for the KSTAR CES system showed so low signal to noise ratio for KSTAR plasmas in the 2010 experimental campaign that the time resolution of the CES system had been limited to 100 ms due to the increased exposure time of the attached CCD camera. Then, new two-grating spectrometer had been developed in order to improve the time resolution of the CES system. The spectrometer consists of two gratings (1200 g/mm and 1800 g/mm each) with additive configuration, concave mirrors (f = 50 cm), and a cylindrical lens (f = 50 cm). The time resolution of the CES system increases by a factor of 2-4 with the two-grating spectrometer. The C VI ion temperature and rotation velocity profiles obtained by the two-grating spectrometer are compared to those by Czerny-Turner type spectrometer in this paper.

  15. Development of two-grating spectrometer for the charge exchange spectroscopy system on KSTAR.

    PubMed

    Lee, Hyungho; Song, Eun-ji; Park, Young-dong; Oh, Soo-ghee; Ko, Won-Ha

    2011-06-01

    The charge exchange spectroscopy (CES) system on Korea Superconducting Tokamak Advanced Research (KSTAR) was installed last year and had been applied to measure the C VI ion temperature and rotation velocity profiles. The ion temperature and rotation velocity profiles had been estimated from the C VI 5290.5 Å (n = 8-7) charge-exchange spectrum signal measured by a Czerny-Turner type spectrometer and a thinned back-illuminated charge coupled device (CCD) camera. However, the Czerny-Turner type spectrometer used for the KSTAR CES system showed so low signal to noise ratio for KSTAR plasmas in the 2010 experimental campaign that the time resolution of the CES system had been limited to 100 ms due to the increased exposure time of the attached CCD camera. Then, new two-grating spectrometer had been developed in order to improve the time resolution of the CES system. The spectrometer consists of two gratings (1200 g/mm and 1800 g/mm each) with additive configuration, concave mirrors (f = 50 cm), and a cylindrical lens (f = 50 cm). The time resolution of the CES system increases by a factor of 2-4 with the two-grating spectrometer. The C VI ion temperature and rotation velocity profiles obtained by the two-grating spectrometer are compared to those by Czerny-Turner type spectrometer in this paper.

  16. Stable plasma start-up in the KSTAR device under various discharge conditions

    NASA Astrophysics Data System (ADS)

    Kim, Jayhyun; Yoon, S. W.; Jeon, Y. M.; Leuer, J. A.; Eidietis, N. W.; Mueller, D.; Park, S.; Nam, Y. U.; Chung, J.; Lee, K. D.; Hahn, S. H.; Bae, Y. S.; Kim, W. C.; Oh, Y. K.; Yang, H. L.; Park, K. R.; Na, H. K.; KSTAR Team

    2011-08-01

    A time series of static nonlinear ferromagnetic calculations was performed to mimic the time-dependent modelling of plasma start-up by assessing the effects of the ferromagnetic Incoloy 908 used in the superconducting coil jackets of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. Time-series calculations of a two-dimensional axisymmetric circuit model with nonlinear ferromagnetic effects enabled us to find appropriate waveforms for the KSTAR poloidal field coil currents that satisfied various start-up requirements, such as the formation and sustainment of field nulls, a sufficient amount of magnetic flux for further plasma current ramp-up, sufficiently large Et ·Bt/Bbottom > 1 kV m-1 contours for successful breakdown, plasma current toroidal equilibria, etc. In addition to the aforementioned requirements, the results introduced in this report also provided the positional stability of the plasma current channel against radial as well as vertical perturbations by compensating the field deformation originating from the ferromagnetic effects. With the improved positional stability, robust plasma start-up was achieved during the 2010 KSTAR campaign under various discharge conditions such as the recovery process from plasma disruptions.

  17. Quantifying noise sources in the KSTAR 2014 Thomson Scattering system from the measured variation on electron temperature

    NASA Astrophysics Data System (ADS)

    Oh, T.-S.; Kim, K. H.; Lee, J. H.; Lee, S. H.; Scannell, R.; Field, A. R.; Cho, K.; Bawa'aneh, M. S.; Ghim, Y.-c.

    2016-03-01

    With the Thomson scattering (TS) system in KSTAR, temporal evolution of electron temperature (Te) is estimated using a weighted look-up table method with fast sampling (1.25 or 2.5 GS/s) digitizers during the 2014 KSTAR campaign. Background noise level is used as a weighting parameter without considering the photon noise due to the absence of information on absolute photon counts detected by the TS system. Estimated electron temperature during a relatively quiescent discharge are scattered, i.e., 15% variation on Te with respect to its mean value. We find that this 15% variation on Te cannot be explained solely by the background noise level which leads us to include photon noise effects in our analysis. Using synthetic data, we have estimated the required photon noise level consistent with the observation and determined the dominant noise source in KSTAR TS system.

  18. Microfiber-based few-layer MoS2 saturable absorber for 2.5 GHz passively harmonic mode-locked fiber laser.

    PubMed

    Liu, Meng; Zheng, Xu-Wu; Qi, You-Li; Liu, Hao; Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng; Zhao, Chu-Jun; Zhang, Han

    2014-09-22

    We reported on the generation of high-order harmonic mode-locking in a fiber laser using a microfiber-based molybdenum disulfide (MoS(2)) saturable absorber (SA). Taking advantage of both the saturable absorption and large third-order nonlinear susceptibilities of the few-layer MoS(2), up to 2.5 GHz repetition rate HML pulse could be obtained at a pump power of 181 mW, corresponding to 369th harmonic of fundamental repetition frequency. The results provide the first demonstration of the simultaneous applications of both highly nonlinear and saturable absorption effects of the MoS(2), indicating that the microfiber-based MoS(2) photonic device could serve as high-performance SA and highly nonlinear optical component for application fields such as ultrafast nonlinear optics.

  19. Dynamic characteristics of 410 nm semipolar (20 2 ¯ 1 ¯) III-nitride laser diodes with a modulation bandwidth of over 5 GHz

    NASA Astrophysics Data System (ADS)

    Lee, Changmin; Zhang, Chong; Becerra, Daniel L.; Lee, Seunggeun; Forman, Charles A.; Oh, Sang Ho; Farrell, Robert M.; Speck, James S.; Nakamura, Shuji; Bowers, John E.; DenBaars, Steven P.

    2016-09-01

    The dynamic characteristics of III-nitride multi-quantum well laser diodes (LDs) emitting at 410 nm were investigated. LDs were grown on semipolar (20 2 ¯ 1 ¯) bulk GaN substrates and fabricated into devices with cavity lengths ranging from 900 nm to 1800 nm. A 3-dB bandwidth of 5 GHz and 5 Gbit/s direct modulation with on-off keying were demonstrated, which were limited by the bandwidth of the photodetector used for the measurements. The differential gain of the LDs was determined to be 2.5 ± 0.5 × 10-16 cm2 by comparing the slope efficiency for different cavity lengths. Analysis of the frequency response showed that the K-factor, the gain compression factor, and the intrinsic maximum bandwidth were 0.33 ns, 7.4 × 10-17 cm3, and 27 GHz, respectively.

  20. Measurement of the ratio of hydrogen to deuterium at the KSTAR 2009 experimental campaign

    SciTech Connect

    Kwak, Jong-Gu; Wang, Son Jong; Kim, Sun Ho; Park, Jae Min; Na, Hoon Kyun

    2010-10-15

    The control of the ratio of hydrogen to the deuterium is one of the very important issues for ion cyclotron range of frequency (ICRF) minority heating as well as the plasma wall interaction in the tokamak. The ratio of hydrogen to deuterium during the tokamak shot was deduced from the emission spectroscopy measurements during the KSTAR 2009 experimental campaign. Graphite tiles were used for the plasma facing components (PFCs) at KSTAR and its surface area exposed to the plasma was about 11 m{sup 2}. The data showed that it remained as high as around 50% during the campaign period because graphite tiles were exposed to the air for about two months and the hydrogen contents at the tiles are not fully pumped out due to the lack of baking on the PFC in the 2009 campaign. The validation of the spectroscopy method was checked by using the Zeeman effects and the ratio of hydrogen to the deuterium is compared with results from the residual gas analysis. During the tokamak shot, the ratio is low below 10% initially and saturated after around 1 s. When there is a hydrogen injection to the vessel via ion cyclotron wall conditioning and the boronization process where the carbone is used, the ratio of the hydrogen to the deuterium is increased by up to 100% and it recovers to around 50% after one day of operation. However it does not decrease below 50% at the end of the experimental campaign. It was found that the full baking on the PFC (with a high temperature and sufficient vacuum pumping) is required for the ratio control which guarantees the efficient ICRF heating at the KSTAR 2010 experimental campaign.

  1. Multiple toroidal Alfven eigenmodes with a single toroidal mode number in KSTAR plasmas

    NASA Astrophysics Data System (ADS)

    Rizvi, H.; Ryu, C. M.; Lin, Z.

    2016-11-01

    Simultaneous excitation of multiple discrete toroidal Alfven eigenmodes (TAEs) for a single toroidal mode number have been observed in KSTAR plasmas. Excitation and characteristics of these modes are studied by using a global gyrokinetic particle-in-cell simulation code. It is shown that compared to a single core-localized mode, excitation of two modes is difficult. The frequency difference between the double TAEs studied from simulation seems to agree well with the experimental value. Details of studies on the frequency, growth rate, mode structures, etc, using the GTC simulation are presented.

  2. Test of prototype ITER vacuum ultraviolet spectrometer and its application to impurity study in KSTAR plasmas.

    PubMed

    Seon, C R; Hong, J H; Jang, J; Lee, S H; Choe, W; Lee, H H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

    2014-11-01

    To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a prototype VUV spectrometer was developed. The sensitivity calibration curve of the spectrometer was calculated from the mirror reflectivity, the grating efficiency, and the detector efficiency. The calibration curve was consistent with the calibration points derived in the experiment using the calibrated hollow cathode lamp. For the application of the prototype ITER VUV spectrometer, the prototype spectrometer was installed at KSTAR, and various impurity emission lines could be measured. By analyzing about 100 shots, strong positive correlation between the O VI and the C IV emission intensities could be found.

  3. Test of prototype ITER vacuum ultraviolet spectrometer and its application to impurity study in KSTAR plasmas.

    PubMed

    Seon, C R; Hong, J H; Jang, J; Lee, S H; Choe, W; Lee, H H; Cheon, M S; Pak, S; Lee, H G; Biel, W; Barnsley, R

    2014-11-01

    To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a prototype VUV spectrometer was developed. The sensitivity calibration curve of the spectrometer was calculated from the mirror reflectivity, the grating efficiency, and the detector efficiency. The calibration curve was consistent with the calibration points derived in the experiment using the calibrated hollow cathode lamp. For the application of the prototype ITER VUV spectrometer, the prototype spectrometer was installed at KSTAR, and various impurity emission lines could be measured. By analyzing about 100 shots, strong positive correlation between the O VI and the C IV emission intensities could be found. PMID:25430310

  4. Design of the Collective Thomson scattering (CTS) system by using 170-GHz gyrotron in the KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Min; Kim, Sun-Ho; Kim, Sung-Kyu; Lee, Kyu-Dong; Wang, Son-Jong

    2014-10-01

    The physics of energetic ions is one of the primary subjects to be understood toward the realization of a nuclear fusion power plant. Collective Thomson scattering (CTS) offers the possibility to diagnose the fast ions and the alpha particles in burning plasmas. Spatially- and temporally-resolved one-dimensional velocity distributions of the fast ions can be obtained from the scattered radiation with fewer geometric constraints by utilizing millimeter waves from a high-power gyrotron as a probe beam. We studied the feasibility of CTS fast-ion measurements in the KSTAR by calculating the spectral density functions. Based on that, we suggest a design for the CTS system that uses the currently-operating 170-GHz gyrotron for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) in the KSTAR. The CTS system is presented as two subsystems: the antenna system and the heterodyne receiver system. The design procedure for an off-axis ellipsoidal mirror is described, and the CTS system requirements are discussed.

  5. Operating characteristics of a new ion source for KSTAR neutral beam injection system

    SciTech Connect

    Kim, Tae-Seong Jeong, Seung Ho; Chang, Doo-Hee; Lee, Kwang Won; In, Sang-Ryul

    2014-02-15

    A new positive ion source for the Korea Superconducting Tokamak Advanced Research neutral beam injection (KSTAR NBI-1) system was designed, fabricated, and assembled in 2011. The characteristics of the arc discharge and beam extraction were investigated using hydrogen and helium gas to find the optimum operating parameters of the arc power, filament voltage, gas pressure, extracting voltage, accelerating voltage, and decelerating voltage at the neutral beam test stand at the Korea Atomic Energy Research Institute in 2012. Based on the optimum operating condition, the new ion source was then conditioned, and performance tests were primarily finished. The accelerator system with enlarged apertures can extract a maximum 65 A ion beam with a beam energy of 100 keV. The arc efficiency and optimum beam perveance, at which the beam divergence is at a minimum, are estimated to be 1.0 A/kW and 2.5 uP, respectively. The beam extraction tests show that the design goal of delivering a 2 MW deuterium neutral beam into the KSTAR Tokamak plasma is achievable.

  6. Operating characteristics of a new ion source for KSTAR neutral beam injection system

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Seong; Jeong, Seung Ho; Chang, Doo-Hee; Lee, Kwang Won; In, Sang-Ryul

    2014-02-01

    A new positive ion source for the Korea Superconducting Tokamak Advanced Research neutral beam injection (KSTAR NBI-1) system was designed, fabricated, and assembled in 2011. The characteristics of the arc discharge and beam extraction were investigated using hydrogen and helium gas to find the optimum operating parameters of the arc power, filament voltage, gas pressure, extracting voltage, accelerating voltage, and decelerating voltage at the neutral beam test stand at the Korea Atomic Energy Research Institute in 2012. Based on the optimum operating condition, the new ion source was then conditioned, and performance tests were primarily finished. The accelerator system with enlarged apertures can extract a maximum 65 A ion beam with a beam energy of 100 keV. The arc efficiency and optimum beam perveance, at which the beam divergence is at a minimum, are estimated to be 1.0 A/kW and 2.5 uP, respectively. The beam extraction tests show that the design goal of delivering a 2 MW deuterium neutral beam into the KSTAR Tokamak plasma is achievable.

  7. Fast ion loss associated with perturbed field by resonant magnetic perturbation coils in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, Jun Young; Kim, Junghee; Rhee, Tongnyeol; Yoon, S. W.; Park, G. Y.; Jeon, Y. M.; Isobe, M.; Shimizu, A.; Ogawa, K.; Park, J.-K.; Garcia-Munoz, M.

    2013-10-01

    Resonant magnetic perturbation (RMP) is the most promising strategies for ELM mitigation/suppression. However, it has been found through the modeling and the experiments that RMP for the ELM mitigation can enhance the toroidally localized fast ion loss. During KSTAR experimental campaigns in 2011 and 2012, sudden increase or decrease of the fast ion loss has been observed by the scintillator-based fast ion loss detector (FILD) when the RMP is applied. Three-dimensional perturbed magnetic field by RMP coil in vacuum is calculated by Biot-Savart's law embedded in the Lorentz orbit code (LORBIT). The LORBIT code which is based on gyro-orbit following motion has been used for the simulation of the three-dimensional fast ion trajectories in presence of non-axisymmetric magnetic perturbation. It seems the measured fast ion loss rate at the localized position depends on not only the RMP field configuration but also the plasma profile such as safety factor and so on, varying the ratio between radial drift and stochastization of the fat-ion orbits. The simulation results of fast ion orbit under magnetic perturbation w/ and w/o plasma responses will be presented and compared with KSTAR FILD measurement results in various cases.

  8. Assessment and modification of an ion source grid design in KSTAR neutral beam system.

    PubMed

    Lee, Dong Won; Shin, Kyu In; Jin, Hyung Gon; Choi, Bo Guen; Kim, Tae-Seong; Jeong, Seung Ho

    2014-02-01

    A new 2 MW NB (Neutral Beam) ion source for supplying 3.5 MW NB heating for the KSTAR campaign was developed in 2012 and its grid was made from OFHC (Oxygen Free High Conductivity) copper with rectangular cooling channels. However, the plastic deformation such as a bulging in the plasma grid of the ion source was found during the overhaul period after the 2012 campaign. A thermal-hydraulic and a thermo-mechanical analysis using the conventional code, ANSYS, were carried out and the thermal fatigue life assessment was evaluated. It was found that the thermal fatigue life of the OFHC copper grid was about 335 cycles in case of 0.165 MW/m(2) heat flux and it gave too short fatigue life to be used as a KSTAR NB ion source grid. To overcome the limited fatigue life of the current design, the following methods were proposed in the present study: (1) changing the OHFC copper to CuCrZr, copper-alloy or (2) adopting a new design with a pure Mo metal grid and CuCrZr tubes. It is confirmed that the proposed methods meet the requirements by performing the same assessment. PMID:24593583

  9. First Trial of Real-time Poloidal Beta Control in KSTAR

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; Hahn, S. H.; Bak, J. G.; Walker, M. L.; Woo, M. H.; Kim, J. S.; Kim, Y. J.; Bae, Y. S.; KSTAR Team

    2014-10-01

    Sustaining the plasma in a stable and a high performance condition is one of the important control issues for future steady state tokamaks. In the 2014 KSTAR campaign, we have developed a real-time poloidal beta (βp) control technique and carried out preliminary experiments to identify its feasibility. In the control system, the βp is calculated in real time using the measured diamagnetic loop signal (DLM03) with coil pickup corrections, and compared with the target value leading to the change of the neutral beam (NB) heating power using a feedback PID control algorithm. To match the required power of NB which is operated with constant voltage, the duty cycles of the modulation were adjusted as the ratio of the required power to the maximum achievable one. This paper will present the overall procedures of the βp control, the βp estimation process implemented in the plasma control system, and the analysis on the preliminary experimental results. This work is supported by the KSTAR research project funded by the Ministry of Science, ICT & Future Planning of Korea.

  10. Design of a collective scattering system for electron gyroscale turbulence study in KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, Woochang; Park, Hyeon; Lee, Dongjae; Leem, Juneeok; Nam, Yongun

    2015-11-01

    The design characteristics of a multi-channel collective (or coherent) scattering system for electron scale turbulence study in KSTAR, which is planned to be installed in 2016, are investigated. A few critical issues are discussed in depth such as effect of the Faraday rotation of the electric field polarization of probing and scattered, the probing wave frequency which is related to the optics for measurement of electron gyro scale turbulence, the wave polarization to minimize absorption of the probing power by electron cyclotron resonant layers, and the probing power. A proper and feasible optics with 300 GHz probing wave, which is based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wave numbers up to 21 cm-1. The upper limit corresponds to the normalized wave number k⊥ρe of 0.2 in KSTAR plasmas. To detect scattered wave power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed. Work supported by NRF Korea under grant numbers NRF-2015M1A7A1A02002627 and NRF-2014M1A7A1A03029865.

  11. 4 Kelvin Cryogenic Characterization of Commercial pHEMT Transistors at 9 kHz to 8.5 GHz Range

    NASA Astrophysics Data System (ADS)

    Ibarra-Medel, E.; Velázquez, M.; Ventura, S.; Ferrusca, D.; Gómez-Rivera, V.

    2016-07-01

    Nowadays, the technology innovations in large format array detectors at low temperature for millimetric observational astronomy demand the development of electronics capable to keep their functionality at cryogenic temperatures. In kinetic inductance detectors, the first stage of electronics readout requires high-bandwidth low-noise amplifiers (LNAs). These devices are commonly fabricated in monolithic microwave integrated circuit (MMIC) processes which commercially achieve a noise temperature level of 5 K. An alternative approach to the MMIC are the hybrid microwave circuit which mixes RF lumped elements and discrete electronic components. This paper describes the characterization of six commercial pHEMT transistors tested at cryogenic temperatures. DC properties such as I-V curves and transconductance (g_m) were measured for each transistor; these measurements allow us to calculate the best bias point versus gain, with the lowest noise figure and power consumption within the range of 9 kHz to 8.5 GHz at the operating temperature of 4 K. Experimental results suggest that the characterized pHEMTs have a noise figure that allow them to be used in hybrid LNAs arranges with a comparable MMIC performance.

  12. A Search for CMB Decrements Towards Distant Cluster Candidates PC 1643+4631 and VLA 1312+4237 at 28.5 GHz

    NASA Technical Reports Server (NTRS)

    Holzapfel, W. L.; Carlstrom, J. E.; Grego, L.; Reese, E. D.; Joy, M.

    2000-01-01

    Recently, Jones et al. used the Ryle telescope, operating at a frequency of 15 GHz, to detect a flux decrement in the direction of the quasar pair PC 1643+461A,B. They interpreted this signal as the Sunyaev-Zel'dovich effect (SZE) produced by a distant cluster of galaxies. In the course of an effort to measure CMB anisotropies using the VLA at 8.4 GHz, Richards et al. (1997) detected a similar, but smaller, decrement which we refer to as VLA 1312+4237. They also proposed that this signal might be explained as the SZE signal of a distant galaxy cluster. We report observations in the direction of these claimed sources with the Berkeley Illinois Maryland Association (BIMA) interferometer operating at 28.5 GHz. We find no evidence for SZE emission in the direction of either of the claimed sources. In the case of PC 1643+4631, the BIMA data are inconsistent with the cluster emission model proposed by Jones et al. at greater than 99.99% confidence. Together with published x-ray and optical searches, these results make a compelling case against the existence of a massive cluster in the direction of PC 1643+4631. Because of the different scales to which the VLA and BIMA instruments are sensitive, the BIMA observations are not as constraining for the VLA 1312+4237 source. The BIMA data are inconsistent with the cluster model proposed by Richards et al. (1997) at approximately 80% confidence.

  13. Direct generation of 12.5-GHz-spaced optical frequency comb with ultrabroad coverage in near-infrared region by cascaded fiber configuration.

    PubMed

    Kashiwagi, Ken; Kurokawa, Takashi; Okuyama, Yasushi; Mori, Takahiro; Tanaka, Yosuke; Yamamoto, Yoshinori; Hirano, Masaaki

    2016-04-18

    We generated a 12.5-GHz-spacing optical frequency comb that can be resolved over 100 THz, from 1040 to 1750 nm, without spectral mode filtering. To cover such a broad spectrum, we used electro-optic modulation of single frequency light and line-by-line pulse synthesis to produce a clear pulse train and subsequent spectral broadening in highly nonlinear fibers (HNLFs). We numerically and experimentally investigated a configuration of the HNLFs and find that a two-stage broadening through different HNLFs is required when using limited pulse energy at a high repetition rate. We designed and fabricated solid silica-based HNLFs with small zero-dispersion wavelengths to obtain strong spectral broadening, especially at the shorter wavelengths. The individual lines of the proposed frequency comb are resolvable with high contrast over the entire spectral range. The results described in this paper should lead to the development of multicarrier sources for wavelength-division-multiplexing communication and super-multi-point frequency calibration for spectrometers, especially in astrophysics. PMID:27137251

  14. 47 CFR 25.250 - Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. 25.250 Section 25.250 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  15. 47 CFR 25.250 - Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. 25.250 Section 25.250 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  16. 47 CFR 25.250 - Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. 25.250 Section 25.250 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  17. 47 CFR 25.250 - Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. 25.250 Section 25.250 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  18. 47 CFR 25.250 - Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. 25.250 Section 25.250 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards §...

  19. Development of KSTAR ECE imaging system for measurement of temperature fluctuations and edge density fluctuations

    SciTech Connect

    Yun, G. S.; Lee, W.; Choi, M. J.; Kim, J. B.; Park, H. K.; Domier, C. W.; Tobias, B.; Liang, T.; Kong, X.; Luhmann, N. C. Jr.; Donne, A. J. H.

    2010-10-15

    The ECE imaging (ECEI) diagnostic tested on the TEXTOR tokamak revealed the sawtooth reconnection physics in unprecedented detail, including the first observation of high-field-side crash and collective heat transport [H. K. Park, N. C. Luhmann, Jr., A. J. H. Donneet al., Phys. Rev. Lett. 96, 195003 (2006)]. An improved ECEI system capable of visualizing both high- and low-field sides simultaneously with considerably better spatial coverage has been developed for the KSTAR tokamak in order to capture the full picture of core MHD dynamics. Direct 2D imaging of other MHD phenomena such as tearing modes, edge localized modes, and even Alfven eigenmodes is expected to be feasible. Use of ECE images of the optically thin edge region to recover 2D electron density changes during L/H mode transitions is also envisioned, providing powerful information about the underlying physics. The influence of density fluctuations on optically thin ECE is discussed.

  20. Development of KSTAR ECE imaging system for measurement of temperature fluctuations and edge density fluctuationsa)

    NASA Astrophysics Data System (ADS)

    Yun, G. S.; Lee, W.; Choi, M. J.; Kim, J. B.; Park, H. K.; Domier, C. W.; Tobias, B.; Liang, T.; Kong, X.; Luhmann, N. C.; Donné, A. J. H.

    2010-10-01

    The ECE imaging (ECEI) diagnostic tested on the TEXTOR tokamak revealed the sawtooth reconnection physics in unprecedented detail, including the first observation of high-field-side crash and collective heat transport [H. K. Park, N. C. Luhmann, Jr., A. J. H. Donné et al., Phys. Rev. Lett. 96, 195003 (2006)]. An improved ECEI system capable of visualizing both high- and low-field sides simultaneously with considerably better spatial coverage has been developed for the KSTAR tokamak in order to capture the full picture of core MHD dynamics. Direct 2D imaging of other MHD phenomena such as tearing modes, edge localized modes, and even Alfvén eigenmodes is expected to be feasible. Use of ECE images of the optically thin edge region to recover 2D electron density changes during L/H mode transitions is also envisioned, providing powerful information about the underlying physics. The influence of density fluctuations on optically thin ECE is discussed.

  1. Innovations in optical coupling of the KSTAR electron cyclotron emission imaging diagnostic

    SciTech Connect

    Liang, T.; Tobias, B.; Kong, X.; Domier, C. W.; Luhmann, N. C. Jr.; Lee, W.; Yun, G. S.; Park, H. K.

    2010-10-15

    The installation of a new electron cyclotron emission imaging diagnostic for the Korea Superconducting Tokamak Advanced Research (KSTAR) is underway, making use of a unique optical port cassette design, which allows placement of refractive elements inside the cryostat region without adverse effects. The result is unprecedented window access for the implementation of a state of the art imaging diagnostic. A dual-array optical design has been developed, capable of simultaneously imaging the high and low field sides of the plasma with independent features of focal plane translation, vertical zoom, and radial channel spacing. The number of translating optics has been minimized by making use of a zoom lens triplet and parabolic plasma facing lens for maximum channel uniformity over a continuous vertical zoom range of 3:1. The simulated performance of this design is presented along with preliminary laboratory characterization data.

  2. Data acquisition and processing system of the electron cyclotron emission imaging system of the KSTAR tokamak

    SciTech Connect

    Kim, J. B.; Lee, W.; Yun, G. S.; Park, H. K.; Domier, C. W.; Luhmann, N. C. Jr.

    2010-10-15

    A new innovative electron cyclotron emission imaging (ECEI) diagnostic system for the Korean Superconducting Tokamak Advanced Research (KSTAR) produces a large amount of data. The design of the data acquisition and processing system of the ECEI diagnostic system should consider covering the large data production and flow. The system design is based on the layered structure scalable to the future extension to accommodate increasing data demands. Software architecture that allows a web-based monitoring of the operation status, remote experiment, and data analysis is discussed. The operating software will help machine operators and users validate the acquired data promptly, prepare next discharge, and enhance the experiment performance and data analysis in a distributed environment.

  3. Innovations in optical coupling of the KSTAR electron cyclotron emission imaging diagnostic.

    PubMed

    Liang, T; Tobias, B; Kong, X; Domier, C W; Luhmann, N C; Lee, W; Yun, G S; Park, H K

    2010-10-01

    The installation of a new electron cyclotron emission imaging diagnostic for the Korea Superconducting Tokamak Advanced Research (KSTAR) is underway, making use of a unique optical port cassette design, which allows placement of refractive elements inside the cryostat region without adverse effects. The result is unprecedented window access for the implementation of a state of the art imaging diagnostic. A dual-array optical design has been developed, capable of simultaneously imaging the high and low field sides of the plasma with independent features of focal plane translation, vertical zoom, and radial channel spacing. The number of translating optics has been minimized by making use of a zoom lens triplet and parabolic plasma facing lens for maximum channel uniformity over a continuous vertical zoom range of 3:1. The simulated performance of this design is presented along with preliminary laboratory characterization data.

  4. Investigation of SOL parameters and divertor particle flux from electric probe measurements in KSTAR

    NASA Astrophysics Data System (ADS)

    Bak, J. G.; Kim, H. S.; Bae, M. K.; Juhn, J. W.; Seo, D. C.; Bang, E. N.; Shim, S. B.; Chung, K. S.; Lee, H. J.; Hong, S. H.

    2015-08-01

    The upstream scrape-off layer (SOL) profiles and downstream particle fluxes are measured with a fast reciprocating Langmuir probe assembly (FRLPA) at the outboard mid-plane and a fixed edge Langmuir probe array (ELPA) at divertor region, respectively in the KSTAR. It is found that the SOL has a two-layer structure in the outboard wall-limited (OWL) ohmic and L-mode: a near SOL (∼5 mm zone) with a narrow feature and a far SOL with a broader profile. The near SOL width evaluated from the SOL profiles in the OWL plasmas is comparable to the scaling for the L-mode divertor plasmas in the JET and AUG. In the SOL profiles and the divertor particle flux profile during the ELMy H-modes, the characteristic e-folding lengths of electron temperature, plasma density and particle flux during an ELM phase are about two times larger than ones at the inter ELM.

  5. Measurements of internal magnetic structures from neutral beam emission spectra in KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, J.; Chung, J.; Song, M.; You, K. I.

    2012-10-01

    The magnetic pitch angle and the magnitude from magnetically confined fusion devices are measured by fitting the beam emission spectra under the motional Stark effect (MSE). Initial values for the free parameters in the complicated raw spectra are obtained from and constrained by the MSE model in the Atomic Data and Analysis Structure (ADAS) which uses a collisional-radiative model with level populations nlm-resolved up to n = 4 and a simple born approximation for ion-impact cross sections. This technique is examined for the MSE spectra taken from the KSTAR plasma discharges and its validity and applicability are discussed to directly infer the internal magnetic field structure with a wide range of pitch angles. The sensitivity of EFIT reconstruction on these internal magnetic data is also discussed.

  6. Study on the heat flux reconstruction with the infrared thermography for the divertor target plates in the KSTAR tokamak.

    PubMed

    Kang, C S; Lee, H H; Oh, S; Lee, S G; Wi, H M; Kim, Y S; Kim, H S

    2016-08-01

    An infrared (IR) thermography is the preferred diagnostic that can quantify heat flux by measuring the surface temperature distributions of the divertor plates. The IR thermography is successfully instrumented on Korea Superconducting Tokamak Advanced Research (KSTAR). In this study, finite volume method is considered to solve the heat conduction equations. 1D-, 2D-, and 3D models are developed and compared with various calculation algorithms, such as Duhamel's theorem and THEODOR. These comparisons show good agreement. In order to acquire more efficient and reliable calculation results, we consider two numerical analysis schemes, influence of temperature on thermal properties and image stabilization. Recently, this reconstruction code is successfully applied to the KSTAR IR thermography. PMID:27587124

  7. Study on the heat flux reconstruction with the infrared thermography for the divertor target plates in the KSTAR tokamak.

    PubMed

    Kang, C S; Lee, H H; Oh, S; Lee, S G; Wi, H M; Kim, Y S; Kim, H S

    2016-08-01

    An infrared (IR) thermography is the preferred diagnostic that can quantify heat flux by measuring the surface temperature distributions of the divertor plates. The IR thermography is successfully instrumented on Korea Superconducting Tokamak Advanced Research (KSTAR). In this study, finite volume method is considered to solve the heat conduction equations. 1D-, 2D-, and 3D models are developed and compared with various calculation algorithms, such as Duhamel's theorem and THEODOR. These comparisons show good agreement. In order to acquire more efficient and reliable calculation results, we consider two numerical analysis schemes, influence of temperature on thermal properties and image stabilization. Recently, this reconstruction code is successfully applied to the KSTAR IR thermography.

  8. Study on the heat flux reconstruction with the infrared thermography for the divertor target plates in the KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Kang, C. S.; Lee, H. H.; Oh, S.; Lee, S. G.; Wi, H. M.; Kim, Y. S.; Kim, H. S.

    2016-08-01

    An infrared (IR) thermography is the preferred diagnostic that can quantify heat flux by measuring the surface temperature distributions of the divertor plates. The IR thermography is successfully instrumented on Korea Superconducting Tokamak Advanced Research (KSTAR). In this study, finite volume method is considered to solve the heat conduction equations. 1D-, 2D-, and 3D models are developed and compared with various calculation algorithms, such as Duhamel's theorem and THEODOR. These comparisons show good agreement. In order to acquire more efficient and reliable calculation results, we consider two numerical analysis schemes, influence of temperature on thermal properties and image stabilization. Recently, this reconstruction code is successfully applied to the KSTAR IR thermography.

  9. Synchronized operation by field programmable gate array based signal controller for the Thomson scattering diagnostic system in KSTAR

    SciTech Connect

    Lee, W. R.; Park, M. K.; Lee, J. H.; Kim, H. S.; Kim, K. H.

    2012-09-15

    The Thomson scattering diagnostic system is successfully installed in the Korea Superconducting Tokamak Advanced Research (KSTAR) facility. We got the electron temperature and electron density data for the first time in 2011, 4th campaign using a field programmable gate array (FPGA) based signal control board. It operates as a signal generator, a detector, a controller, and a time measuring device. This board produces two configurable trigger pulses to operate Nd:YAG laser system and receives a laser beam detection signal from a photodiode detector. It allows a trigger pulse to be delivered to a time delay module to make a scattered signal measurement, measuring an asynchronous time value between the KSTAR timing board and the laser system injection signal. All functions are controlled by the embedded processor running on operating system within a single FPGA. It provides Ethernet communication interface and is configured with standard middleware to integrate with KSTAR. This controller has operated for two experimental campaigns including commissioning and performed the reconfiguration of logic designs to accommodate varying experimental situation without hardware rebuilding.

  10. KSTAR Equilibrium Operating Space and Projected Stabilization at High Normalized Beta

    SciTech Connect

    Park, Y. S.; Sabbagh, S. A.; Berkery, J.W.; Bialek, J.; Jeon, Y. M.; Hahn, S. H.; Eidietis, N. W.; Evans, T. E.; Yoon, S. W.; Ahn, Joonwook; Kim, J.; Yang, H. L.; You, K. I.; Soukhanovskii, V. A.; Bae, Y. S.; Chung, J. I.; Kwon, M.; Oh, Y. K.; Kim, W. C.; Kim, J. Y.; Lee, S. G.; Park, H.; Reimerdes, H.; Leuer, J. A.; Walker, M. L.

    2011-01-01

    Along with an expanded evaluation of the equilibrium operating space of the Korea Superconducting Tokamak Advanced Research, KSTAR, experimental equilibria of the most recent plasma discharges were reconstructed using the EFIT code. In near-circular plasmas created in 2009, equilibria reached a stored energy of 54 kJ with a maximum plasma current of 0.34 MA. Highly shaped plasmas with near double-null configuration in 2010 achieved H-mode with clear edge localized mode (ELM) activity, and transiently reached a stored energy of up to 257 kJ, elongation of 1.96 and normalized beta of 1.3. The plasma current reached 0.7 MA. Projecting active and passive stabilization of global MHD instabilities for operation above the ideal no-wall beta limit using the designed control hardware was also considered. Kinetic modification of the ideal MHD n = 1 stability criterion was computed by the MISK code on KSTAR theoretical equilibria with a plasma current of 2 MA, internal inductance of 0.7 and normalized beta of 4.0 with simple density, temperature and rotation profiles. The steep edge pressure gradient of this equilibrium resulted in the need for significant plasma toroidal rotation to allow thermal particle kinetic resonances to stabilize the resistive wall mode (RWM). The impact of various materials and electrical connections of the passive stabilizing plates on RWM growth rates was analysed, and copper plates reduced the RWM passive growth rate by a factor of 15 compared with stainless steel plates at a normalized beta of 4.4. Computations of active RWM control using the VALEN code showed that the n = 1 mode can be stabilized at normalized beta near the ideal wall limit via control fields produced by the midplane in-vessel control coils (IVCCs) with as low as 0.83kW control power using ideal control system assumptions. The ELM mitigation potential of the IVCC, examined by evaluating the vacuum island overlap created by resonant magnetic perturbations, was analysed using the

  11. Investigation of MHD instabilities and control in KSTAR preparing for high beta operation

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Bialek, J. M.; Berkery, J. W.; Lee, S. G.; Ko, W. H.; Bak, J. G.; Jeon, Y. M.; Park, J. K.; Kim, J.; Hahn, S. H.; Ahn, J.-W.; Yoon, S. W.; Lee, K. D.; Choi, M. J.; Yun, G. S.; Park, H. K.; You, K.-I.; Bae, Y. S.; Oh, Y. K.; Kim, W.-C.; Kwak, J. G.

    2013-08-01

    Initial H-mode operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) is expanded to higher normalized beta and lower plasma internal inductance moving towards design target operation. As a key supporting device for ITER, an important goal for KSTAR is to produce physics understanding of MHD instabilities at long pulse with steady-state profiles, at high normalized beta, and over a wide range of plasma rotation profiles. An advance from initial plasma operation is a significant increase in plasma stored energy and normalized beta, with Wtot = 340 kJ, βN = 1.9, which is 75% of the level required to reach the computed ideal n = 1 no-wall stability limit. The internal inductance was lowered to 0.9 at sustained H-mode duration up to 5 s. In ohmically heated plasmas, the plasma current reached 1 MA with prolonged pulse length up to 12 s. Rotating MHD modes are observed in the device with perturbations having tearing rather than ideal parity. Modes with m/n = 3/2 are triggered during the H-mode phase but are relatively weak and do not substantially reduce Wtot. In contrast, 2/1 modes to date only appear when the plasma rotation profiles are lowered after H-L back-transition. Subsequent 2/1 mode locking creates a repetitive collapse of βN by more than 50%. Onset behaviour suggests the 3/2 mode is close to being neoclassically unstable. A correlation between the 2/1 mode amplitude and local rotation shear from an x-ray imaging crystal spectrometer suggests that the rotation shear at the mode rational surface is stabilizing. As a method to access the ITER-relevant low plasma rotation regime, plasma rotation alteration by n = 1, 2 applied fields and associated neoclassical toroidal viscosity (NTV) induced torque is presently investigated. The net rotation profile change measured by a charge exchange recombination diagnostic with proper compensation of plasma boundary movement shows initial evidence of non-resonant rotation damping by the n = 1, 2 applied

  12. Conceptual Design Studies of the KSTAR Bay-Nm Cassette and Thomson Scattering Optics

    SciTech Connect

    Feder, R.; Ellis, R.; Johnson, D.; Park, H.; Lee, H. G.

    2005-09-26

    A Multi-Channel Thomson Scattering System viewing the edge and core of the KSTAR plasma will be installed at the mid-plane port Bay-N. An engineering design study was undertaken at PPPL in collaboration with the Korea Basic Science Institute (KBSI) to determine the optimal optics and cassette design. Design criteria included environmental, mechanical and optical factors. All of the optical design options have common design features; the Thomson Scattering laser, an in-vacuum shutter, a quartz heat shield and primary vacuum window, a set of optical elements and a fiber optic bundle. Neutron radiation damage was a major factor in the choice of competing lens-based and mirror-based optical designs. Both the mirror based design and the lens design are constrained by physical limits of the Bay-N cassette and interference with the Bay-N micro-wave launcher. The cassette will contain the optics and a rail system for maintenance of the optics.

  13. ECH effects on toroidal rotation: KSTAR experiments, intrinsic torque modelling and gyrokinetic stability analyses

    NASA Astrophysics Data System (ADS)

    Shi, Y. J.; Ko, W. H.; Kwon, J. M.; Diamond, P. H.; Lee, S. G.; Ko, S. H.; Wang, L.; Yi, S.; Ida, K.; Terzolo, L.; Yoon, S. W.; Lee, K. D.; Lee, J. H.; Nam, U. N.; Bae, Y. S.; Oh, Y. K.; Kwak, J. G.; Bitter, M.; Hill, K.; Gurcan, O. D.; Hahm, T. S.

    2013-11-01

    Toroidal rotation profiles have been investigated in KSTAR H-mode plasma using combined auxiliary heating by co-neutral beam injection (NBI) and electron cyclotron resonance heating (ECH). The ion temperature and toroidal rotation are measured with x-ray imaging crystal spectroscopy and charge exchange recombination spectroscopy. H-mode plasma is achieved using co-current 1.3 MW NBI, and a 0.35 MW ECH pulse is added to the flat-top of H-mode. The core rotation profiles, which are centrally peaked in the pure NBI heating phase, flatten when ECH is injected, while the edge pedestal is unchanged. Dramatic decreases in the core toroidal rotation values (ΔVtor/Vtor ˜ -30%) are observed when on-axis ECH is added to H-mode. The experimental data show that the decrease of core rotation velocity and its gradient are correlated with the increase of core electron temperature and its gradient, and also with the likely steepening of the density gradient. We thus explore the viability of a hypothesized ITG (ITG ion temperature gradient instability) → TEM (trapped electron mode instability) transition as the explanation of the observed counter-current flow induced by ECH. However, the results of linear microstability analyses using inferred profiles suggest that the TEM is excited only in the deep core, so the viability of the hypothesized explanation is not yet clear.

  14. Radiation damage of the PCO Pixelfly VGA CCD camera of the BES system on KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Náfrádi, Gábor; Kovácsik, Ákos; Pór, Gábor; Lampert, Máté; Un Nam, Yong; Zoletnik, Sándor

    2015-01-01

    A PCO Pixelfly VGA CCD camera which is part a of the Beam Emission Spectroscopy (BES) diagnostic system of the Korea Superconducting Tokamak Advanced Research (KSTAR) used for spatial calibrations, suffered from serious radiation damage, white pixel defects have been generated in it. The main goal of this work was to identify the origin of the radiation damage and to give solutions to avoid it. Monte Carlo N-Particle eXtended (MCNPX) model was built using Monte Carlo Modeling Interface Program (MCAM) and calculations were carried out to predict the neutron and gamma-ray fields in the camera position. Besides the MCNPX calculations pure gamma-ray irradiations of the CCD camera were carried out in the Training Reactor of BME. Before, during and after the irradiations numerous frames were taken with the camera with 5 s long exposure times. The evaluation of these frames showed that with the applied high gamma-ray dose (1.7 Gy) and dose rate levels (up to 2 Gy/h) the number of the white pixels did not increase. We have found that the origin of the white pixel generation was the neutron-induced thermal hopping of the electrons which means that in the future only neutron shielding is necessary around the CCD camera. Another solution could be to replace the CCD camera with a more radiation tolerant one for example with a suitable CMOS camera or apply both solutions simultaneously.

  15. Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system

    SciTech Connect

    Lee, J.; Yun, G. S. Lee, J. E.; Kim, M.; Choi, M. J.; Lee, W.; Park, H. K.; Domier, C. W.; Luhmann, N. C.; Sabbagh, S. A.; Park, Y. S.; Lee, S. G.; Bak, J. G.

    2014-06-15

    A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α{sub *} of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α{sub *} is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.

  16. 4C code analysis of thermal-hydraulic transients in the KSTAR PF1 superconducting coil

    NASA Astrophysics Data System (ADS)

    Savoldi Richard, L.; Bonifetto, R.; Chu, Y.; Kholia, A.; Park, S. H.; Lee, H. J.; Zanino, R.

    2013-01-01

    The KSTAR tokamak, in operation since 2008 at the National Fusion Research Institute in Korea, is equipped with a full superconducting magnet system including the central solenoid (CS), which is made of four symmetric pairs of coils PF1L/U-PF4L/U. Each of the CS coils is pancake wound using Nb3Sn cable-in-conduit conductors with a square Incoloy jacket. The coils are cooled with supercritical He in forced circulation at nominal 4.5 K and 5.5 bar inlet conditions. During different test campaigns the measured temperature increase due to AC losses turned out to be higher than expected, which motivates the present study. The 4C code, already validated against and applied to different types of thermal-hydraulic transients in different superconducting coils, is applied here to the thermal-hydraulic analysis of a full set of trapezoidal current pulses in the PF1 coils, with different ramp rates. We find the value of the coupling time constant nτ that best fits, at each current ramp rate, the temperature increase up to the end of the heating at the coil outlet. The agreement between computed results and the whole set of measured data, including temperatures, pressures and mass flow rates, is then shown to be very good both at the inlet and at the outlet of the coil. The nτ values needed to explain the experimental results decrease at increasing current ramp rates, consistently with the results found in the literature.

  17. Intelligence System for Diagnosis Level of Coronary Heart Disease with K-Star Algorithm

    PubMed Central

    Kusnanto, Hari; Herianto, Herianto

    2016-01-01

    Objectives Coronary heart disease is the leading cause of death worldwide, and it is important to diagnose the level of the disease. Intelligence systems for diagnosis proved can be used to support diagnosis of the disease. Unfortunately, most of the data available between the level/type of coronary heart disease is unbalanced. As a result system performance is low. Methods This paper proposes an intelligence systems for the diagnosis of the level of coronary heart disease taking into account the problem of data imbalance. The first stage of this research was preprocessing, which included resampled non-stratified random sampling (R), the synthetic minority over-sampling technique (SMOTE), clean data out of range attribute (COR), and remove duplicate (RD). The second step was the sharing of data for training and testing using a k-fold cross-validation model and training multiclass classification by the K-star algorithm. The third step was performance evaluation. The proposed system was evaluated using the performance parameters of sensitivity, specificity, positive prediction value (PPV), negative prediction value (NPV), area under the curve (AUC) and F-measure. Results The results showed that the proposed system provides an average performance with sensitivity of 80.1%, specificity of 95%, PPV of 80.1%, NPV of 95%, AUC of 87.5%, and F-measure of 80.1%. Performance of the system without consideration of data imbalance provide showed sensitivity of 53.1%, specificity of 88,3%, PPV of 53.1%, NPV of 88.3%, AUC of 70.7%, and F-measure of 53.1%. Conclusions Based on these results it can be concluded that the proposed system is able to deliver good performance in the category of classification. PMID:26893948

  18. Synthetic Diagnostic for the Evaluation of New Microwave Imaging Reflectometry System for Large Tokomaks - DIII-D and KSTAR

    NASA Astrophysics Data System (ADS)

    Lei, Li Juan

    Microwave Imaging Reflectometry (MIR) systems have been used as diagnostic tools for characterization of fluctuating plasma density in large tokamaks. Such a technique has been implemented on the TEXTOR device [H. Park, et al., Review of Scientific Instruments, 2004] and is being continued on DIII-D and KSTAR. To develop a new MIR system for density fluctuation measurements for DIII-D and KSTAR, one requires an understanding of how to preserve phase information. The current design for an MIR optical system makes use of design tools in free space, which is great for evaluation of port access but not provide significant information when it comes to the plasma region. This thesis describes a numerical study of MIR in the presence of turbulent fluctuations by evaluating the effectiveness in coupling the reflection layer in the full wave region and the detector array in free space with respect to fluctuation levels. A synthetic diagnostic tool making use of 2D full-wave diffractive simulation in full plasma geometry is applied to couple an optical imaging system with different optical arrangements.

  19. Edge electron density profiles and fluctuations measured by two-dimensional beam emission spectroscopy in the KSTAR

    SciTech Connect

    Nam, Y. U. Wi, H. M.; Zoletnik, S.; Lampert, M.; Kovácsik, Ákos

    2014-11-15

    Beam emission spectroscopy (BES) system in Korea Superconducting Tokamak Advanced Research (KSTAR) has recently been upgraded. The background intensity was reduced from 30% to 2% by suppressing the stray lights. This allows acquisition of the relative electron density profiles on the plasma edge without background subtraction from the beam power modulation signals. The KSTAR BES system has its spatial resolution of 1 cm, the temporal resolution of 2 MHz, and a total 32 channel (8 radial × 4 poloidal) avalanche photo diode array. Most measurements were done on the plasma edge, r/a ∼ 0.9, with 8 cm radial measurement width that covers the pedestal range. High speed density profile measurements reveal temporal behaviors of fast transient events, such as the precursors of edge localized modes and the transitions between confinement modes. Low background level also allows analysis of the edge density fluctuation patterns with reduced background fluctuations. Propagation of the density structures can be investigated by comparing the phase delays between the spatially distributed channels.

  20. Non-intrusive OSNR measurement of polarization-multiplexed signals with spectral shaping and subject to fiber non-linearity with minimum channel spacing of 37.5GHz.

    PubMed

    Gariépy, Daniel; Searcy, Steven; He, Gang; Tibuleac, Sorin

    2016-09-01

    A non-intrusive OSNR measurement technique relying on the detailed spectral comparison of an optical signal with its "noise-free" spectrum is described, including mathematical basis, validity conditions and algorithmic steps. The technique's performance is experimentally demonstrated with 100G PM-QPSK and 200G PM-16QAM signals subject to fiber non-linearity induced by 100G PM-QPSK and 10G NRZ-OOK neighbors. The OSNR measurement performance is also demonstrated when root-raised cosine spectral shaping is applied to the signals, with channel spacings of 50GHz and 37.5GHz. Experimental results for OSNR levels up to 30dB and launch powers up to 3dB above the optimum BER launch conditions are shown for different system and signal configurations. PMID:27607623

  1. Installation of soft X-ray array diagnostics and its application to tomography reconstruction using synthetic KSTAR X-ray images

    SciTech Connect

    Lee, Seung Hun; Jang, Juhyeok; Hong, Joohwan; Jang, Siwon; Choe, Wonho; Pacella, D.; Romano, A.; Gabellieri, L.; Kim, Junghee

    2014-11-15

    Four-array system of soft X-ray diagnostics was installed on KSTAR tokamak. Each array has 32 viewing chords of two photo-diode array detectors with spatial resolution of 2 cm. To estimate signals from the soft X-ray radiation power, typical n{sub e}, T{sub e}, and argon impurity line radiation profiles in KSTAR are chosen. The photo-diodes were absolutely calibrated as a function of the incident photon energy in 2–40 keV range with a portable X-ray tube. Two-dimensional T{sub e} image properties by multi-energy method were simulated and visualized with six combinations of beryllium filter sets within the dynamic range of signal ratio.

  2. Characteristics of toroidal rotation and ion temperature pedestals between ELM bursts in KSTAR H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Ko, S. H.; Kwon, J. M.; Ko, W. H.; Kim, S. S.; Jhang, H.; Terzolo, L.

    2016-06-01

    Steep pedestal profiles of ion temperature (Ti) and toroidal rotation ( V ϕ ) are routinely observed in neutral beam injection (NBI)-heated KSTAR H-mode plasmas [W. H. Ko et al., Nucl. Fusion 55, 083013 (2015)]. In this work, we report a result of detailed analysis of pedestal characteristics. By analyzing a set of data with different experimental conditions, we show that Ti and V ϕ pedestals are coupled to each other and correlation between them becomes stronger when NBI-torque is lower. This suggests the existence of intrinsic toroidal torque in the pedestal. Based on a 1D transport analysis, we find that the prevalence of residual micro-turbulences is necessary to explain momentum transport in the pedestal. The estimated strength of intrinsic torque is shown to be comparable to that from a 2.7 MW NBI source. Finally, we show that non-diffusive momentum flux is indispensable to explain momentum transport in the pedestal, and a residual stress model fits the observed momentum flux reasonably.

  3. Characteristics of Neoclassical Toroidal Viscosity in NSTX and KSTAR for Rotation Control and the Evaluation of Plasma Response

    NASA Astrophysics Data System (ADS)

    Sabbagh, S. A.; Berkery, J. W.; Park, Y. S.; Bell, R. E.; Gates, D. A.; Gerhardt, S. P.; Goumiri, I.; Evans, T. E.; Ferraro, N.; Jeon, Y. M.; Ko, W.; Shaing, K. C.; Sun, Y.

    2014-10-01

    Three-dimensional magnetic fields producing non-resonant magnetic braking allow control of the plasma rotation profile, ωφ, in tokamaks. Experimental angular momentum alteration created by 3D field configurations with dominant n = 2 and n = 3 components in NSTX is compared to theoretical neoclassical toroidal viscosity (NTV) torque density profiles, TNTV. Large radial variations of TNTV are typically found when flux surface displacements are computed using ideal MHD assumptions. In contrast, experimentally measured TNTV does not show strong torque localization. This may be explained by ion banana width orbit-averaging effects. A favorable characteristic for ωφ control clearly illustrated by KSTAR experiments is the lack of hysteresis of ωφ when altered by non-resonant NTV. Results from a model-based rotation controller designed using NBI and NTV from the applied 3D field as actuators are shown. The dependence of TNTV on δB2 significantly constrains the allowable field amplification in plasma response models when compared to experiment. Initial analysis shows that the single fluid model in the M3D-C1 resistive MHD code produces a flux surface-averaged δB consistent with the experimentally measured TNTV. Supported by US DOE Contracts DE-FG02-99ER54524 and DE-AC02-09CH11466.

  4. KSTAR stability and rotation control results for high normalized beta plasmas exceeding the ideal MHD no-wall stability limit

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Jeon, Y. M.; Lee, S. G.; Ko, W. H.; Hahn, S. H.; Bak, J. G.; You, K.-I.; Park, J. K.; Choi, M. J.; Yun, G. S.; Park, H. K.

    2013-10-01

    Plasma stability parameters in KSTAR have reached and exceeded the n = 1 ideal no-wall limit computed for H-mode profiles. Normalized beta up to 2.9 has been achieved and sustained with plasma internal inductance near 0.75. The ratio βN/li has exceeded 3.6 (an 80% increase over the prior year). Plasma stored energy has exceeded 0.5 MJ. Non-axisymmetric field spectra with dominant n = 2 component were applied to alter the plasma rotation profile by non-resonant neoclassical toroidal viscosity (NTV). The rotation profile was significantly altered without tearing activity or mode locking. Changing the in-vessel control coil current in steps altered rotation in a controlled fashion without hysteresis. The core rotation was lowered by 50% as measured by charge exchange spectroscopy, x-ray crystal spectrometer, and supported by magnetic diagnostics. H-mode energy confinement was maintained at reduced rotation while the resultant profile was peaked, as found in L-mode. Tearing mode onset conditions and mode locking criteria due to the applied n = 1, 2 applied fields were investigated. Additionally, ELMs were mitigated using sufficient n = 2 field strength by using midplane coils alone. Advances from the recent run campaign will be reported. Supported by U.S. DOE grant DE-FG02-99ER54524.

  5. Stability analysis of a C-band 500-kW klystron with a multi-cell output cavity

    NASA Astrophysics Data System (ADS)

    Hwang, Jihyun; Park, Sung-Ju; Namkung, Won; Cho, Moohyun

    2016-09-01

    A prototype 5-GHz 500-kW CW klystron (model E3762 provided by Toshiba Electron Tubes & Devices Co. Ltd.) has been operating as the RF source for the lower hybrid current drive (LHCD) system in the KSTAR tokamak. A cavity design study is being carried out with a simulation code based on the main klystron's operation parameters in order to investigate how the efficiency of the 5-GHz 500-kW CW klystron prototype can be enhanced. This is being done by simulating the klystron's performances for various cavity parameters, including the number of cavities, the inter-cavity distance, and the cavity's tuning frequencies. The simulation has been done with the FCI (field charge interaction) code aided by a matlab script for scanning input parameters. The initial set of scan parameters was obtained by benchmarking the E3762 klystron, and we are able to obtain optimized design parameters for a cavity system with better efficiency by adopting a multi-cell output cavity. However, the multi-cell output cavity is prone to self-oscillations due to the prolonged (several half RF periods) beam-field interaction along its multiple gaps. We have checked the feasibility of the optimization by evaluating the stability of the output cavity system. The stability is given by the ratio of a beam-loading conductance to the circuit conductance.

  6. Investigation of fast ion behavior using orbit following Monte-Carlo code in magnetic perturbed field in KSTAR

    NASA Astrophysics Data System (ADS)

    Shinohara, Kouji; Suzuki, Yasuhiro; Kim, Junghee; Kim, Jun Young; Jeon, Young Mu; Bierwage, Andreas; Rhee, Tongnyeol

    2016-11-01

    The fast ion dynamics and the associated heat load on the plasma facing components in the KSTAR tokamak were investigated with the orbit following Monte-Carlo (OFMC) code in several magnetic field configurations and realistic wall geometry. In particular, attention was paid to the effect of resonant magnetic perturbation (RMP) fields. Both the vacuum field approximation as well as the self-consistent field that includes the response of a stationary plasma were considered. In both cases, the magnetic perturbation (MP) is dominated by the toroidal mode number n  =  1, but otherwise its structure is strongly affected by the plasma response. The loss of fast ions increased significantly when the MP field was applied. Most loss particles hit the poloidal limiter structure around the outer mid-plane on the low field side, but the distribution of heat loads across the three limiters varied with the form of the MP. Short-timescale loss of supposedly well-confined co-passing fast ions was also observed. These losses started within a few poloidal transits after the fast ion was born deep inside the plasma on the high-field side of the magnetic axis. In the configuration studied, these losses are facilitated by the combination of two factors: (i) the large magnetic drift of fast ions across a wide range of magnetic surfaces due to a low plasma current, and (ii) resonant interactions between the fast ions and magnetic islands that were induced inside the plasma by the external RMP field. These effects are expected to play an important role in present-day tokamaks.

  7. High normalized beta plasmas exceeding the ideal stability limit and projected RWM active stabilization performance using newly installed feedback sensors in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Berkery, J. W.; Bialek, J. M.; Yoon, S. W.; Jeon, Y. M.; Bak, J. G.; Ko, W. H.; Hahn, S. H.; Bae, C.; Bae, Y. S.; in, Y. K.; Kim, J.; Lee, S. G.; Kwak, J. G.; Oh, Y. K.; Park, H. K.; Choi, M. J.; Yun, G. S.

    2015-11-01

    H-mode plasma operation of KSTAR has been expanded to significantly surpass the ideal MHD no-wall beta limit by achieving normalized beta up to 4.3 while reducing plasma internal inductance to near 0.7 exceeding the computed n = 1 ideal no-wall limit by a factor of 1.6. These high normalized beta values have been achieved in discharges having BT in the range 0.9-1.1 T after the plasma reached flattop current of 0.35-0.4 MA, with the highest neutral beam heating power of 4 MW. A significant conclusion of the analysis of these plasmas is that low- n global kink/ballooning or RWMs were not detected, and therefore were not the cause of the plasma termination. Advances from the 2015 run campaign aiming to achieve prolonged pulse duration at maximum normalized beta and to subsequently investigate the MHD stability of these plasmas will be reported. As KSTAR H-mode operation can now routinely surpass the ideal no-wall stability limit, n = 1 RWM active control is planned for the device. RWM active feedback using a newly installed set of poloidal magnetic field sensors mounted on the passive stabilizer plates and designed for optimal performance is analyzed using the VALEN-3D code. The advantages of the new sensors over other device sensors for RWM active control are discussed. Supported by U.S. DOE grant DE-FG02-99ER54524.

  8. Two-dimensional imaging of edge-localized modes in KSTAR plasmas unperturbed and perturbed by n=1 external magnetic fields

    SciTech Connect

    Yun, G. S.; Lee, W.; Choi, M. J.; Lee, J.; Park, H. K.; Domier, C. W.; Luhmann, N. C. Jr.; Tobias, B.; Donne, A. J. H.; Lee, J. H.; Jeon, Y. M.; Yoon, S. W.; Collaboration: KSTAR Team

    2012-05-15

    The temporal evolution of edge-localized modes (ELMs) has been studied using a 2-D electron cyclotron emission imaging system in the KSTAR tokamak. The ELMs are observed to evolve in three distinctive stages: the initial linear growth of multiple filamentary structures having a net poloidal rotation, the interim state of regularly spaced saturated filaments, and the final crash through a short transient phase characterized by abrupt changes in the relative amplitudes and distance among filaments. The crash phase, typically consisted of multiple bursts of a single filament, involves a complex dynamics, poloidal elongation of the bursting filament, development of a fingerlike bulge, and fast localized burst through the finger. Substantial alterations of the ELM dynamics, such as mode number, poloidal rotation, and crash time scale, have been observed under external magnetic perturbations with the toroidal mode number n= 1.

  9. Dynamics of multiple flux tubes in sawtoothing KSTAR plasmas heated by electron cyclotron waves: I. Experimental analysis of the tube structure

    NASA Astrophysics Data System (ADS)

    Choe, G. H.; Yun, G. S.; Nam, Y.; Lee, W.; Park, H. K.; Bierwage, A.; Domier, C. W.; Luhmann, N. C., Jr.; Jeong, J. H.; Bae, Y. S.; the KSTAR Team

    2015-01-01

    Multiple (two or more) flux tubes are commonly observed inside and/or near the q = 1 flux surface in KSTAR tokamak plasmas with localized electron cyclotron resonance heating and current drive (ECH/CD). Detailed 2D and quasi-3D images of the flux tubes obtained by an advanced imaging diagnostic system showed that the flux tubes are m/n = 1/1 field-aligned structures co-rotating around the magnetic axis. The flux tubes typically merge together and become like the internal kink mode of the usual sawtooth, which then collapses like a usual sawtooth crash. A systematic scan of ECH/CD beam position showed a strong correlation with the number of flux tubes. In the presence of multiple flux tubes close to the q = 1 surface, the radially outward heat transport was enhanced, which explains naturally temporal changes of electron temperature. We emphasize that the multiple flux tubes are a universal feature distinct from the internal kink instability and play a critical role in the control of sawteeth using ECH/CD.

  10. An initial measurement of a fast neutral spectrum for ion cyclotron range of frequency heated plasma using two-channel compact neutral particle analyzers in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Wang, S. J.; Park, M.; Kim, S. K.

    2013-11-01

    The accurate measurement of fast neutral particles from high energy ion tails is very important since it is a measure of ion cyclotron range of frequency (ICRF) or neutral beam (NB) ion heating. In KSTAR, fast neutral measurements have been carried out using a compact neutral particle analyzer based on the silicon photo diode since 2010. As a result, the fast neutral spectrum was observed consistent with the ion temperature, diamagnetic energy, and neutron flux in 2011. However, there was fast neutral count beyond the injected neutral beam energy in NB-only heating. Since it is difficult to expect the count unless the temperature is high enough to diffuse the fast ions beyond the beam energy it was required to identify what it is. During the 2012 campaign, the two-channel diode detectors with and without a particle stopper were used to distinguish fast neutral counts and other counts by a hard X-ray or neutrons. As a result, it was confirmed that the high energy component beyond the beam energy originated from a hard X-ray or neutrons. Finally, it was observed that faster neutrals are generated by ICRF heating and enhanced by electron cyclotron heating compared to NB-only heating.

  11. An initial measurement of a fast neutral spectrum for ion cyclotron range of frequency heated plasma using two-channel compact neutral particle analyzers in KSTAR

    SciTech Connect

    Kim, S. H.; Park, M.; Kim, S. K.; Wang, S. J.

    2013-11-15

    The accurate measurement of fast neutral particles from high energy ion tails is very important since it is a measure of ion cyclotron range of frequency (ICRF) or neutral beam (NB) ion heating. In KSTAR, fast neutral measurements have been carried out using a compact neutral particle analyzer based on the silicon photo diode since 2010. As a result, the fast neutral spectrum was observed consistent with the ion temperature, diamagnetic energy, and neutron flux in 2011. However, there was fast neutral count beyond the injected neutral beam energy in NB-only heating. Since it is difficult to expect the count unless the temperature is high enough to diffuse the fast ions beyond the beam energy it was required to identify what it is. During the 2012 campaign, the two-channel diode detectors with and without a particle stopper were used to distinguish fast neutral counts and other counts by a hard X-ray or neutrons. As a result, it was confirmed that the high energy component beyond the beam energy originated from a hard X-ray or neutrons. Finally, it was observed that faster neutrals are generated by ICRF heating and enhanced by electron cyclotron heating compared to NB-only heating.

  12. Non-inductive initiation of closed flux surfaces by ECH/ECCD on KSTAR using an oblique fundamental O-mode injection from the low-field side

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Uchida, M.; Maekawa, T.; Bae, Y.-S.; Joung, M.; Jeong, J. H.; KSTAR Team

    2016-04-01

    An experiment on non-inductive plasma current start-up by electron cyclotron (EC) heating and current drive (ECH/ECCD) has been carried out on KSTAR by injecting the fundamental O-mode wave from the low-field side obliquely to the toroidal magnetic field. A plasma current up to 14.5 kA is generated by 180 kW of 84 GHz microwave power and the magnetic measurement shows the formation of a large last-closed flux surface with a diameter of 0.4 m. The soft x-ray emission profile and fast CCD images also support the existence of closed flux surfaces. The current of the cross-field-passing electrons (CFPEs) is calculated according to the paper Nucl. Fusion 52 083008 in these experimental conditions, and it is shown that a CFPE current can produce the initial closed flux surfaces. The observed large increase of EC emission supports the generation of energetic electrons, like CFPEs. After the formation of the closed flux surfaces, the pressure-driven current and CFPE current do not flow in the closed flux surfaces. EC-driven current should flow in these surfaces and ramp up the plasma current. It is estimated that an EC-driven current of about one third of the total plasma current flows in the closed flux surface at the last stage.

  13. A time-dependent angular analysis of B0s to J/psi phi and B0d to J/psi Kstar0, and, A measurement of the width difference in the B0s system

    NASA Astrophysics Data System (ADS)

    Li, Ke

    The mixing between Bs0 - Bs0 bar and Bd0 - Bd0 bar leads to the two eigenstates of definite masses (heavy, m H and light, m L) and widths (GammaH and GammaL). The mass differences in the two systems have an important impact on our knowledge of the unitary triangle and the Standard Model. The mass difference Delta md has been well measured. However no direct measurements of Delta m s have been made because of the high oscillation frequency in B0s system. A large mass difference suggests a large and measurable width difference (Delta m s ≡ Gamma L - Gamma H, which can be used (and may be the only achievable way currently) to determine Delta m s. The B0s to J/psi phi and B0d to J/psi Kstar0 are pseudo-sealer to vector-vector decays governed by three decay amplitudes, representing the coupling of the B meson to states polarized longitudinally A0, and parallel A parallel or perpendicularly A perp in the transverse plane. In the B0s system, the mass eigenstates are nearly CP eigenstates and so are the final observed polarized states. A combined analysis based on lifetime and angular information allows for a separation of the heavy (CP odd) and light (CP even) eigenstates and a measurement of the width difference. The channel B0d to J/psi Kstar0 is related to B0s to J/psi phi by SU(3) flavor symmetry, and provides a powerful validation of the analysis technique. In this dissertation, I present a time-dependent analysis of these decays based on the dimuon data collected by the CDF Collaboration at Fermi National Accelerator Laboratory from February 2002 to February 2004 during the Run II of the Tevatron, corresponding to a total luminosity of approximately 260 inv pb. From these data, I measure the transverse amplitudes of the two decays, the lifetimes of the B0s (heavy and light) and the B0d and the width difference in the B0s system. For B0s, we obtain: A0=0.784+/-0.039+/-0.007 Aparallel=0.510+/-0.08 2+/-0.013e1.94+/- 0.36+/-0.03i Aperp=0. 354+/-0.098+/-0.003 tauL=1

  14. The 1.0-4.5 GHz Zebras in the June 6, 2000 Flare

    NASA Astrophysics Data System (ADS)

    Sawant, H. S.; Karlický, M.; Fernandes, F. C. R.; Cecatto, J. R.

    2002-01-01

    For the first time we are reporting harmonically related zebra structures above 1000 MHz, having ratio of 1:2. Zebra structures show up to 8 zebra lines. In individual zebra patterns the frequency ratio of the neighbouring zebra lines are less than 1.03 and these ratios decrease with the frequency decrease. The zebra patterns are analyzed and interpreted assuming double plasma resonance instability as the cause for their generation. The longitudinal upper hybrid waves are excited at positions of cyclotron resonances and then transformed into electromagnetic ones. Using this model the magnetic field strengths in the flaring loops are estimated in the range of 110-230 G.

  15. Low power considerations and design for CMOS VCOs applied for direct conversion receivers at 5GHz

    NASA Astrophysics Data System (ADS)

    Adin, Iñigo; Quemada, Carlos; Solar, Hector; Sedano, Beatriz; Gutierrez, Iñigo

    2007-05-01

    Low power design often requires direct conversion architectures, such as low-IF or zero-IF. Any of these two possibilities needs a low power, low phase noise voltage control oscillator (VCO) in the frequency synthesizer. This work is focused on low power considerations applied to the practical modern conception of this device. Fulfilling the standard specifications (output power, phase noise, frequency range) should be completed with this deeper step. A conscious design leads moreover to an improvement in the results obtained by the classical considerations. The increase of the quality factor of the passive elements is one of the key points, followed by an accurate design of the architecture scheme. Furthermore, lower current consumption provides higher oscillation frequencies and facilitates higher frequency ranges, which follow the trends of modern wireless and wideband communication standards. In order to validate the aforementioned assumptions, a CMOS VCO has been implemented in UMC 0.18μm 1P6M technology, with power consumption down to 3.4mW.

  16. Long-term 1. 5 GHz amplitude scintillation measurements at the magnetic equator

    SciTech Connect

    Basu, S.; Basu, S.; Mullen, J.P.; Bushby, A.

    1980-04-01

    The diurnal and seasonal behavior of long-term (approximately 20 months) 1.54 GHz amplitude scintillation measurements under low sunspot conditions observed at Huancayo, Peru are presented. The measurements refer to a low elevation geometry in the E-W plane at the magnetic equator. The data show clear equinoctal maxima of occurrence and confinement to the pre-midnight hours. There is a total absence of scintillations during the May--July period.

  17. Development of a 39.5 GHz Karp traveling wave tube for use in space

    NASA Technical Reports Server (NTRS)

    Jacquez, A.; Wilson, D.

    1988-01-01

    A millimeter-wave TWT was developed using a dispersive, high-impedance forward wave interaction structure based on a ladder, with non-space-harmonic interaction, for a tube with high gain per inch and high efficiency. The 'Tunneladder' interaction structure combines ladder properties modified to accommodate Pierce gun beam optics on a radially magnetized PM focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to each ridge of a double ridged waveguide. Cold-test data are presented, representing the omega-Beta and impedance characteristics of the modified ladder circuit These results were used in small and large-signal computer programs to predict TWT gain and efficiency. A laboratory model tube was designed and fabricated, including all major subassemblies.

  18. Development of a 39.5 GHz Karp traveling wave tube for use in space

    NASA Astrophysics Data System (ADS)

    Jacquez, A.; Wilson, D.

    1988-10-01

    A millimeter-wave TWT was developed using a dispersive, high-impedance forward wave interaction structure based on a ladder, with non-space-harmonic interaction, for a tube with high gain per inch and high efficiency. The 'Tunneladder' interaction structure combines ladder properties modified to accommodate Pierce gun beam optics on a radially magnetized PM focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to each ridge of a double ridged waveguide. Cold-test data are presented, representing the omega-Beta and impedance characteristics of the modified ladder circuit These results were used in small and large-signal computer programs to predict TWT gain and efficiency. A laboratory model tube was designed and fabricated, including all major subassemblies.

  19. 78 FR 37499 - Unlicensed National Information Infrastructure (U-NII) Devices in the 5 GHz Band

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-21

    ..., 2013, and released June 17, 2013. The full text of this document is available for inspection and... reply comment deadline to facilitate the development of a full and complete record. DATES: Reply...., Washington, DC 20554. The complete text of this document also may be purchased from the Commission's...

  20. A Compact 5.5 GHz Band-Rejected UWB Antenna Using Complementary Split Ring Resonators

    PubMed Central

    Islam, M. M.; Faruque, M. R. I.; Islam, M. T.

    2014-01-01

    A band-removal property employing microwave frequencies using complementary split ring resonators (CSRRs) is applied to design a compact UWB antenna wishing for the rejection of some frequency band, which is meanwhile exercised by the existing wireless applications. The reported antenna comprises optimization of a circular radiating patch, in which slotted complementary SRRs are implanted. It is printed on low dielectric FR4 substrate material fed by a partial ground plane and a microstrip line. Validated results exhibit that the reported antenna shows a wide bandwidth covering from 3.45 to more than 12 GHz, with a compact dimension of 22 × 26 mm2, and VSWR < 2, observing band elimination of 5.5 GHz WLAN band. PMID:24971379

  1. A fully integrated 3.5 GHz CMOS differential power amplifier driver

    NASA Astrophysics Data System (ADS)

    Xiaodong, Xu; Haigang, Yang; Tongqiang, Gao; Hongfeng, Zhang

    2013-07-01

    A fully integrated CMOS differential power amplifier driver (PAD) is proposed for WiMAX applications. In order to fulfill the differential application requirements, a transmission line transformer is used as the output matching network. A differential inductance constitutes an inter-stage matching network. Meanwhile, an on chip balun realizes input matching as well as single-end to differential conversion. The PAD is fabricated in a 0.13 μm RFCMOS process. The chip size is 1.1 × 1.1 mm2 with all of the matching network integrated on chip. The saturated power is around 10 dBm and power gain is about 12 dB.

  2. 78 FR 21320 - Unlicensed National Information Infrastructure (U-NII) Devices in the 5 GHz Band

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-10

    ...). See Electronic Filing of Documents in Rulemaking Proceedings, 63 FR 24121 (1998). Electronic Filers... $100 billion through avoidance of unnecessary costs. 11. In addition, Congress has enacted legislation...; (c) the device does not include configuration controls to change the frequency of operation to...

  3. Attenuation of soil microwave emissivity by corn and soybeans at 1.4 and 5 GHz

    NASA Technical Reports Server (NTRS)

    Jackson, Thomas J.; O'Neill, Peggy E.

    1989-01-01

    Theory and experiments have shown that passive microwave radiometers can be used to measure soil moisture. However, the presence of a vegetative cover alters the measurement that might be obtained under bare conditions. Deterministically accounting for the effect of vegetation and developing algorithms for extracting soil moisture from observations of a vegetable-soil complex present significant obstacles to the practical use of this approach. The presence of a vegetation canopy reduces the sensitivity of passive microwave instruments to soil moisture variations. The reduction in sensitivity, as compared to a bare-soil relationship, increases as microwave frequency increases, implying that the longest wavelength sensors should provide the most information. Sensitivity also decreases as the amount of vegetative wet biomass increases for a given type of vegetation.

  4. New space research frequency band proposals in the 20- to 40.5-GHz range

    NASA Technical Reports Server (NTRS)

    Bishop, D. F.

    1991-01-01

    Future space research communications systems may require spectra above 20 GHz. Frequency bands above 20 GHz are identified that are suitable for space research. The selection of the proper bands depends on consideration of interference with other radio services, adequate bandwidths, link performance, and technical requirements for practical implementation.

  5. The design and performance of a 2.5-GHz telecommand link for wireless biomedical monitoring.

    PubMed

    Crumley, G C; Evans, N E; Scanlon, W G; Burns, J B; Trouton, T G

    2000-12-01

    This paper details the implementation and operational performance of a minimum-power 2.45-GHz pulse receiver and a companion on-off keyed transmitter for use in a semi-active, duplex RF biomedical transponder. A 50-ohm microstrip stub-matched zero-bias diode detector forms the heart of a body-worn receiver that has a (CMOS baseband amplifier consuming 20 microA from +3 V and achieves a tangential sensitivity of -53 dBm. The base transmitter generates 0.5 W of peak RF output power into 50 ohms. Both linear and right-hand circularly polarized Tx-Rx antenna sets were employed in system reliability trials carried out in a hospital Coronary Care Unit. For transmitting antenna heights between 0.3 and 2.2 m above floor level, transponder interrogations were 95% reliable within the 67-m2 area of the ward, falling to an average of 46% in the surrounding rooms and corridors. Overall, the circular antenna set gave the higher reliability and lower propagation power decay index. PMID:11206813

  6. The Second Arecibo Search for 5 GHz Radio Flares from Ultracool Dwarfs

    NASA Astrophysics Data System (ADS)

    Route, Matthew; Wolszczan, Alexander

    2016-10-01

    We describe our second installment of the 4.75 GHz survey of ultracool dwarfs (UCDs) conducted with the Arecibo radio telescope, which has observed 27 such objects and resulted in the detection of sporadic flaring from the T6 dwarf, WISEPC J112254.73+255021.5. We also present follow-up observations of the first radio-emitting T dwarf, 2MASS J10475385+2124234, a tentatively identified radio-emitting L1 dwarf, 2MASS J1439284+192915, and the known radio-flaring source, 2MASS J13142039+132011 AB. Our new data indicate that 2MASS J1439284+192915 is not a radio-flaring source. The overall detection rate of our unbiased survey for radio-flaring UCDs is ∼5% for new sources, with a detection rate for each spectral class of ∼5%–10%. Evidently, radio luminosity of the UCDs does not appear to monotonically decline with spectral type from M7 dwarfs to giant planets, contradictory to theories of the magnetic field generation and the internal structure of these objects. Along with other, recently published results, our data exemplify the unique value of using radio surveys to reveal and study properties of substellar magnetic activity.

  7. THE 5 GHz ARECIBO SEARCH FOR RADIO FLARES FROM ULTRACOOL DWARFS

    SciTech Connect

    Route, Matthew; Wolszczan, Alexander E-mail: alex@astro.psu.edu

    2013-08-10

    We present the results of a 4.75 GHz survey of 33 brown dwarfs and one young exoplanetary system for flaring radio emission, conducted with the 305 m Arecibo radio telescope. The goal of this program was to detect and characterize the magnetic fields of objects cooler than spectral type L3.5, the coolest brown dwarf detected prior to our survey. We have also attempted to detect flaring radio emission from the HR 8799 planetary system, guided by theoretical work indicating that hot, massive exoplanets may have strong magnetic fields capable of generating radio emission at GHz frequencies. We have detected and confirmed radio flares from the T6.5 dwarf 2MASS J10475385+2124234. This detection dramatically extends the temperature range over which brown dwarfs appear to be at least sporadic radio-emitters, from 1900 K (L3.5) down to 900 K (T6.5). It also demonstrates that the utility of radio detection as a unique tool to study the magnetic fields of substellar objects extends to the coolest dwarfs, and, plausibly to hot, massive exoplanets. We have also identified a single, 3.6{sigma} flare from the L1 dwarf, 2MASS J1439284+192915. This detection is tentative and requires confirmation by additional monitoring observations.

  8. Design of a 1-MW CW 8.5 GHz transmitter for planetary RADAR

    NASA Technical Reports Server (NTRS)

    Hoppe, Daniel J.; Bhanji, Alaudin M.

    1990-01-01

    A proposed conceptual design for increasing the output power of an existing X-band planetary radar transmitter from 365 kW to 1 MW CW is discussed. The paper covers the basic transmitter system requirements as dictated by the specifications for the radar. The characteristics and expected performance of the high-power klystrons are considered and the transmitter power amplifier system is discussed. Also included in the discussion is the design of the exiter system. Two alternative feed systems for delivering the 1-MW CW signal to the antenna system are described. The expected performance of the beam supply, heat exchanger, and monitor and control devices is also presented. Finally, an assessment of the state-of-the-art technology to meet system requirements is given and possible areas of difficulty are summarized.

  9. The design and performance of a 2.5-GHz telecommand link for wireless biomedical monitoring.

    PubMed

    Crumley, G C; Evans, N E; Scanlon, W G; Burns, J B; Trouton, T G

    2000-12-01

    This paper details the implementation and operational performance of a minimum-power 2.45-GHz pulse receiver and a companion on-off keyed transmitter for use in a semi-active, duplex RF biomedical transponder. A 50-ohm microstrip stub-matched zero-bias diode detector forms the heart of a body-worn receiver that has a (CMOS baseband amplifier consuming 20 microA from +3 V and achieves a tangential sensitivity of -53 dBm. The base transmitter generates 0.5 W of peak RF output power into 50 ohms. Both linear and right-hand circularly polarized Tx-Rx antenna sets were employed in system reliability trials carried out in a hospital Coronary Care Unit. For transmitting antenna heights between 0.3 and 2.2 m above floor level, transponder interrogations were 95% reliable within the 67-m2 area of the ward, falling to an average of 46% in the surrounding rooms and corridors. Overall, the circular antenna set gave the higher reliability and lower propagation power decay index.

  10. A lower hybrid current drive system for ITER

    NASA Astrophysics Data System (ADS)

    Hoang, G. T.; Bécoulet, A.; Jacquinot, J.; Artaud, J. F.; Bae, Y. S.; Beaumont, B.; Belo, J. H.; Berger-By, G.; Bizarro, João P. S.; Bonoli, P.; Cho, M. H.; Decker, J.; Delpech, L.; Ekedahl, A.; Garcia, J.; Giruzzi, G.; Goniche, M.; Gormezano, C.; Guilhem, D.; Hillairet, J.; Imbeaux, F.; Kazarian, F.; Kessel, C.; Kim, S. H.; Kwak, J. G.; Jeong, J. H.; Lister, J. B.; Litaudon, X.; Magne, R.; Milora, S.; Mirizzi, F.; Namkung, W.; Noterdaeme, J. M.; Park, S. I.; Parker, R.; Peysson, Y.; Rasmussen, D.; Sharma, P. K.; Schneider, M.; Synakowski, E.; Tanga, A.; Tuccillo, A.; Wan, Y. X.

    2009-07-01

    A 20 MW/5 GHz lower hybrid current drive (LHCD) system was initially due to be commissioned and used for the second mission of ITER, i.e. the Q = 5 steady state target. Though not part of the currently planned procurement phase, it is now under consideration for an earlier delivery. In this paper, both physics and technology conceptual designs are reviewed. Furthermore, an appropriate work plan is also developed. This work plan for design, R&D, procurement and installation of a 20 MW LHCD system on ITER follows the ITER Scientific and Technical Advisory Committee (STAC) T13-05 task instructions. It gives more details on the various scientific and technical implications of the system, without presuming on any work or procurement sharing amongst the possible ITER partnersb The LHCD system of ITER is not part of the initial cost sharing.. This document does not commit the Institutions or Domestic Agencies of the various authors in that respect.

  11. RF Surface Impedance Measurement of Polycrystalline and Large Grain Nb Disk Sample at 7.5 GHz

    SciTech Connect

    Xiao, Binping; Geng, Rongli; Kelley, Michael J.; Marhauser, Frank; Phillips, H. Larry; Reece, Charles E.; Wang, Haipeng

    2009-11-01

    A Surface Impedance Characterization (SIC) system has been proposed at the 2005 SRF workshop and recently updated as detailed at the 2009 PAC conference. Currently the SIC system can measure samples in a temperature range from 2K to 20K exposed to an RF magnetic flux density of less than 3mT. We report on new results of a BCP etched large grain Nb sample measured with this system as compared with previous results of a BCP etched polycrystalline Nb sample. The design of an upgraded SIC system for use at higher magnetic flux densities is on the way to more efficiently investigate correlations between local material characteristics and associated SRF properties, both for preparation studies of bulk niobium and also new thin film SRF developments.

  12. Efficient generation of twin photons at telecom wavelengths with 2.5 GHz repetition-rate-tunable comb laser.

    PubMed

    Jin, Rui-Bo; Shimizu, Ryosuke; Morohashi, Isao; Wakui, Kentaro; Takeoka, Masahiro; Izumi, Shuro; Sakamoto, Takahide; Fujiwara, Mikio; Yamashita, Taro; Miki, Shigehito; Terai, Hirotaka; Wang, Zhen; Sasaki, Masahide

    2014-01-01

    Efficient generation and detection of indistinguishable twin photons are at the core of quantum information and communications technology (Q-ICT). These photons are conventionally generated by spontaneous parametric down conversion (SPDC), which is a probabilistic process, and hence occurs at a limited rate, which restricts wider applications of Q-ICT. To increase the rate, one had to excite SPDC by higher pump power, while it inevitably produced more unwanted multi-photon components, harmfully degrading quantum interference visibility. Here we solve this problem by using recently developed 10 GHz repetition-rate-tunable comb laser, combined with a group-velocity-matched nonlinear crystal, and superconducting nanowire single photon detectors. They operate at telecom wavelengths more efficiently with less noises than conventional schemes, those typically operate at visible and near infrared wavelengths generated by a 76 MHz Ti Sapphire laser and detected by Si detectors. We could show high interference visibilities, which are free from the pump-power induced degradation. Our laser, nonlinear crystal, and detectors constitute a powerful tool box, which will pave a way to implementing quantum photonics circuits with variety of good and low-cost telecom components, and will eventually realize scalable Q-ICT in optical infra-structures. PMID:25524646

  13. 1.5-GHz voltage controlled oscillator with 3% tuning bandwidth using a two-pole DSBAR filter.

    PubMed

    Avramov, Ivan; Gilbert, Stephen R; Ruby, Rich

    2011-05-01

    First results on a novel voltage controlled oscillator (VCO) in the lower gigahertz range, featuring excellent phase noise and high power efficiency are presented. The heart of the VCO is a recently reported novel miniature two-pole decoupled stacked bulk acoustic resonator (DSBAR) filter. With its single 180° phase transition over the 1 dB bandwidth, linear phase, and maximum 1 dB insertion loss, it provides stable single-mode operation over 45 MHz (≈3%) of tuning bandwidth and has negligible heat dissipation when operated at incident power levels of 100 mW or greater. The 1.55-GHz laboratory VCO prototypes operate at 5 V supply voltage, 50 mA supply current, 15 dBm of output power, and >13% efficiency, demonstrating -84 and < -180 dBc/Hz phase noise suppression at 1 kHz carrier offset and in the thermal noise region, respectively. VCOs with cascaded DSBAR filters for further phase noise reduction are also demonstrated. PMID:21622047

  14. A Multi-Feed Receiver in the 18 to 26.5 GHz Band for Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Orfei, A.; Carbonaro, L.; Cattani, A.; Cremonini, A.; Cresci, L.; Fiocchi, F.; Maccaferri, A.; Maccaferri, G.; Mariotti, S.; Monari, J.; Morsiani, M.; Natale, V.; Nesti, R.; Panella, D.; Poloni, M.; Roda, J.; Scalambra, A.; Tofani, G.

    2010-08-01

    A large-bandwidth, state-of-the-art multi-feed receiver has been constructed to be used on the new 64 m Sardinia Radio Telescope (SRT) (http://www.srt.inaf.itl), an antenna aiming to work from 300 MHz to 100 GHz with an almost continuous frequency coverage. The goal of this new receiver is to speed up the survey of the sky with high sensitivity in a frequency band that is very interesting to radio astronomers. In the meantime, the antenna erection has been finalized, and the receiver has been mounted on the Medicina 32 m antenna to be tested (http://www.med.ira.inaf.itl). We present a complete description of the system, including a dedicated backend, and the results of the tests.

  15. Demonstration of particle exhaust control during ELM suppression by resonant magnetic perturbations in DIII-D

    SciTech Connect

    Hoang, G T; Becoulet, A.; Jacquinot, J; Milora, Stanley L; Rasmussen, David A

    2009-01-01

    A 20 MW/5 GHz lower hybrid current drive (LHCD) system was initially due to be commissioned and used for the second mission of ITER, i.e. the Q = 5 steady state target. Though not part of the currently planned procurement phase, it is now under consideration for an earlier delivery. In this paper, both physics and technology conceptual designs are reviewed. Furthermore, an appropriate work plan is also developed. This work plan for design, R&D, procurement and installation of a 20 MW LHCD system on ITER follows the ITER Scientific and Technical Advisory Committee (STAC) T13-05 task instructions. It gives more details on the various scientific and technical implications of the system, without presuming on any work or procurement sharing amongst the possible ITER partners(b). This document does not commit the Institutions or Domestic Agencies of the various authors in that respect.

  16. Effects of the q profile on toroidal rotation in Alcator C-Mod LHCD plasmas

    DOE PAGESBeta

    Rice, J. E.; Gao, C.; Mumgaard, R.; Parker, R. R.; Scott, S. D.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Delgado-Aparicio, L.; Fenzi, C.; et al

    2016-02-09

    Changes in the core toroidal rotation profiles following injection of lower hybrid (LH) waves have been documented in Alcator C-Mod plasmas. Shot by shot scans of LH input power have been performed at fixed magnetic field and electron density for several plasma currents. For sawtoothing target plasmas, if the input power is low enough that the central safety factor q0 remains below 1, the change in the core rotation is in the counter-current direction, consistent in sign, magnitude and LH power scaling with direct momentum input from the LH waves. If the power level is high enough that there aremore » significant changes to the q profile, including the termination of sawtooth oscillations, the change in the toroidal rotation is in the co-current direction, consistent with changes in the momentum flux through its dependence on the current density profile. Furthermore, the direction of the rotation changes depends on whether q0 is below or above unity, and seemingly not on the magnetic shear, nor the Ohmic confinement regime of the target plasma.« less

  17. Fast electron current density profile and diffusion studies during LHCD in PBX-M

    SciTech Connect

    Jones, S.E.; Kesner, J.; Luckhardt, S.; Paoletti, F.; von Goeler, S.; Bernabei, S.; Kaita, R.; Rimini, F.

    1993-08-01

    Successful current profile control experiments using lower hybrid current drive (LCHD) clearly require knowledge of (1) the location of the driven fast electrons and (2) the ability to maintain that location from spreading due to radial diffusion. These issues can be addressed by examining the data from the hard x-ray camera on PBX-M, a unique diagnostic producing two-dimensional, time resolved tangential images of fast electron bremsstrahlung. Using modeling, these line-of-sight images are inverted to extract a radial fast electron current density profile. We note that ``hollow`` profiles have been observed, indicative of off-axis current drive. These profiles can then be used to calculate an upper bound for an effective fast electron diffusion constant: assuming an extremely radially narrow lower hybrid absorption profile and a transport model based on Rax and Moreau, a model fast electron current density profile is calculated and compared to the experimentally derived profile. The model diffusion constant is adjusted until a good match is found. Applied to steady-state quiescent modes on PBX-M, we obtain an upper limit for an effective diffusion constant of about D*=1.1 m{sup 2}/sec.

  18. Effects of the q profile on toroidal rotation in Alcator C-Mod LHCD plasmas

    SciTech Connect

    Rice, J. E.; Mumgaard, R.; Parker, R.; Scott, S.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Delgado-Aparicio, L.; Fenzi, C.; Granetz, R. S.; Greenwald, M. J.; Hubbard, A. E.; Hughes, J. W.; Irby, J.; Lee, J. P.; Marmar, E. S.; Wolfe, S. M.

    2016-01-01

    Changes in the core toroidal rotation profiles following injection of lower hybrid (LH) waves have been documented in Alcator C-Mod plasmas. Shot by shot scans of LH input power have been performed at fixed magnetic field and electron density for several plasma currents. For sawtoothing target plasmas, if the input power is low enough that the central safety factor q0 remains below 1, the change in the core rotation is in the counter-current direction, consistent in sign, magnitude and LH power scaling with direct momentum input from the LH waves. If the power level is high enough that there are significant changes to the q profile, including the termination of sawtooth oscillations, the change in the toroidal rotation is in the co-current direction, consistent with changes in the momentum flux through its dependence on the current density profile. The direction of the rotation changes depends on whether q0 is below or above unity, and seemingly not on the magnetic shear, nor the Ohmic confinement regime of the target plasma.

  19. Ion gyroscale fluctuation measurement with microwave imaging reflectometer on KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, W.; Leem, J.; Yun, G. S.; Park, H. K.; Ko, S. H.; Wang, W. X.; Budny, R. V.; Luhmann, N. C.; Kim, K. W.

    2016-11-01

    Ion gyroscale turbulent fluctuations with the poloidal wavenumber kθ ˜ 3 cm-1 have been measured in the core region of the neutral beam (NB) injected low confinement (L-mode) plasmas on Korea superconducting tokamak advanced research. The turbulence poloidal wavenumbers are deduced from the frequencies and poloidal rotation velocities in the laboratory frame, measured by the multichannel microwave imaging reflectometer. Linear and nonlinear gyrokinetic simulations also predict the unstable modes with the normalized wavenumber kθρs ˜ 0.4, consistent with the measurement. Comparison of the measured frequencies with the intrinsic mode frequencies from the linear simulations indicates that the measured ones are primarily due to the E × B flow velocity in the NB-injected fast rotating plasmas.

  20. Computational modeling of temperature elevation and thermoregulatory response in the brains of anesthetized rats locally exposed at 1.5 GHz

    NASA Astrophysics Data System (ADS)

    Hirata, Akimasa; Masuda, Hiroshi; Kanai, Yuya; Asai, Ryuichi; Fujiwara, Osamu; Arima, Takuji; Kawai, Hiroki; Watanabe, Soichi; Lagroye, Isabelle; Veyret, Bernard

    2011-12-01

    The dominant effect of human exposures to microwaves is caused by temperature elevation ('thermal effect'). In the safety guidelines/standards, the specific absorption rate averaged over a specific volume is used as a metric for human protection from localized exposure. Further investigation on the use of this metric is required, especially in terms of thermophysiology. The World Health Organization (2006 RF research agenda) has given high priority to research into the extent and consequences of microwave-induced temperature elevation in children. In this study, an electromagnetic-thermal computational code was developed to model electromagnetic power absorption and resulting temperature elevation leading to changes in active blood flow in response to localized 1.457 GHz exposure in rat heads. Both juvenile (4 week old) and young adult (8 week old) rats were considered. The computational code was validated against measurements for 4 and 8 week old rats. Our computational results suggest that the blood flow rate depends on both brain and core temperature elevations. No significant difference was observed between thermophysiological responses in 4 and 8 week old rats under these exposure conditions. The computational model developed herein is thus applicable to set exposure conditions for rats in laboratory investigations, as well as in planning treatment protocols in the thermal therapy.

  1. The effect of ICRF and LHCD waveguide and launcher location on tritium breeding ratio and radiation damage

    NASA Astrophysics Data System (ADS)

    Sierchio, J. M.; Whyte, D. G.; Wallace, G. M.; Wukitch, S. J.

    2015-11-01

    In most tokamak fusion reactor designs, ion cyclotron radio frequency (ICRF) and lower hybrid (LH) waves used to heat the plasma and drive current are launched from the low magnetic field side where there is more access space. It has been recently proposed to launch these waves from the high-field side, which increases efficiency, allows for better wave penetration, and has favorable scrape-off-layer characteristics [Wallace RFPPC (2015)]. We investigate whether there are added benefits to high-field side launch compared with low-field side launch, including a smaller reduction in the tritium breeding ratio (TBR) and less radiation damage as measured by displacements per atom (DPA) and He retention. We present results obtained with MCNP for TBR, DPA, and He retention for several geometries including two liquid immersion blanket designs and two solid blanket designs, while varying the location of a generic waveguide and antenna. Supported by USDoE award DE-FC02-99ER54512.

  2. RF wave propagation and scattering in turbulent tokamak plasmas

    SciTech Connect

    Horton, W. Michoski, C.; Peysson, Y.; Decker, J.

    2015-12-10

    Drift wave turbulence driven by the steep electron and ion temperature gradients in H-mode divertor tokamaks produce scattering of the RF waves used for heating and current drive. The X-ray emission spectra produced by the fast electrons require the turbulence broaden RF wave spectrum. Both the 5 GHz Lower Hybrid waves and the 170 GHz electron cyclotron [EC] RF waves experience scattering and diffraction by the electron density fluctuations. With strong LHCD there are bifurcations in the coupled turbulent transport dynamics giving improved steady-state confinement states. The stochastic scattering of the RF rays makes the prediction of the distribution of the rays and the associated particle heating a statistical problem. Thus, we introduce a Fokker-Planck equation for the probably density of the RF rays. The general frame work of the coupled system of coupled high frequency current driving rays with the low-frequency turbulent transport determines the profiles of the plasma density and temperatures.

  3. RF wave propagation and scattering in turbulent tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Horton, W.; Michoski, C.; Peysson, Y.; Decker, J.

    2015-12-01

    Drift wave turbulence driven by the steep electron and ion temperature gradients in H-mode divertor tokamaks produce scattering of the RF waves used for heating and current drive. The X-ray emission spectra produced by the fast electrons require the turbulence broaden RF wave spectrum. Both the 5 GHz Lower Hybrid waves and the 170 GHz electron cyclotron [EC] RF waves experience scattering and diffraction by the electron density fluctuations. With strong LHCD there are bifurcations in the coupled turbulent transport dynamics giving improved steady-state confinement states. The stochastic scattering of the RF rays makes the prediction of the distribution of the rays and the associated particle heating a statistical problem. Thus, we introduce a Fokker-Planck equation for the probably density of the RF rays. The general frame work of the coupled system of coupled high frequency current driving rays with the low-frequency turbulent transport determines the profiles of the plasma density and temperatures.

  4. Taming Magnetically Confined Plasmas with RF Waves: A Historical Perspective

    NASA Astrophysics Data System (ADS)

    Porkolab, Miklos

    2009-11-01

    Heating and profile control by RF waves in magnetic fusion experiments has led to the development of a new area of physics, namely wave propagation and absorption in high temperature plasmas in complex magnetic field geometries. In addition, the development of high power microwave sources as well as novel antenna structures capable of handling high RF powers has also been necessary. In this talk I shall summarize the historical progression of relevant results in three frequency regimes, namely the ion cyclotron range of frequencies (ICRF), the electron cyclotron frequency and its harmonics (ECRH), and the lower hybrid frequency range (LHRF). In the ICRF regime breakthrough heating results were obtained in the 1980s in tokamaks with good confinement of energetic ions, such as PLT, TFTR and JET. In the period of late 1970s to mid 1980s the theory of RF current drive (LHCD, ECCD and that of fast wave, or FWCD) was developed. Soon thereafter efficient lower hybrid current drive was demonstrated in tokamak experiments such as Versator II, Alcator--C and PLT, and later JT60-U, Tore-Supra and JET. High harmonic FWCD has been also demonstrated on DIII-D and NSTX. Long pulse multi-MW LHCD experiments are now in preparation on the new superconducting tokamaks EAST (China) and K-STAR (Korea). ECRH results in the 1980s and beyond progressed rapidly with the development of gyrotron sources at the MW level and subsequently efficient heating and current drive was demonstrated on DIII-D, Asdex-U, JT-60U and TCV, including the stabilization of neoclassical tearing modes. Recent gyrotron tube development at the MW level at 170 GHz ensures the availability of ECH and ECCD on ITER. Finally, new results on RF induced transport phenomena have been discovered, such as enhanced plasma rotation and flow drive that hold promise for optimizing ITER performance.

  5. Initial operation of a newly developed multichord motional Stark effect diagnostic in KSTAR

    NASA Astrophysics Data System (ADS)

    Chung, J.; Ko, J.; Wi, H.; Messmer, M.; Schenkelaars, S.; Scheffer, M.; Jaspers, R. J. E.

    2016-11-01

    A photo-elastic modulator based 25-chord motional Stark effect (MSE) diagnostic has been successfully developed and commissioned in Korea Superconducting Tokamak Advanced Research. The diagnostic measures the radial magnetic pitch angle profile of the Stark splitting of a D-alpha line at 656.1 nm by the electric field associated with the neutral deuterium heating beam. A tangential view of the neutral beam provides a good spatial resolution of 1-3 cm for covering the major radius from 1.74 m to 2.28 m, and the time resolution is achieved at 10 ms. An in-vessel calibration before the vacuum closing as well as an in situ calibration during the tokamak operation was performed by means of specially designed polarized lighting sources. In this work, we present the final design of the installed MSE diagnostic and the first results of the commissioning.

  6. Development of a neural network technique for KSTAR Thomson scattering diagnostics

    NASA Astrophysics Data System (ADS)

    Lee, Seung Hun; Lee, J. H.; Yamada, I.; Park, Jae Sun

    2016-11-01

    Neural networks provide powerful approaches of dealing with nonlinear data and have been successfully applied to fusion plasma diagnostics and control systems. Controlling tokamak plasmas in real time is essential to measure the plasma parameters in situ. However, the χ2 method traditionally used in Thomson scattering diagnostics hampers real-time measurement due to the complexity of the calculations involved. In this study, we applied a neural network approach to Thomson scattering diagnostics in order to calculate the electron temperature, comparing the results to those obtained with the χ2 method. The best results were obtained for 103 training cycles and eight nodes in the hidden layer. Our neural network approach shows good agreement with the χ2 method and performs the calculation twenty times faster.

  7. Status of motional Stark effect and Zeeman effect diagnostics for KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, Jinseok; Chung, Jinil; de Bock, Maarten; KSTAR Team

    2014-10-01

    The motional Stark effect (MSE) diagnostic system is under development aiming at commissioning in 2015. The design and fabrication of the polarization preserving front optics has been complete, including the multi-layer dielectric coated mirror and beam splitter, the latter being required to split the incident light into that above 600 nm for MSE and that below 600 nm for the Charge Exchange Spectroscopy (CES) that shares the front optics with MSE. The bandpass filters with a sharp transmission function and a minimum distortion against tilting have been procured. Both the analog lock-in and the post-processing numerical Fourier transform will be exploited. The Li-beam based Zeeman effect (ZE) diagnostic system is under conceptual design. Its details on the design are introduced in this work including the radial resolution and sensitivity to the change of the magnetic field pitch near the pedestal region. Work supported by the Ministry of Science, ICT and Future Planning, Korea.

  8. Development of fast neutron pinhole camera using nuclear emulsion for neutron emission profile measurement in KSTAR

    NASA Astrophysics Data System (ADS)

    Izumi, Y.; Tomita, H.; Nakayama, Y.; Hayashi, S.; Morishima, K.; Isobe, M.; Cheon, M. S.; Ogawa, K.; Nishitani, T.; Naka, T.; Nakano, T.; Nakamura, M.; Iguchi, T.

    2016-11-01

    We have developed a compact fast neutron camera based on a stack of nuclear emulsion plates and a pinhole collimator. The camera was installed at J-port of Korea superconducting tokamak advanced research at National Fusion Research Institute, Republic of Korea. Fast neutron images agreed better with calculated ones based on Monte Carlo neutron simulation using the uniform distribution of Deuterium-Deuterium (DD) neutron source in a torus of 40 cm radius.

  9. The first experimental results from x-ray imaging crystal spectrometer for KSTAR

    SciTech Connect

    Lee, S. G.; Bak, J. G.; Nam, U. W.; Moon, M. K.; Shi, Y.; Bitter, M.; Hill, K.

    2010-10-15

    The x-ray imaging crystal spectrometer (XICS) for the Korea Superconducting Tokamak Advanced Research has been first applied for the experimental campaign in 2009. The XICS was designed to provide measurements of the profiles of the ion and electron temperatures from the heliumlike argon (Ar XVII) spectra. The basic functions of the XICS are properly working although some satellites lines are not well matched with the expected theoretical values. The initial experimental results from the XICS are briefly described.

  10. Cerenkov ring imaging and spectroscopy of charged KSTAR interactions at 11 GeV/c

    SciTech Connect

    Bird, P.F.

    1988-11-01

    The physics and technology of this new Cerenkov detector are discussed, including materials studies, construction techniques, and resolution measurements. Sources of resolution error are individually identified and measured where possible. The results of all studied indicate that the measurement resolution is understood. This work has led to the adoption of a large scale ring imaging detector as part of a new high energy physics spectrometer, the SLD, at the Stanford Linear Accelerator Center. Results from an amplitude analysis of strange meson final states in K/sup /minus//p ..-->.. /ovr K/sub 0//..pi../sup /minus//p interactions are presented. The data derive from a 4 event/nb exposure of the LASS (large Aperture Superconducting Solenoid) spectrometer to an 11 GeV/c K/sup /minus// beam. The data sample consists of /approximately/100,000 vents distributed over the Dalitz plot of the channel. The process is observed to be dominated by the production and decay of natural spin-parity (J/sup P/ = 1/sup /minus//,2/sup +/,3/sup /minus//,/hor ellipsis/) strange meson states. The data can be understood in terms of a simple model in which the resonant /ovr K*/sup -// are produced predominantly via natural parity exchange in the t channel. The leading K*(890), K/sub 2/*(1430), and K*(1780) resonances are clearly observed and measured, and the underlying spectroscopy is also extracted. Indications of higher mass resonance production are also shown. The observed properties of these states are used to confront current models of quark spectroscopy in strange meson systems. 94 refs., 96 figs., 23 tabs.

  11. New compact and efficient local oscillator optic system for the KSTAR electron cyclotron emission imaging system

    NASA Astrophysics Data System (ADS)

    Nam, Y. B.; Lee, D. J.; Lee, J.; Kim, C.; Yun, G. S.; Lee, W.; Park, H. K.

    2016-11-01

    Electron cyclotron emission imaging (ECEI) diagnostic on Korean Superconducting Tokamak Advanced Research utilizes quasi-optical heterodyne-detection method to measure 2D (vertical and radial) Te fluctuations from two toroidally separated poloidal cross section of the plasma. A cylindrical lens local oscillator (LO) optics with optical path length (OPL) 2-2.5 m has been used in the current ECEI system to couple the LO source to the 24 vertically aligned array of ECE detectors. For efficient and compact LO optics employing the Powell lens is proposed so that the OPL of the LO source is significantly reduced from ˜2.0 m to 0.4 m with new optics. The coupling efficiency of the LO source is expected to be improved especially at the edge channels. Results from the optical simulation together with the laboratory test of the prototype optics will be discussed in this paper.

  12. Numerical simulation for the accelerator of the KSTAR neutral beam ion source.

    PubMed

    Kim, Tae-Seong; Jeong, Seung Ho; In, Sang Ryul

    2010-02-01

    Recent experiments with a prototype long-pulse, high-current ion source being developed for the neutral beam injection system of the Korea Superconducting Tokamak Advanced Research have shown that the accelerator grid assembly needs a further upgrade to achieve the final goal of 120keV/65A for the deuterium ion beam. The accelerator upgrade concept was determined theoretically by simulations using the IGUN code. The simulation study was focused on finding parameter sets that raise the optimum perveance as large as possible and reduce the beam divergence as low as possible. From the simulation results, it was concluded that it is possible to achieve this goal by sliming the plasma grid (G1), shortening the second gap (G2-G3), and adjusting the G2 voltage ratio.

  13. Design and fabrication of a multi-purpose soft x-ray array diagnostic system for KSTAR

    SciTech Connect

    Lee, Seung Hun; Chai, Kil Byoung; Jang, Siwon; Choe, Wonho; Ko, Won-Ha; Kim, Junghee; Seo, Dongcheol; Lee, Jongha; Bogatu, I. N.; Kim, Jin-Soo

    2012-10-15

    A multi-purpose soft x-ray array diagnostic system was developed for measuring two-dimensional x-ray emissivity profile, electron temperature, Ar impurity transport, and total radiation power. A remotely controlled filter wheel was designed with three different choices of filters. The electron temperature profile can be determined from the ratio of two channels having different thickness of Be layer, and the Ar impurity concentration transport can be determined from a pair of Ar Ross filters (CaF{sub 2} and NaCl thin films). Without any filters, this diagnostic system can also be used as a bolometer.

  14. Experimental results from an X-ray imaging crystal spectrometer utilizing multi-wire proportional counter for KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, S. G.; Yoo, J. W.; Kim, Y. S.; Nam, U. W.; Moon, M. K.

    2016-11-01

    The inconsistency of the first experimental results from the X-ray imaging crystal spectrometer for the Korea Superconducting Tokamak Advanced Research device utilizing a multi-wire proportional counter (MWPC) is clarified after improving the photon-count rate of the data acquisition system for the MWPC and ground loop isolator for the whole spectrometer system. The improved MWPC is successfully applied to pure Ohmic plasmas as well as plasmas with high confinement modes.

  15. Design and fabrication of a multi-purpose soft x-ray array diagnostic system for KSTAR.

    PubMed

    Lee, Seung Hun; Chai, Kil Byoung; Jang, Siwon; Ko, Won-Ha; Kim, Junghee; Seo, Dongcheol; Lee, Jongha; Bogatu, I N; Kim, Jin-Soo; Choe, Wonho

    2012-10-01

    A multi-purpose soft x-ray array diagnostic system was developed for measuring two-dimensional x-ray emissivity profile, electron temperature, Ar impurity transport, and total radiation power. A remotely controlled filter wheel was designed with three different choices of filters. The electron temperature profile can be determined from the ratio of two channels having different thickness of Be layer, and the Ar impurity concentration transport can be determined from a pair of Ar Ross filters (CaF(2) and NaCl thin films). Without any filters, this diagnostic system can also be used as a bolometer.

  16. Fusion Research in Ioffe Institute

    NASA Astrophysics Data System (ADS)

    Askinazi, L. G.; Afanasyev, V. I.; Altukhov, A. B.; Bakharev, N. N.; Belokurov, A. A.; Bulanin, V. V.; Bykov, A. S.; Chernyshev, F. V.; Chugunov, I.; Dyachenko, V. V.; Esipov, L. A.; Gin, D.; Goncharov, P. R.; Gurchenko, A. D.; Gusakov, E. Z.; Gusev, V. K.; Heuraux, S.; Iblyaminova, A. D.; Irzak, M. A.; Kantor, M. Yu.; Kaveeva, E. G.; Kiviniemi, T.; Khilkevitch, E. M.; Khitrov, S. A.; Khromov, N. A.; Kornev, V. A.; Kouprienko, D. V.; Kurskiev, G. S.; Lashkul, S. I.; Lebedev, S. V.; Leerink, S.; Melnik, A. D.; Minaev, V. B.; Mironov, M. I.; Miroshnikov, I. V.; Mukhin, E. E.; Nesenevich, V. G.; Niskala, P.; Novokhatsky, A. N.; Patrov, M. I.; Perevalov, A. A.; Petrov, M. P.; Petrov, A. V.; Petrov, Yu. V.; Popov, A. Yu.; Rozhansky, V. A.; Rozhdestvenskiy, V. V.; Sakharov, N. V.; Saveliev, A. N.; Senichenkov, I. Yu.; Sergeev, V. Yu.; Shchegolev, P. B.; Shatalin, S. V.; Shcherbinin, O. N.; Shevelev, A. E.; Sidorov, A. V.; da Silva, F.; Smirnov, A. I.; Stepanov, A. Yu.; Sysoeva, E. V.; Teplova, N. V.; Tolstyakov, S. Yu.; Tukachinsky, A. S.; Varfolomeev, V. I.; Vekshina, E. O.; Vildjunas, M. I.; Voronin, A. V.; Voskoboinikov, S. P.; Wagner, F.; Yashin, A. Yu.; Zhubr, N. A.

    2015-10-01

    In this paper we present the fusion related activities of the Plasma Physics Division at the Ioffe Institute. The first experiments on lower hybrid current drive (LHCD) in a spherical tokamak performed at the Globus-M tokamak (R = 0.36 m, a = 0.24 m, Bt = 0.4 T, Ip = 200 kA) with a novel poloidally oriented grill resulted in an RF driven current of up to 30 kA at (100 kW, 2.5 GHz), exceeding the modelling predictions. At the FT-2 tokamak (R = 0.56 m, a = 0.08 m, Bt = 3 T, Ip = 30 kA) experiments with a traditional toroidally oriented grill revealed no strong dependence of the LHCD density limit on the H/D ratio in spite of LH resonance densities differing by a factor of 3. Microwave Doppler reflectometry (DR) at the Globus-M, and DR and heavy ion beam probe measurements at the tokamak TUMAN-3M (R = 0.53 m, a = 0.24 m, Bt = 1.0 T, Ip = 190 kA) demonstrated geodesic acoustic mode (GAM) suppression at the L to H transition. Observations at FT-2 using Doppler Enhanced Scattering showed that the GAM amplitude is anti-correlated both spatially and temporally to the drift turbulence level and electron thermal diffusivity. For the first time turbulence amplitude modulation at the GAM frequency was found both experimentally and in global gyrokinetic modelling. A model of the L-H transition is proposed based on this effect. The loss mechanisms of energetic ions' (EI) were investigated in the neutral beam injection (NBI) experiments on Globus-M and TUMAN-3M. Empirical scaling of the 2.45 MeV DD neutron rate for the two devices shows a strong dependence on toroidal field Bt1.29 and plasma current Ip1.34 justifying the Bt and Ip increase by a factor of 2.5 for the proposed upgrade of Globus-M. Bursts of ˜1 MHz Alfvenic type oscillations correlating with sawtooth crashes were observed in ohmic TUMAN-3M discharges. The possibility of low threshold parametric excitation of Bernstein and upper hybrid waves trapped in drift-wave eddies resulting in anomalous absorption in electron

  17. Full wave effects on the lower hybrid wave spectrum and driven current profile in tokamak plasmas

    SciTech Connect

    Shiraiwa, S.; Ko, J.; Meneghini, O.; Parker, R.; Schmidt, A. E.; Greenwald, M.; Hubbard, A. E.; Hughes, J.; Ma, Y.; Podpaly, Y.; Rice, J. E.; Wallace, G.; Wolfe, S. M.; C-Mod Group, Alcator; Scott, S.; Wilson, J. R.

    2011-08-15

    A numerical modeling of current profile modification by lower hybrid current drive (LHCD) using a fullwave/Fokker-Planck simulation code is presented. A MHD stable LHCD discharge on Alcator C-Mod was analyzed, and the current profile from full wave simulations was found to show better agreement with the experiment than a ray-tracing code. Comparison of full wave and ray-tracing simulation shows that, although ray-tracing can reproduce the stochastic wave spectrum broadening, the full wave calculation predicts even wider spectrum broadening, and the wave spectrum fills all of the kinematically allowed domain. This is the first demonstration of LHCD current profile modeling using a full wave simulation code in a multi-pass absorption regime, showing the clear impact of full wave effects on the LHCD driven current profile.

  18. Experimental characterization and modelling of non-linear coupling of the lower hybrid current drive power on Tore Supra

    NASA Astrophysics Data System (ADS)

    Preynas, M.; Goniche, M.; Hillairet, J.; Litaudon, X.; Ekedahl, A.; Colas, L.

    2013-01-01

    To achieve steady-state operation on future fusion devices, in particular on ITER, the coupling of the lower hybrid wave must be optimized on a wide range of edge conditions. However, under some specific conditions, deleterious effects on the lower hybrid current drive (LHCD) coupling are sometimes observed on Tore Supra. In this way, dedicated LHCD experiments have been performed using the LHCD system of Tore Supra, composed of two different conceptual designs of launcher: the fully active multi-junction (FAM) and the new passive active multi-junction (PAM) antennas. A non-linear interaction between the electron density and the electric field has been characterized in a thin plasma layer in front of the two LHCD antennas. The resulting dependence of the power reflection coefficient (RC) with the LHCD power is not predicted by the standard linear theory of the LH wave coupling. A theoretical model is suggested to describe the non-linear wave-plasma interaction induced by the ponderomotive effect and implemented in a new full wave LHCD code, PICCOLO-2D (ponderomotive effect in a coupling code of lower hybrid wave-2D). The code self-consistently treats the wave propagation in the antenna vicinity and its interaction with the local edge plasma density. The simulation reproduces very well the occurrence of a non-linear behaviour in the coupling observed in the LHCD experiments. The important differences and trends between the FAM and the PAM antennas, especially a larger increase in RC for the FAM, are also reproduced by the PICCOLO-2D simulation. The working hypothesis of the contribution of the ponderomotive effect in the non-linear observations of LHCD coupling is therefore validated through this comprehensive modelling for the first time on the FAM and PAM antennas on Tore Supra.

  19. Optical system design for the charge exchange spectroscopy of the Korea superconducting tokamak advanced research device

    NASA Astrophysics Data System (ADS)

    Oh, Seungtae; Ko, Won-Ha

    2011-04-01

    The collective optical design is described for the charge exchange spectroscopy (CES) of the Korea superconducting tokamak advanced research (KSTAR) device. The CES diagnostic measures the ion temperature of carbon and other impurities, in conjunction with the neutral heating beam in KSTAR. The visible light from the plasma is concentrated via collection optics and imaged onto quartz fibers. The collection optics in the system is the key component for the CES system. The final design is derived through four steps and its performance is examined in a simulation step. In this paper, the design details of the collective optical system for the KSTAR CES are discussed.

  20. Lower hybrid current drive and ion cyclotron range of frequencies heating experiments in H-mode plasmas in Experimental Advanced Superconducting Tokomak

    NASA Astrophysics Data System (ADS)

    Zhang, X. J.; Wan, B. N.; Zhao, Y. P.; Ding, B. J.; Xu, G. S.; Gong, X. Z.; Li, J. G.; Lin, Y.; Taylor, G.; Noterdaeme, J. M.; Braun, F.; Wukitch, S.; Magne, R.; Litaudon, X.; Kumazawa, R.; Kasahara, H.

    2014-06-01

    An ion cyclotron range of frequencies (ICRF) system with power up to 6.0 MW and a lower hybrid current drive (LHCD) system up to 4 MW have been applied for heating and current drive experiments in Experimental Advanced Superconducting Tokomak (EAST). Significant progress has been made with ICRF heating and LHCD for realizing the H-mode plasma operation in EAST. During 2010 and 2012 experimental campaigns, ICRF heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H minority heating (H-MH) mode. The H-MH mode produced good plasma performance, and realized H-mode using ICRF power alone in 2012. In 2010, H-modes were generated and sustained by LHCD alone, where lithium coating and gas puffing near the mouth of the LH launcher were applied to improve the LHCD power coupling and penetration into the core plasmas of H-modes. In 2012, the combination of LHCD and ICRH power extended the H-mode duration up to over 30 s. H-modes with various types of edge localized modes (ELMs) have been achieved with HIPB98(y, 2) ranging from 0.7 to over unity. A brief overview of LHCD and ICRF Heating experiment and their application in achieving H-mode operation during these two campaigns will be presented.

  1. Lower hybrid current drive in experiments for transport barriers at high {beta}{sub N} of JET (Joint European Torus)

    SciTech Connect

    Cesario, R. C.; Castaldo, C.; De Angelis, R.; Smeulders, P.; Calabro, G.; Pericoli, V.; Ravera, G.

    2007-09-28

    LHCD has been used in JET experiments aimed at producing internal transport barriers (ITBs) in highly triangular plasmas ({delta}{approx_equal}0.4) at high {beta}{sub N} (up to 3) for steady-state application. The LHCD is a potentially valuable tool for (i) modifying the target q-profile, which can help avoid deleterious MHD modes and favour the formation of ITBs, and (ii) contributing to the non-inductive current drive required to prolong such plasma regimes. The q-profile evolution has been simulated during the current ramp-up phase for such a discharge (B{sub 0} = 2.3 T, I{sub P} = 1.5 MA) where 2 MW of LHCD has been coupled. The JETTO code was used taking measured plasma profiles, and the LHCD profile modeled by the LHstar code. The results are in agreement with MSE measurements and indicate the importance of the elevated electron temperature due to LHCD, as well as the driven current. During main heating with 18 MW of NBI and 3 MW of ICRH the bootstrap current density at the edge also becomes large, consistently with the observed reduction of the local turbulence and of the MHD activity. JETTO modelling suggests that the bootstrap current can reduce the magnetic shear (sh) at large radius, potentially affecting the MHD stability and turbulence behaviour in this region. Keywords: lower hybrid current drive (LHCD), bootstrap current, q (safety factor) and shear (sh) profile evolutions.

  2. Lower hybrid current drive and ion cyclotron range of frequencies heating experiments in H-mode plasmas in Experimental Advanced Superconducting Tokomak

    SciTech Connect

    Zhang, X. J.; Wan, B. N. Zhao, Y. P.; Ding, B. J.; Xu, G. S.; Gong, X. Z.; Li, J. G.; Lin, Y.; Wukitch, S.; Taylor, G.; Noterdaeme, J. M.; Braun, F.; Magne, R.; Litaudon, X.; Kumazawa, R.; Kasahara, H.

    2014-06-15

    An ion cyclotron range of frequencies (ICRF) system with power up to 6.0 MW and a lower hybrid current drive (LHCD) system up to 4 MW have been applied for heating and current drive experiments in Experimental Advanced Superconducting Tokomak (EAST). Significant progress has been made with ICRF heating and LHCD for realizing the H-mode plasma operation in EAST. During 2010 and 2012 experimental campaigns, ICRF heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H minority heating (H-MH) mode. The H-MH mode produced good plasma performance, and realized H-mode using ICRF power alone in 2012. In 2010, H-modes were generated and sustained by LHCD alone, where lithium coating and gas puffing near the mouth of the LH launcher were applied to improve the LHCD power coupling and penetration into the core plasmas of H-modes. In 2012, the combination of LHCD and ICRH power extended the H-mode duration up to over 30 s. H-modes with various types of edge localized modes (ELMs) have been achieved with H{sub IPB98}(y, 2) ranging from 0.7 to over unity. A brief overview of LHCD and ICRF Heating experiment and their application in achieving H-mode operation during these two campaigns will be presented.

  3. Steady state plasma operation in RF dominated regimes on EAST

    SciTech Connect

    Zhang, X. J.; Zhao, Y. P.; Gong, X. Z.; Hu, C. D.; Liu, F. K.; Hu, L. Q.; Wan, B. N. Li, J. G.

    2015-12-10

    Significant progress has recently been made on EAST in the 2014 campaign, including the enhanced CW H&CD system over 20MW heating power (LHCD, ICRH and NBI), more than 70 diagnostics, ITER-like W-monoblock on upper divertor, two inner cryo-pumps and RMP coils, enabling EAST to investigate long pulse H mode operation with dominant electron heating and low torque to address the critical issues for ITER. H-mode plasmas were achieved by new H&CD system or 4.6GHz LHCD alone for the first time. Long pulse high performance H mode has been obtained by LHCD alone up to 28s at H{sub 98}∼1.2 or by combing of ICRH and LHCD, no or small ELM was found in RF plasmas, which is essential for steady state operation in the future Tokamak. Plasma operation in low collision regimes were implemented by new 4.6GHz LHCD with core Te∼4.5keV. The non-inductive scenarios with high performance at high bootstrap current fraction have been demonstrated in RF dominated regimes for long pulse operation. Near full non-inductive CD discharges have been achieved. In addition, effective heating and decoupling method under multi-transmitter for ICRF system were developed in this campaign, etc. EAST could be in operation with over 30MW CW heating and current drive power (LHCD ICRH NBI and ECRH), enhanced diagnostic capabilities and full actively-cooled metal wall from 2015. It will therefore allow to access new confinement regimes and to extend these regimes towards to steady state operation.

  4. Studies on LH-generated Fast Electron Tail Using the Oblique ECE Diagnostic at JET

    SciTech Connect

    Sozzi, C.; Grossetti, G.; Farina, D.; Figini, L.; Garavaglia, S.; Nowak, S.; Baranov, Y.; Kirov, K.; Luna, E. de la

    2009-11-26

    The new Oblique ECE diagnostics of JET allows simultaneous measurement along three lines of sight at different toroidal angles. JET pulses, in which modulated LHCD power was applied, were analyzed by means of the SPECE emission code, which takes into account the fast electron tail generated by LH. The code results were compared to the ECE spectra from the oblique ECE diagnostic. The match between the computed and the experimental data from the three lines of sight provides an estimate of the density of superthermal electrons and of their maximum energy from which the fraction of the plasma current driven by LHCD is derived.

  5. Study of lower hybrid current drive towards long-pulse operation with high performance in EAST

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Li, M. H.; Li, Y. C.; Wang, M.; Shan, J. F.; Liu, F. K.; Wang, S. L.; Wei, W.; Xu, H. D.; Zhao, L. M.; Hu, H. C.; Jia, H.; Cheng, M.; Yang, Y.; Liu, L.; Xu, G. S.; Zang, Q.; Zhao, H. L.; Peysson, Y.; Decker, J.; Goniche, M.; Cesario, R.; Amicucci, L.; Tuccillo, A. A.; Baek, G. S.; Parker, R.; Bonoli, P. T.; Yang, C.; Zhao, Y. P.; Qian, J. P.; Gong, X. Z.; Hu, L. Q.; Li, J. G.; Wan, B. N.

    2015-12-01

    High density experiments with 2.45 GHz lower hybrid current drive (LHCD) in EAST are analyzed by means of simulation and modeling, showing that parametric instabilities (PI), collisional absorption and density fluctuations in the edge region could be responsible for the low CD efficiency at high density. In addition, recent LHCD results with 4.6 GHz are presented, showing that lower hybrid wave can be coupled to plasma with low reflection coefficient, drive plasma current and modify the current profile, and heat plasma effectively. The related results between two systems (2.45 GHz and 4.6 GHz) are also compared, including CD efficiency and PI behavior.

  6. 47 CFR 25.146 - Licensing and operating rules for the non-geostationary orbit Fixed-Satellite Service in the 10.7...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...-geostationary orbit Fixed-Satellite Service in the 10.7 GHz-14.5 GHz bands. 25.146 Section 25.146 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS... Fixed-Satellite Service in the 10.7 GHz-14.5 GHz bands. (a) A comprehensive technical showing shall...

  7. 78 FR 72851 - Commission Seeks Comment on Licensing Models and Technical Requirements in the 3550-3650 MHz Band

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-04

    ... Commission's Public Notice in GN Docket No. 12-354, FCC 13-144A1, Notice of Proposed Rulemaking, 78 FR 1188... Proceedings, 63 FR 24121 (1998). Electronic Filers: Comments may be filed electronically using the Internet by... deployment while protecting existing incumbent users of the 3.5 GHz Band. See 3.5 GHz NPRM, 78 FR 1188....

  8. Design of a Doppler reflectometer for KSTARa)

    NASA Astrophysics Data System (ADS)

    Lee, K. D.; Nam, Y. U.; Seo, Seong-Heon; Kim, Y. S.

    2014-11-01

    A Doppler reflectometer has been designed to measure the poloidal propagation velocity on the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. It has the operating frequency range of V-band (50-75 GHz) and the monostatic antenna configuration with extraordinary mode (X-mode). The single sideband modulation with an intermediate frequency of 50 MHz is used for the heterodyne measurement with the 200 MHz in-phase and quadrature (I/Q) phase detector. The corrugated conical horn antenna is used to approximate the Gaussian beam propagation and it is installed together with the oversized rectangular waveguides in the vacuum vessel. The first commissioning test of the Doppler reflectometer system on the KSTAR tokamak is planned in the 2014 KSTAR experimental campaign.

  9. Control of the current density profile with lower hybrid current drive on PBX-M

    SciTech Connect

    Bell, R.E.; Bernabei, S.; Chu, T.K.; Gettelfinger, G.; Greenough, N.; Hatcher, R.; Ignat, D.; Jardin, S.; Kaita, R.; Kaye, S.; Kozub, T.; Kugel, H.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Sauthoff, N.; Sesnic, S.; Sun, Y.; Takahashi, H.; Tighe, W.; Valeo, E.; von Goeler, S.; Blush, L.; Doerner, R.; Schmitz, L.; Tynan, G.; Dunlap, J.; England, A.; Harris, J.; Hirshman, S.; Isler, R.; Lee, D.; Jones, S.; Kesner, J.; Luckhardt, S.; Paoletti, F.; Levinton, F.; Timini, F.

    1993-07-01

    Lower hybrid current drive (LHCD) is being explored as a means to control the current density profile on PBX-M with the goal of raising the central safety factor q(O) to values of 1.5-2 to facilitate access to a full-volume second stable regime. Initial experiments have been conducted with up to 400 kW of 4.6 GHz LH power in circular and indented plasmas with modest parameters. A tangential-viewing two-dimensional hard x-ray imaging diagnostic has been used to observe the bremsstrahlung emission from the suprathermal electrons generated during LHCD. Hollow hard x-ray images have indicated off-axis localization of the driven current. A serious obstacle to the control of the current density profile with LHCD is the concomitant generation of MHD activity, which can seriously degrade the confinement of suprathermal electrons. By combining neutral beam injection with LHCD, an MHD-free condition has been obtained where q(O) is raised above 1.

  10. Comparative modelling of lower hybrid current drive with two launcher designs in the Tore Supra tokamak

    NASA Astrophysics Data System (ADS)

    Nilsson, E.; Decker, J.; Peysson, Y.; Artaud, J.-F.; Ekedahl, A.; Hillairet, J.; Aniel, T.; Basiuk, V.; Goniche, M.; Imbeaux, F.; Mazon, D.; Sharma, P.

    2013-08-01

    Fully non-inductive operation with lower hybrid current drive (LHCD) in the Tore Supra tokamak is achieved using either a fully active multijunction (FAM) launcher or a more recent ITER-relevant passive active multijunction (PAM) launcher, or both launchers simultaneously. While both antennas show comparable experimental efficiencies, the analysis of stability properties in long discharges suggest different current profiles. We present comparative modelling of LHCD with the two different launchers to characterize the effect of the respective antenna spectra on the driven current profile. The interpretative modelling of LHCD is carried out using a chain of codes calculating, respectively, the global discharge evolution (tokamak simulator METIS), the spectrum at the antenna mouth (LH coupling code ALOHA), the LH wave propagation (ray-tracing code C3PO), and the distribution function (3D Fokker-Planck code LUKE). Essential aspects of the fast electron dynamics in time, space and energy are obtained from hard x-ray measurements of fast electron bremsstrahlung emission using a dedicated tomographic system. LHCD simulations are validated by systematic comparisons between these experimental measurements and the reconstructed signal calculated by the code R5X2 from the LUKE electron distribution. An excellent agreement is obtained in the presence of strong Landau damping (found under low density and high-power conditions in Tore Supra) for which the ray-tracing model is valid for modelling the LH wave propagation. Two aspects of the antenna spectra are found to have a significant effect on LHCD. First, the driven current is found to be proportional to the directivity, which depends upon the respective weight of the main positive and main negative lobes and is particularly sensitive to the density in front of the antenna. Second, the position of the main negative lobe in the spectrum is different for the two launchers. As this lobe drives a counter-current, the resulting

  11. Lower hybrid current drive at high density in the multi-pass regimea)

    NASA Astrophysics Data System (ADS)

    Wallace, G. M.; Faust, I. C.; Meneghini, O.; Parker, R. R.; Shiraiwa, S.; Baek, S. G.; Bonoli, P. T.; Hubbard, A. E.; Hughes, J. W.; LaBombard, B. L.; Lau, C.; Ma, Y.; Reinke, M. L.; Terry, J. L.; Whyte, D. G.; Wright, J. C.; Wukitch, S. J.; Harvey, R. W.; Schmidt, A. E.; Smirnov, A. P.; Wilson, J. R.

    2012-06-01

    Assessing the performance of lower hybrid current drive (LHCD) at high density is critical for developing non-inductive current drive systems on future steady-state experiments. Excellent LHCD efficiency has been observed during fully non-inductive operation (η =2.0-2.5×1019 AW-1m-2 at n¯e=0.5×1020 m-3) on Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] under conditions (ne, magnetic field and topology, and LHCD frequency) relevant to ITER [S. Shiraiwa et al., Nucl. Fusion 51, 103024 (2011)]. To extend these results to advanced tokamak regimes with higher bootstrap current fractions on C-Mod, it is necessary to increase n ¯e to 1.0-1.5×1020 m-3. However, the number of current-carrying, non-thermal electrons generated by LHCD drops sharply in diverted configurations at densities that are well below the density limit previously observed on limited tokamaks. In these cases, changes in scrape off layer (SOL) ionization and density profiles are observed during LHCD, indicating that significant power is transferred from the LH waves to the SOL. Fokker-Planck simulations of these discharges utilizing ray tracing and full wave propagation codes indicate that LH waves in the high density, multi-pass absorption regime linger in the plasma edge, and SOL region, where absorption near or outside the LCFS results in the loss of current drive efficiency. Modeling predicts that non-thermal emission increases with stronger single-pass absorption. Experimental data show that increasing Te in high density LH discharges results in higher non-thermal electron emission, as predicted by the models.

  12. Lower hybrid current drive at high density in the multi-pass regime

    SciTech Connect

    Wallace, G. M.; Faust, I. C.; Meneghini, O.; Parker, R. R.; Shiraiwa, S.; Baek, S. G.; Bonoli, P. T.; Hubbard, A. E.; Hughes, J. W.; LaBombard, B. L.; Lau, C.; Ma, Y.; Reinke, M. L.; Terry, J. L.; Whyte, D. G.; Wright, J. C.; Wukitch, S. J.; Schmidt, A. E.; Harvey, R. W.; Smirnov, A. P.; and others

    2012-06-15

    Assessing the performance of lower hybrid current drive (LHCD) at high density is critical for developing non-inductive current drive systems on future steady-state experiments. Excellent LHCD efficiency has been observed during fully non-inductive operation ({eta}=2.0-2.5 Multiplication-Sign 10{sup 19} AW{sup -1}m{sup -2} at n{sub e}=0.5 Multiplication-Sign 10{sup 20} m{sup -3}) on Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] under conditions (n{sub e}, magnetic field and topology, and LHCD frequency) relevant to ITER [S. Shiraiwa et al., Nucl. Fusion 51, 103024 (2011)]. To extend these results to advanced tokamak regimes with higher bootstrap current fractions on C-Mod, it is necessary to increase n{sub e} to 1.0-1.5 Multiplication-Sign 10{sup 20} m{sup -3}. However, the number of current-carrying, non-thermal electrons generated by LHCD drops sharply in diverted configurations at densities that are well below the density limit previously observed on limited tokamaks. In these cases, changes in scrape off layer (SOL) ionization and density profiles are observed during LHCD, indicating that significant power is transferred from the LH waves to the SOL. Fokker-Planck simulations of these discharges utilizing ray tracing and full wave propagation codes indicate that LH waves in the high density, multi-pass absorption regime linger in the plasma edge, and SOL region, where absorption near or outside the LCFS results in the loss of current drive efficiency. Modeling predicts that non-thermal emission increases with stronger single-pass absorption. Experimental data show that increasing T{sub e} in high density LH discharges results in higher non-thermal electron emission, as predicted by the models.

  13. Impact of resistive MHD plasma response on perturbation field sidebands

    NASA Astrophysics Data System (ADS)

    Orlov, D. M.; Evans, T. E.; Moyer, R. A.; Lyons, B. C.; Ferraro, N. M.; Park, G.-Y.

    2016-07-01

    Single fluid linear simulations of a KSTAR RMP ELM suppressed discharge with the M3D-C1 resistive magnetohydrodynamic code have been performed for the first time. The simulations show that the application of the n  =  1 perturbation using the KSTAR in-vessel control coils (IVCC), which apply modest levels of n  =  3 sidebands (~20% of the n  =  1), leads to levels of n  =  3 sideband that are comparable to the n  =  1 when plasma response is included. This is due to the reduced level of screening of the rational-surface-resonant n  =  3 component relative to the rational-surface-resonant n  =  1 component. The n  =  3 sidebands could play a similar role in ELM suppression on KSTAR as the toroidal sidebands (n  =  1, 2, 4) in DIII-D n  =  3 ELM suppression with missing I-coil segments (Paz Soldan et al 2014 Nucl. Fusion 54 073013). This result may help to explain the uniqueness of ELM suppression with n  =  1 perturbations in KSTAR since the effective perturbation is a mixed n  =  1/n  =  3 perturbation similar to n  =  3 ELM suppression in DIII-D.

  14. Doppler Sideband Spectra for Ions in a Linear Trap

    NASA Technical Reports Server (NTRS)

    Prestage, J. D.; Tjoelker, R. L.; Dick, G. J.; Maleki, L.

    1993-01-01

    We describe a spectroscopic measurement of the temperature and linear density of HG+ ions held in a linear ion trap (LIT). The inferred temperature and number result from analysis of sidebands on the 40.5 GHz resonance line.

  15. Microwave Radiation Detector

    NASA Technical Reports Server (NTRS)

    Lesh, J. R.

    1984-01-01

    Direct photon detector responds to microwave frequencies. Method based on trapped-ion frequency-generation standards proposed to detect radio-frequency (RF) radiation at 40.5 GHz. Technique used for directdetection (RF) communication, radar, and radio astronomy.

  16. 77 FR 44614 - Information Collection(s) Being Reviewed by the Federal Communications Commission

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-30

    ... will be expanded to add ``LTE'', ``Wi-FI'', ``WiMax'', ``2.4 GHz'', and ``2.5 GHz''. In addition, the... the 2011 ANSI standard without testing VoLTE transmissions. Federal Communications Commission. Bulah...

  17. Broadband and tunable high-performance microwave absorption of an ultralight and highly compressible graphene foam.

    PubMed

    Zhang, Yi; Huang, Yi; Zhang, Tengfei; Chang, Huicong; Xiao, Peishuang; Chen, Honghui; Huang, Zhiyu; Chen, Yongsheng

    2015-03-25

    The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated. Simply via physical compression, the microwave absorption performance can be tuned. The qualified bandwidth coverage of 93.8% (60.5 GHz/64.5 GHz) is achieved for the GF under 90% compressive strain (1.0 mm thickness). This mainly because of the 3D conductive network. PMID:25689269

  18. Broadband and tunable high-performance microwave absorption of an ultralight and highly compressible graphene foam.

    PubMed

    Zhang, Yi; Huang, Yi; Zhang, Tengfei; Chang, Huicong; Xiao, Peishuang; Chen, Honghui; Huang, Zhiyu; Chen, Yongsheng

    2015-03-25

    The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated. Simply via physical compression, the microwave absorption performance can be tuned. The qualified bandwidth coverage of 93.8% (60.5 GHz/64.5 GHz) is achieved for the GF under 90% compressive strain (1.0 mm thickness). This mainly because of the 3D conductive network.

  19. Cygnus X-2 in a radio quiet state

    NASA Astrophysics Data System (ADS)

    Rushton, A.; Bach, U.; Spencer, R.; Kadler, M.; Church, M.; Balucinska-Church, M.; Wilms, J.; Hanke, M.; Zola, S.; Schulz, N.

    2009-05-01

    The neutron star X-ray binary Cygnus X-2 was observed using the e- EVN (European VLBI Network) on May 12/13th 2009 between 23:00-13:00 UT at 5 GHz. The radio telescopes participating with the e-EVN at 5 GHz were Effelsberg, Medicina, Onsala 25m, Torun, Sheshan, Yebes, Jodrell Bank MKII, Cambridge and Knockin. A maximum data rate of 1024 Mbps were achieved from four telescopes (Effelsberg, Onsala, Torun and Jodrell Bank MKII).

  20. Effect of the electric field pattern on the generation of fast electrons in front of lower hybrid launchers

    NASA Astrophysics Data System (ADS)

    Valade, Laurent; Fuchs, Vladimir; Ekedahl, Annika; Petrzilka, Vaclav; Colas, Laurent; Goniche, Marc; Hillairet, Julien; Li, Miaohui; Zhang, Bin

    2015-12-01

    The effect of the detailed waveguide spectrum on the electron acceleration has been studied for the 3.7 GHz LHCD launchers in Tore Supra, i.e. the ITER-like passive-active multijunction (PAM) launcher and the fully-active-multijunction (FAM) launcher, using test electron modelling technique. The detailed launched antenna wave spectrum is used as input to the code that computes the dynamics of the electrons in the electric field. Comparison with the LHCD launchers in EAST, operating at 2.45 GHz and 4.6 GHz, has also been made. The simulations show that the PAM-design generates lower flux of fast electrons than FAM-launchers, this could be the consequence of the wider waveguide of PAM-launcher (14.65 mm for Tore-Supra) than FAM-launcher (8 mm for Tore-Supra).

  1. Effect of the electric field pattern on the generation of fast electrons in front of lower hybrid launchers

    SciTech Connect

    Valade, Laurent Ekedahl, Annika; Colas, Laurent; Goniche, Marc; Hillairet, Julien; Fuchs, Vladimir; Petrzilka, Vaclav; Li, Miaohui; Zhang, Bin

    2015-12-10

    The effect of the detailed waveguide spectrum on the electron acceleration has been studied for the 3.7 GHz LHCD launchers in Tore Supra, i.e. the ITER-like passive-active multijunction (PAM) launcher and the fully-active-multijunction (FAM) launcher, using test electron modelling technique. The detailed launched antenna wave spectrum is used as input to the code that computes the dynamics of the electrons in the electric field. Comparison with the LHCD launchers in EAST, operating at 2.45 GHz and 4.6 GHz, has also been made. The simulations show that the PAM-design generates lower flux of fast electrons than FAM-launchers, this could be the consequence of the wider waveguide of PAM-launcher (14.65 mm for Tore-Supra) than FAM-launcher (8 mm for Tore-Supra)

  2. Toroidal Rotation in RF Heated JET Plasmas

    SciTech Connect

    Eriksson, L.-G.; Nave, F.; Zastrow, K.-D.

    2007-09-28

    Experiments have been carried out on JET aimed at studying rotation in RF heated plasmas with low external momentum input. Both plasmas with Ion Cyclotron Resonance Frequency (ICRF) heating and Lower Hybrid Current Drive (LHCD) have been investigated. The rotation profiles are measured by Charge Exchange recombination spectroscopy, using short diagnostic Neutral Beam Injection (NBI) pulses. Moreover, the temporal evolution of the central rotation could in some cases be deduced from MHD activity. While most of the measurements were focussed on ICRF heating, the profiles measured in plasmas with LHCD are interesting since they are the first reported from JET in such plasmas. In particular, they allowed for studies of rotation in RF heated plasmas with q>1. The experimental results are presented together with an analysis of the torque from ICRF heated fast ions.

  3. Overview of Alcator C-Mod Contribution to the 2015 JRT on Off Axis Current Drive

    NASA Astrophysics Data System (ADS)

    Wallace, G. M.; Bonoli, P. T.; Faust, I. C.; Mumgaard, R. T.; Parker, R. R.; Rice, J. E.; Shirawia, S.; Scott, S. D.; Bhattacharjee, A.; Ebrahimi, F.; Poli, F.; Gerhardt, S.; Podesta, M.; Solomon, W.; Wilson, J. R.; Holcomb, C.

    2015-11-01

    The goal of the US Department of Energy FES 2015 Joint Research Target (JRT) is to conduct experiments and analysis to quantify the impact of broadened current and pressure profiles on tokamak plasma confinement and stability. Broadened current profiles are achieved on Alcator C-Mod through the use of Lower Hybrid Current Drive (LHCD). C-Mod experiments from the recent run campaign have focused on several areas, such as MHD stability of discharges with broad current profiles, energy transport barriers and high-Z impurity transport in non-inductive discharges, momentum transport in discharges with altered safety factor profiles, and validation of LHCD actuator models. This work was conducted on the Alcator C-Mod tokamak, a DoE Office of Science user facility supported by US Department of Energy cooperative agreement DE-FC02-99ER54512.

  4. Optimization of Lower Hybrid Current Drive Efficiency for EAST Plasma with Non-Circular Cross Section and Finite Aspect-Ratio

    NASA Astrophysics Data System (ADS)

    Shi, Xingjian; Hu, Yemin; Gao, Zhe

    2012-03-01

    The two-dimensional equilibrium with flexible boundaries is solved via using a MAT-LAB Equilibrium Code (MEC), which has applied the finite element method to handle the changeable plasma shape and employed the trust-region dogleg method to solve the nonlinear partial differential equation. The corresponding driven current profile is also calculated by coupling with the lower-hybrid simulation code (LSC). The results are applied to optimize the lower hybrid current drive (LHCD) efficiency for the Experimental Advanced Superconductor Tokamak (EAST) and suggested that both elongation and triangularity have a notable effect on the efficiency because of the competition between the increase in the resonant area and in the Shafranov shift. Moreover, large aspect-ratio has a negative effect on the efficiency. These effects are studied numerically, which might be considered carefully for both good plasma confinement and high LHCD efficiency.

  5. Improved Controls for Fusion RF Systems. Final technical report

    SciTech Connect

    Casey, Jeffrey A.

    2011-11-08

    We have addressed the specific requirements for the integrated systems controlling an array of klystrons used for Lower Hybrid Current Drive (LHCD). The immediate goal for our design was to modernize the transmitter protection system (TPS) for LHCD on the Alcator C-Mod tokamak at the MIT Plasma Science and Fusion Center (MIT-PSFC). Working with the Alcator C-Mod team, we have upgraded the design of these controls to retrofit for improvements in performance and safety, as well as to facilitate the upcoming expansion from 12 to 16 klystrons. The longer range goals to generalize the designs in such a way that they will be of benefit to other programs within the international fusion effort was met by designing a system which was flexible enough to address all the MIT system requirements, and modular enough to adapt to a large variety of other requirements with minimal reconfiguration.

  6. Lower hybrid current drive at ITER-relevant high plasma densities

    SciTech Connect

    Cesario, R.; Amicucci, L.; Cardinali, A.; Castaldo, C.; Marinucci, M.; Panaccione, L.; Pericoli-Ridolfini, V.; Tuccillo, A. A.; Tudisco, O.

    2009-11-26

    Recent experiments indicated that a further non-inductive current, besides bootstrap, should be necessary for developing advanced scenario for ITER. The lower hybrid current drive (LHCD) should provide such tool, but its effectiveness was still not proved in operations with ITER-relevant density of the plasma column periphery. Progress of the LH deposition modelling is presented, performed considering the wave physics of the edge, and different ITER-relevant edge parameters. Operations with relatively high edge electron temperatures are expected to reduce the LH{sub ||} spectral broadening and, consequently, enabling the LH power to propagate also in high density plasmas ({sub ||} is the wavenumber component aligned to the confinement magnetic field). New results of FTU experiments are presented, performed by following the aforementioned modeling: they indicate that, for the first time, the LHCD conditions are established by operating at ITER-relevant high edge densities.

  7. Lower Hybrid Heating and Current Drive on the Alcator C-Mod Tokamak

    SciTech Connect

    R. Wilson, R. Parker, M. Bitter, P.T. Bonoli, C. Fiore, R.W. Harvey, K. Hill, A.E. Hubbard, J.W. Hughes, A. Ince-Cushman, C. Kessel, J.S. Ko, O. Meneghini, C.K. Phillips, M. Porkolab, J. Rice, A.E. Schmidt, S. Scott,S. Shiraiwa, E. Valeo, G.Wallace, J.C. Wright and the Alcator C-Mod Team

    2009-11-20

    On the Alcator C-Mod tokamak, lower hybrid current drive (LHCD) is being used to modify the current profile with the aim of obtaining advanced tokamak (AT) performance in plasmas with parameters similar to those that would be required on ITER. To date, power levels in excess of 1 MW at a frequency of 4.6 GHz have been coupled into a variety of plasmas. Experiments have established that LHCD on C-Mod behaves globally as predicted by theory. Bulk current drive efficiencies, n20IlhR/Plh ~ 0.25, inferred from magnetics and MSE are in line with theory. Quantitative comparisons between local measurements, MSE, ECE and hard x-ray bremsstrahlung, and theory/simulation using the GENRAY, TORIC-LH CQL3D and TSC-LSC codes have been performed. These comparisons have demonstrated the off-axis localization of the current drive, its magnitude and location dependence on the launched n|| spectrum, and the use of LHCD during the current ramp to save volt-seconds and delay the peaking of the current profile. Broadening of the x-ray emission profile during ICRF heating indicates that the current drive location can be controlled by the electron temperature, as expected. In addition, an alteration in the plasma toroidal rotation profile during LHCD has been observed with a significant rotation in the counter current direction. Notably, the rotation is accompanied by peaking of the density and temperature profiles on a current diffusion time scale inside of the half radius where the LH absorption is taking place.

  8. Investigations of LHW-plasma coupling and current drive at high density related to H-mode experiments in EAST

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Li, Y. C.; Zhang, L.; Li, M. H.; Wei, W.; Kong, E. H.; Wang, M.; Xu, H. D.; Wang, S. L.; Xu, G. S.; Zhao, L. M.; Hu, H. C.; Jia, H.; Cheng, M.; Yang, Y.; Liu, L.; Zhao, H. L.; Peysson, Y.; Decker, J.; Goniche, M.; Amicucci, L.; Cesario, R.; Tuccillo, A. A.; Baek, S. G.; Parker, R.; Bonoli, P. T.; Paoletti, F.; Yang, C.; Shan, J. F.; Liu, F. K.; Zhao, Y. P.; Gong, X. Z.; Hu, L. Q.; Gao, X.; Wan, B. N.; Li, J. G.; the EAST Team

    2015-09-01

    Two important issues in achieving lower hybrid current drive (LHCD) high confinement plasma in EAST are to improve lower hybrid wave (LHW)-plasma coupling and to drive the plasma current at a high density. Studies in different configurations with different directions of toroidal magnetic field (Bt) show that the density near the antenna is affected by both the radial electric field induced by plasma without a LHW (Er_plasma) in the scrape off layer (SOL), and the radial electric field induced by LHW power (Er_LH) near the grill. Investigations indicate that Er  ×  Bt in the SOL leads to a different effect of configuration on the LHW-plasma coupling and Er_LH  ×  Bt accounts for the asymmetric density behaviour in the SOL observed in the experiments, where Er is the total radial electric field in the SOL. Modelling of parametric instability (PI), collisional absorption (CA) and scattering from density fluctuations (SDF) in the edge region, performed considering the parameters of high density LHCD experiments in EAST, has shown that these mechanisms could be responsible for the low current drive (CD) efficiency at high density. Radiofrequency probe spectra, useful for documenting PI occurrence, show sidebands whose amplitude in the case of the lithiated vacuum chamber is smaller than in the case of poor lithiation, consistently with growth rates from PI modeling of the respective reference discharges. Since strong lithiation is also expected to diminish the parasitic effect on the LHCD of the remaining possible mechanisms, this appears to be a useful method for improving LHCD efficiency at a high density.

  9. Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas

    SciTech Connect

    Lu, Z. X.; Wang, W. X.; Diamond, P. H.; Tynan, G.; Ethier, S.; Gao, C.; Rice, J.

    2015-05-04

    We report that intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. Here we focus on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (sˆ) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak sˆ . Based on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak sˆ discharges and that the value of sˆ crit is consistent with the experimental results sˆ expcrit [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. In conclusion, the consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive sˆ .

  10. Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmas

    SciTech Connect

    Lu, Z. X.; Tynan, G.; Wang, W. X.; Ethier, S.; Diamond, P. H.; Gao, C.; Rice, J.

    2015-05-15

    Intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. This work focuses on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (s{sup ^}) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak s{sup ^}. Based on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak s{sup ^} discharges and that the value of s{sup ^}{sub crit} is consistent with the experimental results s{sup ^}{sub crit}{sup exp}≈0.2∼0.3 [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. The consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak s{sup ^} and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive s{sup ^}.

  11. Lower hybrid current drive favoured by electron cyclotron radiofrequency heating

    SciTech Connect

    Cesario, R.; Cardinali, A.; Castaldo, C.; Marinucci, M.; Tuccillo, A. A.; Giruzzi, G.; Napoli, F.; Schettini, G.

    2014-02-12

    The important goal of adding to the bootstrap a fraction of non-inductive plasma current, which would be controlled for obtaining and optimizing steady-state profiles, can be reached by using the Current Drive produced by Lower Hybrid waves (LHCD). FTU (Frascati Tokamak Upgrade) experiments demonstrated, indeed, that LHCD is effective at reactor-graded high plasma density, and the LH spectral broadening is reduced, operating with higher electron temperature in the outer region of plasma column (T{sub e-periphery}). This method was obtained following the guidelines of theoretical predictions indicating that the broadening of launched spectrum produced by parametric instability (PI) should be reduced, and the LHCD effect at high density consequently enabled, under higher (T{sub e-periphery}). In FTU, the temperature increase in the outer plasma region was obtained by operating with reduced particle recycling, lithized walls and deep gas fuelling by means of fast pellet. Heating plasma periphery with electron cyclotron resonant waves (ECRH) will provide a further tool for achieving steady-state operations. New FTU experimental results are presented here, demonstrating that temperature effect at the plasma periphery, affecting LH penetration, occurs in a range of plasma parameters broader than in previous work. New information is also shown on the modelling assessing frequencies and growth rates of the PI coupled modes responsible of spectral broadening. Finally, we present the design of an experiment scheduled on FTU next campaign, where ECRH power is used to slightly increase the electron temperature in the outer plasma region of a high-density discharge aiming at restoring LHCD. Consequent to model results, by operating with a toroidal magnetic field of 6.3 T, useful for locating the electron cyclotron resonant layer at the periphery of the plasma column (r/a∼0.8, f{sub 0}=144 GHz), an increase of T{sub e} in the outer plasma (from 40 eV to 80 eV at r/a∼0.8) is

  12. VizieR Online Data Catalog: First Caltech-Jodrell Bank VLBI Survey. III (Xu+ 1995)

    NASA Astrophysics Data System (ADS)

    Xu, W.; Readhead, A. C. S.; Pearson, T. J.; Polatidis, A. G.; Wilkinson, P. N.

    1996-02-01

    We present the 5GHz results from the first Caltech-Jodrell Bank (CJ1) VLBI survey. The 1.6GHz maps were presented in two separate papers, Polatidis et al. and Thakkar et al. . These three papers complete the first stage of this program to map at both 1.6 and 5GHz all objects accessible to Mark II VLBI in the complete sample of 135 objects with 1.3>S(5Ghz)>=0.7Jy, Dec(1950)>=35deg, and |b|>10deg. The combination of the CJ1 sample with the Pearson-Readhead (PR) sample provides a complete, flux density-limited sample of 200 objects with S(5GHz)>=0.7Jy, Dec(1950)>=35deg, |b|>10deg for which all of the objects accessible to Mark II VLBI have been mapped at both 5GHz (129 objects) and 1.6GHz (132 objects). In addition to the 5GHz VLBI maps, we present in this paper 5GHz MERLIN observations of 20 objects and 1.4GHz VLA observations of 92 objects in the combined CJ1 + PR sample. The VLA maps, together with L-band (1.3-1.7GHz) maps available in the literature, provide a complete set of VLA maps for the combined CJ1 + PR sample. Finally, we present the radio spectra of the objects in the CJ1 sample. The combined CJ1 + PR VLBI surveys provide a sample which is large enough for a number of important astrophysical and cosmological studies. These will be presented in further papers in this series. (4 data files).

  13. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Lee, W.; Park, H. K.; Lee, D. J.; Nam, Y. U.; Leem, J.; Kim, T. K.

    2016-04-01

    The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm-1. The upper limit corresponds to the normalized wavenumber kθρe of ˜0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.

  14. Statistical analysis of temporal and spatial evolution of in-vessel dust particles in fusion devices by using CCD images

    NASA Astrophysics Data System (ADS)

    Hong, Suk-Ho; Kim, Kyung-Rae; Nam, Yong-Un; Chung, Jinil; Grisolia, Christian; Rohde, Volker; KSTAR Team; TORE SUPRA Team; ASDEX Upgrade Team

    2013-08-01

    Images of wide-angle visible standard CCD cameras contain information on Dust Creation Events (DCEs) that occur during plasma operations. Database on the DCEs can be built by analyzing the straight line-like dust trajectories in scrape-off layer caused by plasma-dust interaction along the vacuum vessel. The database provides short/long term temporal evolution and spatial distribution of origins of DCEs in fusion devices. We have studied DCEs of 2011 KSTAR campaign and compared with that of 2006 Tore Supra (TS) and 2007 ASDEX Upgrade (AUG) campaign. An analysis software, with which the location of dust trajectories in 3D position in the KSTAR vacuum vessel is identified, is developed and the dust velocity distribution in 2011 campaign is measured. ©2001 Elsevier Science.

  15. High contrast 2D visualization of edge plasma instabilities by ECE imaging

    NASA Astrophysics Data System (ADS)

    Yun, G. S.; Choi, M. J.; Lee, W.; Park, H. K.; Domier, C. W.; Luhmann, N. C., Jr.

    2012-01-01

    High contrast high resolution 2D images of edge MHD instabilities have been obtained for the KSTAR H-mode plasmas in 2010 using an electron cyclotron emission (ECE) imaging system. A fast structural evolution of the edge instabilities has been identified where the validity of the observed structures, i.e., the local measurement is ensured by the high contrast. On the other hand, the exact interpretation of the ECE intensity (Trad) is not straightforward due to the marginal optical depth ( ~ 1) in the plasma edge region. The effect of the electron temperature (Te) and density (ne) profiles in the edge region on the ECE localization and intensity have been evaluated for typical KSTAR H-mode discharges.

  16. Conceptual design of new polychromator on Thomson scattering system to measure Z{sub eff}

    SciTech Connect

    Lee, Jongha; Oh, Seungtae; Wi, Hanmin; Oh, Youngkook; Yamada, I.; Narihara, K.; Kawahata, K.; Jeon, Jongsu

    2012-10-15

    To measure the Z{sub eff} with electron temperature (T{sub e}) and electron density (n{sub e}) profiles at the same time and the same position in the KSTAR tokamak, we design a new polychromator for Thomson scattering system that has additional function. The additional function is measuring bremsstrahlung intensity to calculate Z{sub eff} independent of Thomson signals. For this new polychromator, we design and fabricate a collimation lens set, and interference filter that has center wavelength of 523 nm and 2 nm FWHM. Finally, we change the lenses, detector diodes, and add the bremsstrahlung filter on the KSTAR edge Thomson scattering polychromator. Then this new polychromator was tested by Tungsten light and monochromator.

  17. Cross Sections for the $\\gamma p \\to K^{*0}\\Sigma^+$ Reaction at $E_\\gamma = 1.7 - 3.0$ GeV

    SciTech Connect

    I. Hleiqawi; K. Hicks; D.Carman; T.Mibe

    2007-04-01

    Differential cross sections for the reaction $\\gamma p \\to K^{*0} \\Sigma^+$ are presented at nine bins in photon energy in the range from 1.7 to 3.0 GeV. The \\kstar was detected by its decay products, $K^+\\pi^-$, in the CLAS detector at Jefferson Lab. These data are the first \\kstar photoproduction cross sections ever published over a broad range of angles. Comparison with a theoretical model based on the vector and tensor $K^*$-quark couplings shows good agreement with the data in general, after adjusting the model's two parameters in a fit to our data. Disagreement between the data at forward angles and the global angle-energy fit to the model suggests that the role of scalar $\\kappa$ meson exchange in $t$-channel diagrams should be investigated.

  18. Design of a collective scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research.

    PubMed

    Lee, W; Park, H K; Lee, D J; Nam, Y U; Leem, J; Kim, T K

    2016-04-01

    The design characteristics of a multi-channel collective (or coherent) scattering system for small scale turbulence study in Korea Superconducting Tokamak Advanced Research (KSTAR), which is planned to be installed in 2017, are given in this paper. A few critical issues are discussed in depth such as the Faraday and Cotton-Mouton effects on the beam polarization, radial spatial resolution, probe beam frequency, polarization, and power. A proper and feasible optics with the 300 GHz probe beam, which was designed based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wavenumbers up to 24 cm(-1). The upper limit corresponds to the normalized wavenumber kθρe of ∼0.15 in nominal KSTAR plasmas. To detect the scattered beam power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed.

  19. Spatial heterodyne Stokes vector imaging of the motional Stark-Zeeman multiplet.

    PubMed

    Howard, John; Chung, Jinil

    2012-10-01

    We present a general Stokes interferometer/polarimeter suitable for polarimetric imaging the elliptically polarized motional Stark-Zeeman multiplet. We also introduce a fully phase-heterodyne spatial multiplex variant of the system that has been used for imaging of Balmer alpha emission from the heating neutral beam in the KSTAR super-conducting tokamak in Korea. The polarimeter performance is illustrated using various polarization test targets. PMID:23126853

  20. Simulation of tokamak SOL and divertor region including heat flux mitigation by gas puffing

    SciTech Connect

    Park, Jin Woo; Na, Y. S.; Hong, S. H.; Ahn, J.W.; Kim, D. K.; Han, Hyunsun; Shim, Seong Bo; Lee, Hae June

    2012-01-01

    Two-dimensional (2D), scrape-off layer (SOL)-divertor transport simulations are performed using the integrated plasma-neutral-impurity code KTRAN developed at Seoul National University. Firstly, the code is applied to reproduce a National Spherical Torus eXperiment (NSTX) discharge by using the prescribed transport coefficients and the boundary conditions obtained from the experiment. The plasma density, the heat flux on the divertor plate, and the D (alpha) emission rate profiles from the numerical simulation are found to follow experimental trends qualitatively. Secondly, predictive simulations are carried out for the baseline operation mode in Korea Superconducting Tokamak Advanced Research (KSTAR) to predict the heat flux on the divertor target plates. The stationary peak heat flux in the KSTAR baseline operation mode is expected to be 6.5 MW/m(2) in the case of an orthogonal divertor. To study the mitigation of the heat flux, we investigated the puffing effects of deuterium and argon gases. The puffing position is assumed to be in front of the strike point at the outer lower divertor plate. In the simulations, mitigation of the peak heat flux at the divertor target plates is found to occur when the gas puffing rate exceeds certain values, similar to 1.0 x 10(20) /s and similar to 5.0 x 10(18) /s for deuterium and argon, respectively. Multi-charged impurity transport is also investigated for both NSTX and KSTAR SOL and divertor regions.

  1. Resolving the uncertainties of non-axisymmetric fields in tokamaks

    NASA Astrophysics Data System (ADS)

    in, Yongkyoon; Seol, J.; Ko, W. H.; Lee, S. G.; Yoon, S. W.; Lee, H. H.; Jeon, Y. M.; Kim, J.; Bak, J. G.; Park, H.; Park, J. K.; Yun, G. S.; 3D Physics Task Force Team

    2015-11-01

    Recent study suggests that KSTAR could be a benefactor of the extremely low level of intrinsic error field in n =1 resonant magnetic perturbation (RMP) driven edge localized modes (ELM) control. Specifically, when the n = 1 RMP currents increases in order to suppress/mitigate ELMs, a kink-resonant mode-locking is not usually invoked in KSTAR, unlike in other devices. Besides we have discovered that the mid-plane RMP appeared much more effective than the off-midplane RMPs in affecting the ELMs with strong density pump-outs and enhanced ELM frequency. Presently, the enhanced understanding of non-axisymmetric field in tokamaks has been in great need, in particular, for the ITER RMP requirements. As the prevailing design of in-vessel RMP coils in ITER is similar to that in KSTAR, we are keen to resolve the uncertainties of the non-axisymmetric fields on transport and stability, and their limits, contributing directly to ITER and beyond.

  2. Charge exchange spectroscopy system calibration for ion temperature measurement in KSTARa)

    NASA Astrophysics Data System (ADS)

    Ko, Won-Ha; Lee, Hyungho; Seo, Dongcheol; Kwon, Myeun

    2010-10-01

    The charge exchange spectroscopy (CES) system including collection assemblies, lens design, and cassettes for the KSTAR experiment was installed to obtain profiles of the ion temperature and the toroidal rotation velocity from charge exchange emission between plasma ions and beam neutrals near the plasma axis by using a modulated neutral beam and a background system. We can measure the charge exchange spectra of an impurity line such as the 529 nm line of carbon VI to get ion temperature and rotation profiles in KSTAR. The CES and background systems will have absolute intensity and spectral calibrations using a calibrated source and various spectral lamps. The calibration was done inside the tokamak after all CES systems are installed and the optical systems are slid into the cassettes. This requires that the diagnostic systems are installed near the vacuum vessel inside the cryostat maintaining the superconducting state of the superconducting coils. Repeated spectral calibrations of the spectrometer and charge coupled device for CES will be made in the diagnostic room during the experimental campaign. We show a detailed description of the KSTAR CES system, how to calibrate, and the results of calibration.

  3. Simulation of tokamak SOL and divertor region including heat flux mitigation by gas puffing

    NASA Astrophysics Data System (ADS)

    Park, Jin-Woo; Na, Yong-Su; Hong, Sang Hee; Ahn, Joon-Wook; Kim, Deok-Kyu; Han, Hyunsun; Shim, Seong Bo; Lee, Hae June

    2012-08-01

    Two-dimensional (2D), scrape-off layer (SOL)-divertor transport simulations are performed using the integrated plasma-neutral-impurity code KTRAN developed at Seoul National University. Firstly, the code is applied to reproduce a National Spherical Torus eXperiment (NSTX) discharge by using the prescribed transport coefficients and the boundary conditions obtained from the experiment. The plasma density, the heat flux on the divertor plate, and the D α emission rate profiles from the numerical simulation are found to follow experimental trends qualitatively. Secondly, predictive simulations are carried out for the baseline operation mode in Korea Superconducting Tokamak Advanced Research (KSTAR) to predict the heat flux on the divertor target plates. The stationary peak heat flux in the KSTAR baseline operation mode is expected to be 6.5 MW/m2 in the case of an orthogonal divertor. To study the mitigation of the heat flux, we investigated the puffing effects of deuterium and argon gases. The puffing position is assumed to be in front of the strike point at the outer lower divertor plate. In the simulations, mitigation of the peak heat flux at the divertor target plates is found to occur when the gas puffing rate exceeds certain values, ˜1.0 × 1020 /s and ˜5.0 × 1018 /s for deuterium and argon, respectively. Multi-charged impurity transport is also investigated for both NSTX and KSTAR SOL and divertor regions.

  4. Effects of neoclassical toroidal viscosity induced by the intrinsic error fields and toroidal field ripple on the toroidal rotation in tokamaks

    NASA Astrophysics Data System (ADS)

    Lee, H. H.; Seol, J.; Ko, W. H.; Terzolo, L.; Aydemir, A. Y.; In, Y.; Ghim, Y.-c.; Lee, S. G.

    2016-08-01

    Effects of neoclassical toroidal viscosity (NTV) induced by intrinsic error fields and toroidal field ripple on cocurrent toroidal rotation in H-mode tokamak plasmas are investigated. It is expected that large NTV torque can be localized at the edge region through the 1/ν-regime in the vicinity of E r ˜ 0 in the cocurrent rotating H-mode plasma. Numerical simulation on toroidal rotation demonstrates that the edge localized NTV torque determined by the intrinsic error fields and toroidal field ripples in the level of most tokamaks can damp the toroidal rotation velocity over the whole region while reducing the toroidal rotation pedestal which is clearly observed in Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. It is found that the NTV torque changes the toroidal rotation gradient in the pedestal region dramatically, but the toroidal rotation profile in the core region responds rigidly without a change in the gradient. On the other hand, it shows that the NTV torque induced by the intrinsic error fields and toroidal field ripple in the level of the KSTAR tokamak, which are expected to be smaller than most tokamaks by at least one order of magnitude, is negligible in determining the toroidal rotation velocity profile. Experimental observation on the toroidal rotation change by the externally applied nonaxisymmetric magnetic fields on KSTAR also suggests that NTV torque arising from nonaxisymmetric magnetic fields can damp the toroidal rotation over the whole region while diminishing the toroidal rotation pedestal.

  5. Tri-band small monopole antenna based on SRR units

    NASA Astrophysics Data System (ADS)

    Shehata, Gehan; Mohanna, Mahmoud; Rabeh, Mohammed Lotfy

    2015-12-01

    In this paper a novel design for a tri-band monopole antenna coupled with metamaterial units is introduced. The proposed antenna was designed to cover WiMAX (2.5, 3.5) and WLAN (5.2) bands. In our proposal, a coplanar waveguide (CPW) fed circular-disk monopole antenna is coupled with three split ring resonator (SRR) units which exist on its back side. In our design a monopole antenna and SRR units are designed first to resonate at 5.2 GHz and 2.5 GHz respectively. In addition, antenna is loaded with post to force resonance at 3.5 GHz. SRR units are used for 2.5 GHz resonance to miniaturize antenna size, and our proposed antenna considered an electrically small antenna (ESA) at its first resonance frequency. Simulated and measured results exhibit a good agreement that validate our design.

  6. Application of carbon nanomaterial as a microwave absorber.

    PubMed

    Sharon, Maheshwar; Pradhan, Debabrata; Zacharia, Renju; Puri, Vijaya

    2005-12-01

    Microwave absorption (8 GHz to 12 GHz) studies have been made with carbon nanomaterials for the first time. Carbon nanomaterials are synthesized by the pyrolysis of camphor. It is observed that film of carbon prepared under certain synthetic condition, can absorb microwave of either some specific wavelengths e.g., 9.5 GHz and 11.5 GHz or full range from 8-12 GHz to the extent of 20 dB depending upon their preparation condition. Carbon nanobeads seems to absorb the microwave in the range of 8-12 GHz.

  7. Designing A Mode Converter For Use With A Gyrotron

    NASA Technical Reports Server (NTRS)

    Hoppe, Daniel J.

    1995-01-01

    Report describes process of designing corrugated, circular-cross-section length of waveguide converting input electromagnetic radiation at frequency of 34.5 GHz in TM(11) mode to output radiation in HE(11) mode. TM(11)-mode input radiation supplied by gyrotron generating continuous-wave power of 200 kW at 34.5 GHz in TE(01) mode followed by TE(01)-to-TM(11) mode converter. Together, gyrotron and mode converters constitute prototype high-power transmitter for long-distance free-space communication.

  8. Suspended substrate stripline filters for ESM applications

    NASA Astrophysics Data System (ADS)

    Dean, J. E.

    1985-07-01

    Multi-octave contiguous channel multiplexers are a key component in EW systems, since they provide the front-end signal sorting. The paper describes advances in the development of broadband, low-loss, selective, lowpass, highpass and bandpass filters and contiguous channel multiplexers from 500 MHz to 26.5 GHz, in the form of suspended substrate stripline (SSS) realizations, in particular to increased bandwidth/channel and increased band-edge selectivity. The paper also discusses a novel range of low-loss, selective, broadband filters, recently designed using lumped-element technology to provide a high performance over 20 MHz to 1.5 GHz.

  9. The 40 and 50 GHz propagation experiments at the Rutherford Appleton Laboratory, UK, using the ITALSAT beacons

    NASA Technical Reports Server (NTRS)

    Woodroffe, J. M.; Davies, P. G.; Ladd, D. N.; Norbury, John R.

    1994-01-01

    This paper describes the current experimental program and future plans for the reception of transmissions from the 18.7, 39.6, and 49.5 GHz beacons from the ITALSAT satellite by the Radio Communications Research Unit at Rutherford Appleton Laboratory, UK. The Radio Communications Research Unit, which has had considerable experience in developing experimental millimetric equipment for propagation studies, has initiated the development of a single-channel receiver and a triple-channel receiver to measure propagation effects at 49.5 GHz and 39.6 GHz respectively. The initial location of the receivers will be at Chilbolton, Hampshire, UK.

  10. Photonic approach for microwave frequency measurement with adjustable measurement range and resolution using birefringence effect in highly non-linear fiber.

    PubMed

    Feng, Danqi; Xie, Heng; Qian, Lifen; Bai, Qinhong; Sun, Junqiang

    2015-06-29

    We experimentally demonstrate a novel approach for microwave frequency measurement utilizing birefringence effect in the highly non-linear fiber (HNLF). A detailed theoretical analysis is presented to implement the adjustable measurement range and resolution. By stimulating a complementary polarization-domain interferometer pair in the HNLF, a mathematical expression that relates the microwave frequency and amplitude comparison function is developed. We carry out a proof-to-concept experiment. A frequency measurement range of 2.5-30 GHz with a measurement error within 0.5 GHz is achieved except 16-17.5 GHz. This method is all-optical and requires no high-speed electronic components. PMID:26191769

  11. A fully integrated low-noise amplifier in SiGe 0.35 μm technology for 802.11a WIFI applications

    NASA Astrophysics Data System (ADS)

    Pulido, R.; Khemchandani, S. L.; Goni-Iturri, A.; Diaz, R.; Hernandez, A.; del Pino, J.

    2005-06-01

    In the last years, WIFI market has shown an incredible growth, exceeding expectations. This paper presents the design of two fully integrated LNAs using a low cost SiGe 0.35 um technology for the 5 GHz band, according to the IEEE 802.11a WIFI standard. One LNA has an asymmetric configuration and the other a balanced configuration. A comparison between the two LNAs has been made. All passives devices are on chip, including integrated inductors which have been designed by electromagnetic simulations. This work demonstrates the feasibility of a low cost silicon technology for the design of 5 GHz band circuits

  12. Characterization of the onset of ion cyclotron parametric decay instability of lower hybrid waves in a diverted tokamak

    SciTech Connect

    Baek, S. G. Parker, R. R.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Porkolab, M.; Brunner, D.; Faust, I. C.; Hubbard, A. E.; LaBombard, B.; Lau, C.; Takase, Y.

    2014-06-15

    The goal of the lower hybrid current drive (LHCD) program on Alcator C-Mod is to develop and optimize reactor-relevant steady-state plasmas by controlling current density profile. However, current drive efficiency precipitously decreases as the line averaged density (n{sup ¯}{sub e}) increases above ∼1 × 10{sup 20} m{sup −3}. Previous simulations show that the observed loss of current drive efficiency in high density plasmas stems from the interactions of LH waves with edge/scrape-off layer plasmas [Wallace et al., Phys. Plasmas 19, 062505 (2012)]. A recent observation [Baek et al., Plasma Phys. Controlled Fusion 55, 052001 (2013)] shows that the configuration dependent ion cyclotron parametric decay instability (PDI) is excited in the density range where the discrepancy between the experiments and simulations remains. Comparing the observed spectra with the homogeneous growth rate spectra indicates that the observed ion cyclotron PDI can be excited not only at the low-field-side but also at the high-field-side (HFS) edge of the tokamak. The model analysis shows that a relevant PDI process to Alcator C-Mod LHCD experiments is decay into ion cyclotron quasi-mode driven by parallel coupling. The underlying cause of the observed onset of ion cyclotron PDI is likely due to the weaker radial penetration of the LH wave in high density plasmas, which can lead to enhanced convective growth. Configuration-dependent PDIs are found to be correlated with different edge density profiles in different magnetic configurations. While the HFS edge of the tokamak can be potentially susceptible to PDI, as evidenced by experimental observations and ray-tracing analyses, enhancing single-pass absorption is expected to help recover the LHCD efficiency at reactor-relevant densities because it could suppress several parasitic loss mechanisms that are exacerbated in multi-pass regimes.

  13. Characterization of the onset of ion cyclotron parametric decay instability of lower hybrid waves in a diverted tokamak

    NASA Astrophysics Data System (ADS)

    Baek, S. G.; Parker, R. R.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Porkolab, M.; Takase, Y.; Brunner, D.; Faust, I. C.; Hubbard, A. E.; LaBombard, B.; Lau, C.

    2014-06-01

    The goal of the lower hybrid current drive (LHCD) program on Alcator C-Mod is to develop and optimize reactor-relevant steady-state plasmas by controlling current density profile. However, current drive efficiency precipitously decreases as the line averaged density (n¯e) increases above ˜1 × 1020 m-3. Previous simulations show that the observed loss of current drive efficiency in high density plasmas stems from the interactions of LH waves with edge/scrape-off layer plasmas [Wallace et al., Phys. Plasmas 19, 062505 (2012)]. A recent observation [Baek et al., Plasma Phys. Controlled Fusion 55, 052001 (2013)] shows that the configuration dependent ion cyclotron parametric decay instability (PDI) is excited in the density range where the discrepancy between the experiments and simulations remains. Comparing the observed spectra with the homogeneous growth rate spectra indicates that the observed ion cyclotron PDI can be excited not only at the low-field-side but also at the high-field-side (HFS) edge of the tokamak. The model analysis shows that a relevant PDI process to Alcator C-Mod LHCD experiments is decay into ion cyclotron quasi-mode driven by parallel coupling. The underlying cause of the observed onset of ion cyclotron PDI is likely due to the weaker radial penetration of the LH wave in high density plasmas, which can lead to enhanced convective growth. Configuration-dependent PDIs are found to be correlated with different edge density profiles in different magnetic configurations. While the HFS edge of the tokamak can be potentially susceptible to PDI, as evidenced by experimental observations and ray-tracing analyses, enhancing single-pass absorption is expected to help recover the LHCD efficiency at reactor-relevant densities because it could suppress several parasitic loss mechanisms that are exacerbated in multi-pass regimes.

  14. Conditions for Lower Hybrid Current Drive in ITER

    NASA Astrophysics Data System (ADS)

    Cesario, R.; Amicucci, L.; Cardinali, A.; Castaldo, C.; Ceccuzzi, S.; Napoli, F.; Tuccillo, A. A.; Galli, A.; Schettini, G.

    2012-12-01

    To control the plasma current profile represents one of the most important problems of the research of nuclear fusion energy based on the tokamak concept, as in the plasma column the necessary conditions of stability and confinement should be satisfied. This problem can be solved by using the lower hybrid current drive (LHCD) effect, which was demonstrated to occur also at reactor grade high plasma densities provided that a proper method should be utilised, as assessed on FTU (Frascati Tokamak Upgrade). This method, based on theoretical predictions confirmed by experiment, produces relatively high electron temperature at the plasma periphery and scrape-off layer (SOL), consequently reducing the broadening of the spectrum launched by the antenna produced by parasitic wave physics of the edge, namely parametric instability (PI). The new results presented here show that, for kinetic profiles now foreseen for the SOL of ITER, PI is expected to hugely broaden the antenna spectrum and prevent any penetration in the core of the coupled LH power. However, considering the FTU method and assuming higher electron temperature at the edge (which would be however reasonable for ITER) the PI-produced spectral broadening would be mitigated, and enable the penetration of the coupled LH power in the main plasma. By successful LHCD effect, the control of the plasma current profile at normalised minor radius of about 0.8 would be possible, with much higher efficiency than that obtainable by other tools. A very useful reinforce of bootstrap current effects would be thus possible by LHCD in ITER.

  15. Modification of Current Profile, Toroidal Rotation and Pedestal by Lower Hybrid Waves in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Parker, R.; Bonoli, P. T.; Meneghini, O.; Porkolab, M.; Schmidt, A. E.; Shiraiwa, S.; Wallace, G.; Wilson, J. R.; Hubbard, A. E.; Hughes, J. W.; Ko, J.-S.; McDermott, R. M.; Reinke, M. L.; Rice, J. E.; Scott, S.

    2009-11-01

    Recent results from the lower hybrid current drive experiments on Alcator C-Mod are presented. These include i) MSE measurements of broadened LHCD current profiles; ii) development of counter rotation comparable to the rate of injected wave momentum; iii) modification of pedestals and rotation in H-mode; and iv) development of a new FEM-based code that models LH wave propagation from the RF source to absorption in the plasma. An improved antenna concept that will be used in the upcoming C-Mod campaigns is also briefly described.

  16. A camera for imaging hard x-rays from suprathermal electrons during lower hybrid current drive on PBX-M

    SciTech Connect

    von Goeler, S.; Kaita, R.; Bernabei, S.; Davis, W.; Fishman, H.; Gettelfinger, G.; Ignat, D.; Roney, P.; Stevens, J.; Stodiek, W. . Plasma Physics Lab.); Jones, S.; Paoletti, F. . Plasma Fusion Center); Petravich, G. . Central Research Inst. for Physics); Rimini,

    1993-05-01

    During lower hybrid current drive (LHCD), suprathermal electrons are generated that emit hard X-ray bremsstrahlung. A pinhole camera has been installed on the PBX-M tokamak that records 128 [times] 128 pixel images of the bremsstrahlung with a 3 ms time resolution. This camera has identified hollow radiation profiles on PBX-M, indicating off-axis current drive. The detector is a 9in. dia. intensifier. A detailed account of the construction of the Hard X-ray Camera, its operation, and its performance is given.

  17. A camera for imaging hard x-rays from suprathermal electrons during lower hybrid current drive on PBX-M

    SciTech Connect

    von Goeler, S.; Kaita, R.; Bernabei, S.; Davis, W.; Fishman, H.; Gettelfinger, G.; Ignat, D.; Roney, P.; Stevens, J.; Stodiek, W.; Jones, S.; Paoletti, F.; Petravich, G.; Rimini, F.

    1993-05-01

    During lower hybrid current drive (LHCD), suprathermal electrons are generated that emit hard X-ray bremsstrahlung. A pinhole camera has been installed on the PBX-M tokamak that records 128 {times} 128 pixel images of the bremsstrahlung with a 3 ms time resolution. This camera has identified hollow radiation profiles on PBX-M, indicating off-axis current drive. The detector is a 9in. dia. intensifier. A detailed account of the construction of the Hard X-ray Camera, its operation, and its performance is given.

  18. 47 CFR 97.303 - Frequency sharing requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 CFR 2.104, 2.105, and 2.106. The United States, Puerto Rico, and the U.S. Virgin Islands are in... to radio astronomy stations: 3.332-3.339 GHz, 3.3458-3.3525 GHz, 76-77.5 GHz, 78-81 GHz, 136-141...

  19. 47 CFR 97.303 - Frequency sharing requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 CFR 2.104, 2.105, and 2.106. The United States, Puerto Rico, and the U.S. Virgin Islands are in... to radio astronomy stations: 3.332-3.339 GHz, 3.3458-3.3525 GHz, 76-77.5 GHz, 78-81 GHz, 136-141...

  20. 47 CFR 97.303 - Frequency sharing requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 CFR 2.104, 2.105, and 2.106. The United States, Puerto Rico, and the U.S. Virgin Islands are in... to radio astronomy stations: 3.332-3.339 GHz, 3.3458-3.3525 GHz, 76-77.5 GHz, 78-81 GHz, 136-141...

  1. 47 CFR 25.226 - Blanket licensing provisions for domestic, U.S. Vehicle-Mounted Earth Stations (VMESs) receiving...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... GHz (Earth-to-space) frequency band, operating with Geostationary Satellites in the Fixed-Satellite... CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25.226 Blanket licensing provisions for... the 14.0-14.5 GHz (Earth-to-space) frequency band, operating with Geostationary Satellites in...

  2. 47 CFR 25.146 - Licensing and operating rules for the non-geostationary satellite orbit Fixed-Satellite Service...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...-geostationary satellite orbit Fixed-Satellite Service (NGSO FSS) in the 10.7 GHz-14.5 GHz bands. 25.146 Section... SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.146 Licensing and operating rules for the non-geostationary satellite orbit Fixed-Satellite Service (NGSO FSS) in the 10.7 GHz-14.5...

  3. 78 FR 16827 - Commercial Operations in the 3550-3650 MHz Band

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-19

    ... the NPRM, the Wireless Telecommunications Bureau and Office of Engineering and Technology announced... workshop will focus on small cell technology ``in the context of the 3.5 GHz Band as well as database and... From the Federal Register Online via the Government Publishing Office FEDERAL...

  4. 47 CFR 97.303 - Frequency sharing requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 CFR 2.104, 2.105, and 2.106. The United States, Puerto Rico, and the U.S. Virgin Islands are in... to radio astronomy stations: 3.332-3.339 GHz, 3.3458-3.3525 GHz, 76-77.5 GHz, 78-81 GHz, 136-141...

  5. 47 CFR 97.303 - Frequency sharing requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 CFR 2.104, 2.105, and 2.106. The United States, Puerto Rico, and the U.S. Virgin Islands are in... to radio astronomy stations: 3.332-3.339 GHz, 3.3458-3.3525 GHz, 76-77.5 GHz, 78-81 GHz, 136-141...

  6. 47 CFR 25.226 - Blanket licensing provisions for domestic, U.S. Vehicle-Mounted Earth Stations (VMESs) receiving...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... of VMESs in the 14.47-14.5 GHz (Earth-to-space) frequency band in the vicinity of radio astronomy... location, and the applicable coordination zone. Table 1—Applicable Radio Astronomy Service (RAS) Facilities... Astronomical Research Institute, Rosman, NC 35°11′59″ 82°52′19″ 160. U of Michigan Radio Astronomy...

  7. Effect of precipitation on choice of frequency for SEASAT scatterometer

    NASA Technical Reports Server (NTRS)

    Dome, G.

    1975-01-01

    Precipitation backscatter limits the effectiveness of a remote sensing radar in a satellite. Scatterometer operation on SEASAT is considered in one of the following frequency ranges: 12.5 GHz; 13.4-14.0 GHz; and 14.4-15.35 GHz. The effect of backscatter from precipitation in these frequency ranges is compared.

  8. 78 FR 26364 - Information Collections Being Submitted for Review and Approval to the Office of Management and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-06

    ... the radio line-of-sight of radio astronomy service (RAS) observatories observing in the 14.47-14.5 GHz... submit a radio frequency hazard analysis determining via calculation, simulation, or field measurement... Commission's radio frequency exposure criteria. ESAA applicants with ESAA terminals that will exceed...

  9. Phase reference holography of the Noto 32 m VLBI antenna

    NASA Astrophysics Data System (ADS)

    Tuccari, G.; Buttaccio, S.; Nicotra, G.

    2002-08-01

    Holographic measurements to determine deviations of the 32m Noto antenna with respect to an ideal parabolic surface have been performed at 11.5 GHz. An `ad hoc' system including a reference secondary antenna was built, and digital beacons coming from commercial TV satellites were used as signal sources. Results clearly showed significant deformations of the dish

  10. High Power High Efficiency Ka-Band Power Combiners for Solid-State Devices

    NASA Technical Reports Server (NTRS)

    Freeman, Jon C.; Wintucky, Edwin G.; Chevalier, Christine T.

    2006-01-01

    Wide-band power combining units for Ka-band are simulated for use as MMIC amplifier applications. Short-slot couplers as well as magic-tees are the basic elements for the combiners. Wide bandwidth (5 GHz) and low insertion (approx.0.2 dB) and high combining efficiencies (approx.90 percent) are obtained.

  11. 78 FR 1188 - Commercial Operations in the 3550-3650 MHz Band

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-08

    ... Citizens Broadband Radio Service under part 95 of its rules for shared small cell use in the 3550-3650 MHz... Satellite Service (FSS) users. The Commission also seeks comment on how the unique characteristics of small cells may help reduce the need for geographic protections and enable shared access of the 3.5 GHz...

  12. A search for interstellar nitrous oxide

    NASA Technical Reports Server (NTRS)

    Wilson, W. J.; Snyder, L. E.

    1981-01-01

    An extensive search for interstellar nitrous oxide (N2O) has been made at two different frequencies, 75.4 and 100.5 GHz, in a number of molecular sources. No N2O signal was detected; however, a number of other spectral lines including two new transitions of methyl formate and several new unidentified lines were measured.

  13. Analysis of electromagnetic pulse (EMP) measurements in the National Ignition Facility's target bay and chamber

    NASA Astrophysics Data System (ADS)

    Brown, C. G.; Clancy, T. J.; Eder, D. C.; Ferguson, W.; Throop, A. L.

    2013-11-01

    From May 2009 to the present we have recorded electromagnetic pulse (EMP) strength and spectrum (100 MHz - 5 GHz) in the target bay and chamber of the National Ignition Facility (NIF). The dependence of EMP strength and frequency spectrum on target type and laser energy is discussed. The largest EMP measured was for relatively low-energy, short-pulse (100 ps) flat targets.

  14. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Qu, H.; Zhang, T.; Han, X.; Xiang, H. M.; Wen, F.; Geng, K. N.; Wang, Y. M.; Kong, D. F.; Cai, J. Q.; Huang, C. B.; Gao, Y.; Gao, X.; Zhang, S.

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  15. All-optical Photonic Oscillator with High-Q Whispering Gallery Mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A.; Matsko, Andrey B.; Strekalov, Dmitry; Mohageg, Makan; Iltchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We demonstrated low threshold optical photonic hyper-parametric oscillator in a high-Q 10(exp 10) CaF2 whispering gallery mode resonator which generates stable 8.5 GHz signal. The oscillations result from the resonantly enhanced four wave mixing occurring due to Kerr nonlinearity of the material.

  16. 47 CFR 25.271 - Control of transmitting stations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Section 25.271 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.271 Control of transmitting stations. (a) The licensee of... the 10.7-14.5 GHz bands shall maintain an electronic web site bulletin board to list the...

  17. 47 CFR 25.271 - Control of transmitting stations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Section 25.271 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.271 Control of transmitting stations. (a) The licensee of... the 10.7-14.5 GHz bands shall maintain an electronic web site bulletin board to list the...

  18. 47 CFR 25.271 - Control of transmitting stations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Section 25.271 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.271 Control of transmitting stations. (a) The licensee of....5 GHz bands shall maintain an electronic web site bulletin board to list the satellite...

  19. 47 CFR 25.271 - Control of transmitting stations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Section 25.271 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.271 Control of transmitting stations. (a) The licensee of....5 GHz bands shall maintain an electronic web site bulletin board to list the satellite...

  20. 47 CFR 25.271 - Control of transmitting stations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Section 25.271 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.271 Control of transmitting stations. (a) The licensee of....5 GHz bands shall maintain an electronic web site bulletin board to list the satellite...

  1. Measuring the complex permittivity of poultry meat with a planar transmission-line sensor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A planar transmission-line sensor is used to measure the complex permittivity of chicken breast meat over the frequency range 0.5 – 5 GHz. Results for the permittivity of nine samples of chicken breast meat are compared to results obtained with a commercially available open-ended coaxial-line probe....

  2. Beyond Where to How: A Machine Learning Approach for Sensing Mobility Contexts Using Smartphone Sensors †

    PubMed Central

    Guinness, Robert E.

    2015-01-01

    This paper presents the results of research on the use of smartphone sensors (namely, GPS and accelerometers), geospatial information (points of interest, such as bus stops and train stations) and machine learning (ML) to sense mobility contexts. Our goal is to develop techniques to continuously and automatically detect a smartphone user's mobility activities, including walking, running, driving and using a bus or train, in real-time or near-real-time (<5 s). We investigated a wide range of supervised learning techniques for classification, including decision trees (DT), support vector machines (SVM), naive Bayes classifiers (NB), Bayesian networks (BN), logistic regression (LR), artificial neural networks (ANN) and several instance-based classifiers (KStar, LWLand IBk). Applying ten-fold cross-validation, the best performers in terms of correct classification rate (i.e., recall) were DT (96.5%), BN (90.9%), LWL (95.5%) and KStar (95.6%). In particular, the DT-algorithm RandomForest exhibited the best overall performance. After a feature selection process for a subset of algorithms, the performance was improved slightly. Furthermore, after tuning the parameters of RandomForest, performance improved to above 97.5%. Lastly, we measured the computational complexity of the classifiers, in terms of central processing unit (CPU) time needed for classification, to provide a rough comparison between the algorithms in terms of battery usage requirements. As a result, the classifiers can be ranked from lowest to highest complexity (i.e., computational cost) as follows: SVM, ANN, LR, BN, DT, NB, IBk, LWL and KStar. The instance-based classifiers take considerably more computational time than the non-instance-based classifiers, whereas the slowest non-instance-based classifier (NB) required about five-times the amount of CPU time as the fastest classifier (SVM). The above results suggest that DT algorithms are excellent candidates for detecting mobility contexts in smartphones

  3. Development of a plasma generator for a long pulse ion source for neutral beam injectors

    SciTech Connect

    Watanabe, K.; Dairaku, M.; Tobari, H.; Kashiwagi, M.; Inoue, T.; Hanada, M.; Jeong, S. H.; Chang, D. H.; Kim, T. S.; Kim, B. R.; Seo, C. S.; Jin, J. T.; Lee, K. W.; In, S. R.; Oh, B. H.; Kim, J.; Bae, Y. S.

    2011-06-15

    A plasma generator for a long pulse H{sup +}/D{sup +} ion source has been developed. The plasma generator was designed to produce 65 A H{sup +}/D{sup +} beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and {+-}7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm{sup 2}.

  4. Development of a plasma generator for a long pulse ion source for neutral beam injectors.

    PubMed

    Watanabe, K; Dairaku, M; Tobari, H; Kashiwagi, M; Inoue, T; Hanada, M; Jeong, S H; Chang, D H; Kim, T S; Kim, B R; Seo, C S; Jin, J T; Lee, K W; In, S R; Oh, B H; Kim, J; Bae, Y S

    2011-06-01

    A plasma generator for a long pulse H(+)/D(+) ion source has been developed. The plasma generator was designed to produce 65 A H(+)/D(+) beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and ±7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm(2).

  5. Lewis Investigates Frequency Sharing Between Future NASA Space Systems and Local Multipoint Distribution Systems in the 27-GHz Band

    NASA Technical Reports Server (NTRS)

    1997-01-01

    At the request of the Federal Communications Commission (FCC), the NASA Lewis Research Center undertook an intensive study to examine the feasibility of frequency sharing between future NASA space services and proposed Local Multipoint Distribution Systems (LMDS) in the 25.25- to 27.5-GHz band. This follows NASA's earlier involvement in the FCC's 1994 Negotiated Rule Making Committee which studied frequency sharing between Ka-band Fixed Satellite Services and LMDS in the 27.5- to 29.5-GHz band. LMDS is a terrestrial, cellular, wireless communication service primarily intended to provide television distribution from hub stations located within relatively small cells to fixed subscriber receivers. Some proposed systems, however, also plan to offer interactive services via subscriber-to-hub transmissions. LMDS providers anticipate that their systems will be a cost-effective alternative to cable television systems, especially in urban areas. LMDS proponents have expressed an interest in using frequencies below 27.5 GHz. NASA, however, plans to operate three types of space systems below 27.5 GHz. The H, I, and J follow-on satellites for the Tracking and Data Relay Satellite System (TDRSS), which are planned for launch beginning in 1999, are designed to receive high-data-rate transmissions (up to 800 Mbps) from low-Earth orbiting "user" spacecraft in the 25.25- to 27.5-GHz band. In this case, the potential interference is the aggregate interference from LMDS transmitters (both hubs and subscribers) into the TDRSS tracking receive beams as they sweep over the Earth's surface while tracking lower altitude user spacecraft.

  6. A high spatial resolution Stokes polarimeter for motional Stark effect imaging.

    PubMed

    Thorman, Alex; Michael, Clive; Howard, John

    2013-06-01

    We describe an enhanced temporally switched interfero-polarimeter that has been successfully deployed for high spatial resolution motional Stark effect imaging on the KSTAR superconducting tokamak. The system utilizes dual switching ferroelectric liquid crystal waveplates to image the full Stokes vector of elliptically polarized and Doppler-shifted Stark-Zeeman Balmer-alpha emission from high energy neutral beams injected into the magnetized plasma. We describe the optical system and compare its performance against a Mueller matrix model that takes account of non-ideal performance of the switching ferro-electric liquid crystal waveplates and other polarizing components. PMID:23822345

  7. The 1979-1980 eclipse of Zeta Aurigae. I - The circumstellar envelope

    NASA Technical Reports Server (NTRS)

    Chapman, R. D.

    1981-01-01

    A model of the K-star wind far from the K star, and its interaction with the B star, has been derived from a study of Mg(+) and C(+++) resonance lines in the spectrum of Zeta Aurigae during 1979 and 1980. A mass loss rate from the K star of 2 x 10 to the -8th solar masses/year is suggested by the data; the rate of accretion of the K supergiant's material by the B star then being such that the matter accreted over a period of ten years is of the order of the total mass of the photosphere of the B star.

  8. Characterization and calibration of a capacitive diaphragm gauge manometer for the measurement of dust particles in vacuum

    NASA Astrophysics Data System (ADS)

    Cho, S.-G.; Hong, S.-H.; Woo, H.-J.; Park, S.-J.; Park, E.-K.; Oh, Y.-S.; Kim, J.-W.; Chung, K.-S.

    2013-07-01

    A capacitive diaphragm gauge (CDG) has been modified to measure the amount of accumulated in-vessel dust in tokamaks. In order to pin point the mass load on the CDG, aluminum dish is used. Calibrations show that the CDG has a measurement range from 2.2 g to 6.7 g with a minimum detection mass of 30 mg. Long term stability of measured signal is obtained at least more than 12 h operation with the atmospheric pressure and under vacuum. The CDG will be installed in KSTAR (Korea Superconducting Tokamak Advanced Research) device in 2012 campaign to measure the amount of in-vessel dusts.

  9. A high spatial resolution Stokes polarimeter for motional Stark effect imaging

    SciTech Connect

    Thorman, Alex; Michael, Clive; Howard, John

    2013-06-15

    We describe an enhanced temporally switched interfero-polarimeter that has been successfully deployed for high spatial resolution motional Stark effect imaging on the KSTAR superconducting tokamak. The system utilizes dual switching ferroelectric liquid crystal waveplates to image the full Stokes vector of elliptically polarized and Doppler-shifted Stark-Zeeman Balmer-alpha emission from high energy neutral beams injected into the magnetized plasma. We describe the optical system and compare its performance against a Mueller matrix model that takes account of non-ideal performance of the switching ferro-electric liquid crystal waveplates and other polarizing components.

  10. Methods of Improving Internal-TIN Nb{sub 3}Sn for Fusion Applications

    SciTech Connect

    Pyon, T; Gregory, E.

    2002-08-29

    Development of a more reliable and economical high field material for ITER and TPX as well as LDK and KSTAR programs. The overall objective of this work is to provide the TPX/ITER programs and similar projects with an improved, reliable and economical high field Nb{sub 3}Sn multifilamentary conductor strand made by the internal-tin process. An effort will also be made to determine the reasons for the property changes taking place after various heat treatment cycles in an effort to develop optimized heat treatments for the various applications.

  11. Current Profile Measurements from Moderate to Strong Lower Hybrid Single-Pass Damping on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Mumgaard, R. T.; Wallace, G. M.; Scott, S. D.; Shiraiwa, S.; Faust, I.; Parker, R. R.

    2015-11-01

    Lower Hybrid Current Drive (LHCD) is an effective tool to non-inductively drive up to 100% of the plasma current on Alcator C-Mod. Measurements with an upgraded MSE diagnostic show that the fast-electron current profile is broader than the Ohmic current profile but still located the plasma core in agreement with strongly centrally peaked fast electron bremsstrahlung (FEB) measurements. Scans in a regime of high current drive efficiency across a range of density, LHCD power, launched n||, and plasma current show the driven current profile, FEB profile shapes, and current drive efficiency are sensitive only to total plasma current. Simulations using ray-tracing Fokker Planck codes show that the rays make 1-3 bounces through the plasma edge to bridge the spectral gap. Although in agreement with the total current, the simulations qualitatively disagree with experiment regarding current and FEB profiles as well as sensitivity to power and density. Simulations at higher plasma temperature and current predict stronger single-pass damping and preliminary experiments show increased current drive efficiency. Experiments to determine if the profile discrepancies persist when the ray bounces play a reduced role are planned, including companion experiments in D and He resulting in different edge plasma conditions. This work was performed on the Alcator C-Mod tokamak, a DoE Office of Science user facility, and is supported by USDoE awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  12. Review of recent experimental and modeling progress in the lower hybrid range of frequencies at ITER relevant parameters

    SciTech Connect

    Bonoli, Paul T.

    2014-02-12

    Progress in experiment and simulation capability in the lower hybrid range of frequencies (LHRF) at ITER relevant parameters is reviewed. Use of LH power in reactor devices is motivated in terms of its potential for efficient off-axis current profile control. Recent improvements in simulation capability including the development of full-wave field solvers, inclusion of the scrape off layer (SOL) in wave propagation codes, the use of coupled ray tracing / full-wave / 3D (r v{sub ⊥}, v{sub ∥}) Fokker Planck models, and the inclusion of nonlinear broadening effects in ray tracing / Fokker Planck codes are discussed. Experimental and modeling results are reviewed which are aimed at understanding the spectral gap problem in LH current drive (LHCD) and the density limit that has been observed in LHCD experiments. Physics mechanisms that could be operative in these experiments are discussed, including toroidally induced variations in the parallel wavenumber, nonlinear broadening of the pump wave, scattering of LH waves from density fluctuations in the SOL, and spectral broadening at the plasma edge via full-wave effects.

  13. Current drive for stability of thermonuclear plasma reactor

    NASA Astrophysics Data System (ADS)

    Amicucci, L.; Cardinali, A.; Castaldo, C.; Cesario, R.; Galli, A.; Panaccione, L.; Paoletti, F.; Schettini, G.; Spigler, R.; Tuccillo, A.

    2016-01-01

    To produce in a thermonuclear fusion reactor based on the tokamak concept a sufficiently high fusion gain together stability necessary for operations represent a major challenge, which depends on the capability of driving non-inductive current in the hydrogen plasma. This request should be satisfied by radio-frequency (RF) power suitable for producing the lower hybrid current drive (LHCD) effect, recently demonstrated successfully occurring also at reactor-graded high plasma densities. An LHCD-based tool should be in principle capable of tailoring the plasma current density in the outer radial half of plasma column, where other methods are much less effective, in order to ensure operations in the presence of unpredictably changes of the plasma pressure profiles. In the presence of too high electron temperatures even at the periphery of the plasma column, as envisaged in DEMO reactor, the penetration of the coupled RF power into the plasma core was believed for long time problematic and, only recently, numerical modelling results based on standard plasma wave theory, have shown that this problem should be solved by using suitable parameter of the antenna power spectrum. We show here further information on the new understanding of the RF power deposition profile dependence on antenna parameters, which supports the conclusion that current can be actively driven over a broad layer of the outer radial half of plasma column, thus enabling current profile control necessary for the stability of a reactor.

  14. Effects of the radial dependence of the fast electron diffusion coefficient on the current driven by lower-hybrid waves in tokamak

    SciTech Connect

    Zhang Xianmei; Wang Yanhui; Yu Limin; Shen Xin; Wang Jianbin

    2012-07-15

    The lower hybrid current drive (LHCD) is one of the promising methods not only for driving the non-inductive current required for steady-state tokamak operation, but also for controlling the plasma current profile to improve confinement in tokamak experiments. A direct consequence of experimental imperfection is difficult to obtain reliable estimate of the radial diffusion coefficient (D{sub st}) of the lower hybrid driven current. In this paper, the radial profile of D{sub st} is estimated to investigate its effect on the current driven by lower hybrid wave (LHW) in Experimental Advanced Superconducting Tokamak. Compared with the case of the constant radial diffusion coefficient, the efficiency of LHW driven current with the radial dependent diffusion coefficient D{sub st} ({rho}) becomes either higher or lower with respect to the plasma parameters, such as the density and the magnetic fluctuation. It is also found that the profiles of the LHW driven current are different. Therefore, it is necessary to consider the radial dependence of D{sub st} in order to get an accurate and reliable result in the numerical simulation of LHCD.

  15. Effects of the radial dependence of the fast electron diffusion coefficient on the current driven by lower-hybrid waves in tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, Xianmei; Wang, Yanhui; Yu, Limin; Shen, Xin; Wang, Jianbin

    2012-07-01

    The lower hybrid current drive (LHCD) is one of the promising methods not only for driving the non-inductive current required for steady-state tokamak operation, but also for controlling the plasma current profile to improve confinement in tokamak experiments. A direct consequence of experimental imperfection is difficult to obtain reliable estimate of the radial diffusion coefficient (Dst) of the lower hybrid driven current. In this paper, the radial profile of Dst is estimated to investigate its effect on the current driven by lower hybrid wave (LHW) in Experimental Advanced Superconducting Tokamak. Compared with the case of the constant radial diffusion coefficient, the efficiency of LHW driven current with the radial dependent diffusion coefficient Dst (ρ) becomes either higher or lower with respect to the plasma parameters, such as the density and the magnetic fluctuation. It is also found that the profiles of the LHW driven current are different. Therefore, it is necessary to consider the radial dependence of Dst in order to get an accurate and reliable result in the numerical simulation of LHCD.

  16. Scattering effects on lower hybrid wave propagation

    NASA Astrophysics Data System (ADS)

    Bertelli, N.; Phillips, C. K.; Valeo, E. J.; Wilson, J. R.; Baek, S. G.; Bonoli, P. T.; Parker, R. R.; Wallace, G.; Wright, J. C.; Harvey, R. W.; Smirnov, A. P.

    2012-10-01

    The effects of edge plasma density fluctuations on the scattering of lower hybrid (LH) waves are studied. Scattering can improve the penetration of LH waves into the plasma core due to the k upshift that occurs through the poloidal field (because the rotation of k induces a finite poloidal mode number). Scattering can also inhibit wave penetration depending on the density fluctuation levels, resulting in enhanced collisional absorption of the waves in the SOL at high density. These two effects might contribute, respectively, to resolving the ``spectral gap'' problem [Bonoli P. T. and R. C. Englade, Phys. Fluids 9 (1986) 2937] and the ``density limit'' in the efficiency of LHCD [Wallace G. et al., Phys. Plasmas 17 (2010) 082508]. The scattering model used is based on the work of Bonoli and Ott [Phys. Fluids 25 (1982) 361] that introduces an electromagnetic wave kinetic equation solved by a Monte Carlo technique. This equation has been implemented in the ray tracing code GENRAY, which explicitly includes the SOL region. A detailed analysis of this scattering model will be presented in comparison with the experimental observations of LHCD for Alcator C-Mod tokamak.

  17. Review of recent experimental and modeling progress in the lower hybrid range of frequencies at ITER relevant parameters

    SciTech Connect

    Bonoli, Paul T.

    2014-06-15

    Progress in experiment and simulation capability in the lower hybrid range of frequencies at ITER relevant parameters is reviewed. Use of LH power in reactor devices is motivated in terms of its potential for efficient off-axis current profile control. Recent improvements in simulation capability including the development of full-wave field solvers, inclusion of the scrape off layer (SOL) in wave propagation codes, the use of coupled ray tracing/full-wave/3D (r v{sub ⊥}, v{sub //}) Fokker Planck models, and the inclusion of wave scattering as well as nonlinear broadening effects in ray tracing / Fokker Planck codes are discussed. Experimental and modeling results are reviewed which are aimed at understanding the spectral gap problem in LH current drive (LHCD) and the density limit that has been observed and mitigated in LHCD experiments. Physics mechanisms that could be operative in these experiments are discussed, including toroidally induced variations in the parallel wavenumber, nonlinear broadening of the pump wave, scattering of LH waves from density fluctuations in the SOL, and spectral broadening at the plasma edge via full-wave effects.

  18. Study on lower hybrid current drive efficiency at high density towards long-pulse regimes in Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Li, M. H.; Ding, B. J.; Zhang, J. Z.; Gan, K. F.; Wang, H. Q.; Peysson, Y.; Decker, J.; Zhang, L.; Wei, W.; Li, Y. C.; Wu, Z. G.; Ma, W. D.; Jia, H.; Chen, M.; Yang, Y.; Feng, J. Q.; Wang, M.; Xu, H. D.; Shan, J. F.; Liu, F. K.

    2014-06-01

    Significant progress on both L- and H-mode long-pulse discharges has been made recently in Experimental Advanced Superconducting Tokamak (EAST) with lower hybrid current drive (LHCD) [J. Li et al., Nature Phys. 9, 817 (2013) And B. N. Wan et al., Nucl. Fusion 53, 104006 (2013).]. In this paper, LHCD experiments at high density in L-mode plasmas have been investigated in order to explore possible methods of improving current drive (CD) efficiency, thus to extend the operational space in long-pulse and high performance plasma regime. It is observed that the normalized bremsstrahlung emission falls much more steeply than 1/ne_av (line-averaged density) above ne_av = 2.2 × 1019 m-3 indicating anomalous loss of CD efficiency. A large broadening of the operating line frequency (f = 2.45 GHz), measured by a radio frequency (RF) probe located outside the EAST vacuum vessel, is generally observed during high density cases, which is found to be one of the physical mechanisms resulting in the unfavorable CD efficiency. Collisional absorption of lower hybrid wave in the scrape off layer (SOL) may be another cause, but this assertion needs more experimental evidence and numerical analysis. It is found that plasmas with strong lithiation can improve CD efficiency largely, which should be benefited from the changes of edge parameters. In addition, several possible methods are proposed to recover good efficiency in future experiments for EAST.

  19. An assessment of full wave effects on the propagation and absorption of lower hybrid wavesa)

    NASA Astrophysics Data System (ADS)

    Wright, J. C.; Bonoli, P. T.; Schmidt, A. E.; Phillips, C. K.; Valeo, E. J.; Harvey, R. W.; Brambilla, M. A.

    2009-07-01

    Lower hybrid (LH) waves (Ωci≪ω≪Ωce, where Ωi ,e≡Zi ,eeB/mi ,ec) have the attractive property of damping strongly via electron Landau resonance on relatively fast tail electrons and consequently are well-suited to driving current. Established modeling techniques use Wentzel-Kramers-Brillouin (WKB) expansions with self-consistent non-Maxwellian distributions. Higher order WKB expansions have shown some effects on the parallel wave number evolution and consequently on the damping due to diffraction [G. Pereverzev, Nucl. Fusion 32, 1091 (1991)]. A massively parallel version of the TORIC full wave electromagnetic field solver valid in the LH range of frequencies has been developed [J. C. Wright et al., Comm. Comp. Phys. 4, 545 (2008)] and coupled to an electron Fokker-Planck solver CQL3D [R. W. Harvey and M. G. McCoy, in Proceedings of the IAEA Technical Committee Meeting, Montreal, 1992 (IAEA Institute of Physics Publishing, Vienna, 1993), USDOC/NTIS Document No. DE93002962, pp. 489-526] in order to self-consistently evolve nonthermal electron distributions characteristic of LH current drive (LHCD) experiments in devices such as Alcator C-Mod and ITER (B0≈5 T, ne0≈1×1020 m-3). These simulations represent the first ever self-consistent simulations of LHCD utilizing both a full wave and Fokker-Planck calculation in toroidal geometry.

  20. Development of long pulse RF heating and current drive for H-mode scenarios with metallic walls in WEST

    SciTech Connect

    Ekedahl, Annika Bourdelle, Clarisse; Artaud, Jean-François; Bernard, Jean-Michel; Bufferand, Hugo; Colas, Laurent; Decker, Joan; Delpech, Léna; Dumont, Rémi; Goniche, Marc; Helou, Walid; Hillairet, Julien; Lombard, Gilles; Magne, Roland; Mollard, Patrick; Nardon, Eric; Peysson, Yves; Tsitrone, Emmanuelle

    2015-12-10

    The longstanding expertise of the Tore Supra team in long pulse heating and current drive with radiofrequency (RF) systems will now be exploited in the WEST device (tungsten-W Environment in Steady-state Tokamak) [1]. WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m{sup 2}), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW / 30 s at I{sub P} = 0.8 MA) or high fluence (up to 10 MW / 1000 s at I{sub P} = 0.6 MA) [2], all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). This paper gives a description of the ICRH and LHCD systems in WEST, together with the modelling of the power deposition of the RF waves in the WEST-scenarios.

  1. Development of long pulse RF heating and current drive for H-mode scenarios with metallic walls in WEST

    NASA Astrophysics Data System (ADS)

    Ekedahl, Annika; Bourdelle, Clarisse; Artaud, Jean-François; Bernard, Jean-Michel; Bufferand, Hugo; Colas, Laurent; Decker, Joan; Delpech, Léna; Dumont, Rémi; Goniche, Marc; Helou, Walid; Hillairet, Julien; Lombard, Gilles; Magne, Roland; Mollard, Patrick; Nardon, Eric; Peysson, Yves; Tsitrone, Emmanuelle

    2015-12-01

    The longstanding expertise of the Tore Supra team in long pulse heating and current drive with radiofrequency (RF) systems will now be exploited in the WEST device (tungsten-W Environment in Steady-state Tokamak) [1]. WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m2), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW / 30 s at IP = 0.8 MA) or high fluence (up to 10 MW / 1000 s at IP = 0.6 MA) [2], all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). This paper gives a description of the ICRH and LHCD systems in WEST, together with the modelling of the power deposition of the RF waves in the WEST-scenarios.

  2. Sensitivity of magnetic field-line pitch angle measurements to sawtooth events in tokamaks

    NASA Astrophysics Data System (ADS)

    Ko, J.

    2016-11-01

    The sensitivity of the pitch angle profiles measured by the motional Stark effect (MSE) diagnostic to the evolution of the safety factor, q, profiles during the tokamak sawtooth events has been investigated for Korea Superconducting Tokamak Advanced Research (KSTAR). An analytic relation between the tokamak pitch angle, γ, and q estimates that Δγ ˜ 0.1° is required for detecting Δq ˜ 0.05 near the magnetic axis (not at the magnetic axis, though). The pitch angle becomes less sensitive to the same Δq for the middle and outer regions of the plasma (Δγ ˜ 0.5°). At the magnetic axis, it is not straightforward to directly relate the γ sensitivity to Δq since the gradient of γ(R), where R is the major radius of the tokamak, is involved. Many of the MSE data obtained from the 2015 KSTAR campaign, when calibrated carefully, can meet these requirements with the time integration down to 10 ms. The analysis with the measured data shows that the pitch angle profiles and their gradients near the magnetic axis can resolve the change of the q profiles including the central safety factor, q0, during the sawtooth events.

  3. Development progresses of radio frequency ion source for neutral beam injector in fusion devices

    NASA Astrophysics Data System (ADS)

    Chang, D. H.; Jeong, S. H.; Kim, T. S.; Park, M.; Lee, K. W.; In, S. R.

    2014-02-01

    A large-area RF (radio frequency)-driven ion source is being developed in Germany for the heating and current drive of an ITER device. Negative hydrogen ion sources are the major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen (deuterium) ions have been successfully developed for the neutral beam heating systems at IPP (Max-Planck-Institute for Plasma Physics) in Germany. The first long-pulse ion source has been developed successfully with a magnetic bucket plasma generator including a filament heating structure for the first NBI system of the KSTAR tokamak. There is a development plan for an RF ion source at KAERI to extract the positive ions, which can be applied for the KSTAR NBI system and to extract the negative ions for future fusion devices such as the Fusion Neutron Source and Korea-DEMO. The characteristics of RF-driven plasmas and the uniformity of the plasma parameters in the test-RF ion source were investigated initially using an electrostatic probe.

  4. Filterscopes: Spectral line monitors for long-pulse plasma devices

    SciTech Connect

    Brooks, N. H.; Colchin, R. J.; Fehling, D. T.; Hillis, D. L.; Mu, Y.; Unterberg, E.

    2008-10-15

    A photomultiplier (PMT)-based diagnostic system for monitoring spectral lines along multiple viewchords, named the 'Filterscope' [R. J. Colchin et al., Rev. Sci. Instrum. 74, 2068 (2003)], is currently in use at the DIII-D, NSTX, and CDX-U fusion plasma devices in the US, and has been installed at the KSTAR device in Korea. This diagnostic has recently been upgraded for application to long-pulse devices, such as KSTAR, EAST in China, and the future ITER in France. A new data acquisition system, employing the PXI instrumentation platform with an embedded Windows microprocessor controller, can simultaneously record up to 72 channels at 100 kHz sampling rates for plasma periods lasting up to 20 min. Based on the average signal level during an adjustable time interval (100 ms in the present DIII-D implementation), the controller digitally adjusts PMT dynode voltage throughout the course of a discharge, thereby maintaining the output signals at a level where they are neither saturated nor dominated by digitizer noise. The new system's ability to accommodate large variations in source strength, discharge to discharge and within a single discharge, has proved particularly valuable during DIII-D operations, since changes between top, bottom, and double-null divertor magnetic configurations lead to large temporal variations in signal brightness.

  5. Polarimetric spectra analysis for tokamak pitch angle measurements

    NASA Astrophysics Data System (ADS)

    Ko, J.; Chung, J.; Lange, A. G. G.; de Bock, M. F. M.

    2013-10-01

    Measurements of the internal magnetic field structures using conventional polarimetric approaches are considered extremely challenging in fusion-reactor environments whereas the information on current density profiles is essential to establish steady-state and advance operation scenarios in such reactor-relevant devices. Therefore, on ITER a hybrid system is proposed for the current density measurements that uses both polarimetry and spectral measurements. The spectrum-based approaches have been tested in the Korea Superconducting Tokamak Advanced Research (KSTAR) during the past two plasma campaigns. As such, KSTAR is a test-bed for the proposed ITER hybrid system. Measurements in the plasma core are based on the motional Stark effect (MSE) spectrum of the neutral beam emission. For the edge profiles, the Zeeman effect (ZE) acting on the lithium emission spectrum of the newly installed (2013) Lithium-beam-diagnostic is exploited. The neutral beam emission spectra, complicated by the multi-ion-source beam injection, are successfully fitted making use of the data provided by the Atomic Data and Analysis Structure (ADAS) database package. This way pitch angle profiles could be retrieved from the beam emission spectra. With the same spectrometer/CCD hardware as on MSE, but with a different wavelength range and different lines of sight, the first ZE spectrum measurements have been made. The Zeeman splitting comparable to and greater than the instrumental broadening has been routinely detected at high toroidal field operations ( ~ 3 Tesla).

  6. First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Yu Yaowei; Kim, Young-Ok; Kim, Hak-Kun; Kim, Hong-Tack; Kim, Woong-Chae; Kim, Kwang-Pyo; Son, Soo-Hyun; Bang, Eun-Nam; Hong, Suk-Ho; Yoon, Si-Woo; Zhuang Huidong; Chen Zhongyong

    2012-12-15

    Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is {approx}3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D{sub 2} MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.

  7. Analysis of line integrated electron density using plasma position data on Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Nam, Y. U.; Chung, J.

    2010-10-15

    A 280 GHz single-channel horizontal millimeter-wave interferometer system has been installed for plasma electron density measurements on the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This system has a triangular beam path that does not pass through the plasma axis due to geometrical constraints in the superconducting tokamak. The term line density on KSTAR has a different meaning from the line density of other tokamaks. To estimate the peak density and the mean density from the measured line density, information on the position of the plasma is needed. The information has been calculated from tangentially viewed visible images using the toroidal symmetry of the plasma. Interface definition language routines have been developed for this purpose. The calculated plasma position data correspond well to calculation results from magnetic analysis. With the position data and an estimated plasma profile, the peak density and the mean density have been obtained from the line density. From these results, changes of plasma density themselves can be separated from effects of the plasma movements, so they can give valuable information on the plasma status.

  8. First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research

    NASA Astrophysics Data System (ADS)

    Yu, Yaowei; Kim, Young-Ok; Kim, Hak-Kun; Kim, Hong-Tack; Kim, Woong-Chae; Kim, Kwang-Pyo; Son, Soo-Hyun; Bang, Eun-Nam; Zhuang, Huidong; Chen, Zhongyong; Hong, Suk-Ho; Yoon, Si-Woo

    2012-12-01

    Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is ˜3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D2 MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.

  9. Analysis of neutral hydrogenic emission spectra in a tokamak

    NASA Astrophysics Data System (ADS)

    Ko, J.; Chung, J.; Jaspers, R. J. E.

    2015-10-01

    Balmer-α radiation by the excitation of thermal and fast neutral hydrogenic particles has been investigated in a magnetically confined fusion device, or tokamak, from the Korea Superconducting Tokamak Advanced Research (KSTAR). From the diagnostic point of view, the emission from thermal neutrals is associated with passive spectroscopy and that from energetic neutrals that are usually injected from the outside of the tokamak to the active spectroscopy. The passive spectroscopic measurement for the thermal Balmer-α emission from deuterium and hydrogen estimates the relative concentration of hydrogen in a deuterium-fueled plasma and therefore, makes a useful tool to monitor the vacuum wall condition. The ratio of hydrogen to deuterium obtained from this measurement qualitatively correlates with the energy confinement of the plasma. The Doppler-shifted Balmer-α components from the fast neutrals features the spectrum of the motional Stark effect (MSE) which is an essential principle for the measurement of the magnetic pitch angle profile. Characterization of this active MSE spectra, especially with multiple neutral beam lines crossing along the observation line of sight, has been done for the guideline of the multi-ion-source heating beam operation and for the optimization of the narrow bandpass filters that are required for the polarimeter-based MSE diagnostic system under construction at KSTAR.

  10. First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research.

    PubMed

    Yu, Yaowei; Kim, Young-Ok; Kim, Hak-Kun; Kim, Hong-Tack; Kim, Woong-Chae; Kim, Kwang-Pyo; Son, Soo-Hyun; Bang, Eun-Nam; Zhuang, Huidong; Chen, Zhongyong; Hong, Suk-Ho; Yoon, Si-Woo

    2012-12-01

    Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is ~3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D(2) MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.

  11. Development progresses of radio frequency ion source for neutral beam injector in fusion devices.

    PubMed

    Chang, D H; Jeong, S H; Kim, T S; Park, M; Lee, K W; In, S R

    2014-02-01

    A large-area RF (radio frequency)-driven ion source is being developed in Germany for the heating and current drive of an ITER device. Negative hydrogen ion sources are the major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen (deuterium) ions have been successfully developed for the neutral beam heating systems at IPP (Max-Planck-Institute for Plasma Physics) in Germany. The first long-pulse ion source has been developed successfully with a magnetic bucket plasma generator including a filament heating structure for the first NBI system of the KSTAR tokamak. There is a development plan for an RF ion source at KAERI to extract the positive ions, which can be applied for the KSTAR NBI system and to extract the negative ions for future fusion devices such as the Fusion Neutron Source and Korea-DEMO. The characteristics of RF-driven plasmas and the uniformity of the plasma parameters in the test-RF ion source were investigated initially using an electrostatic probe. PMID:24593580

  12. Density limits investigation and high density operation in EAST tokamak

    NASA Astrophysics Data System (ADS)

    Zheng, Xingwei; Li, Jiangang; Hu, Jiansheng; Liu, Haiqing; Jie, Yinxian; Wang, Shouxin; Li, Jiahong; Duan, Yanming; Li, Miaohui; Li, Yongchun; Zhang, Ling; Ye, Yang; Yang, Qingquan; Zhang, Tao; Cheng, Yingjie; Xu, Jichan; Wang, Liang; Xu, Liqing; Zhao, Hailin; Wang, Fudi; Lin, Shiyao; Wu, Bin; Lyu, Bo; Xu, Guosheng; Gao, Xiang; Shi, Tonghui; He, Kaiyang; Lan, Heng; Chu, Nan; Cao, Bin; Sun, Zhen; Zuo, Guizhong; Ren, Jun; Zhuang, Huidong; Li, Changzheng; Yuan, Xiaolin; Yu, Yaowei; Wang, Houyin; Chen, Yue; Wu, Jinhua; EAST Team

    2016-05-01

    Increasing the density in a tokamak is limited by the so-called density limit, which is generally performed as an appearance of disruption causing loss of plasma confinement, or a degradation of high confinement mode which could further lead to a H  →  L transition. The L-mode and H-mode density limit has been investigated in EAST tokamak. Experimental results suggest that density limits could be triggered by either edge cooling or excessive central radiation. The L-mode density limit disruption is generally triggered by edge cooling, which leads to the current profile shrinkage and then destabilizes a 2/1 tearing mode, ultimately resulting in a disruption. The L-mode density limit scaling agrees well with the Greenwald limit in EAST. The observed H-mode density limit in EAST is an operational-space limit with a value of 0.8∼ 0.9{{n}\\text{GW}} . High density H-mode heated by neutral beam injection (NBI) and lower hybrid current drive (LHCD) are analyzed, respectively. The constancy of the edge density gradients in H-mode indicates a critical limit caused perhaps by e.g. ballooning induced transport. The maximum density is accessed at the H  →  L transition which is generally caused by the excessive core radiation due to high Z impurities (Fe, Cu). Operating at a high density (>2.8× {{10}19} {{\\text{m}}-3} ) is favorable for suppressing the beam shine through NBI. High density H-mode up to 5.3× {{10}19}{{\\text{m}}-3}~≤ft(∼ 0.8{{n}\\text{GW}}\\right) could be sustained by 2 MW 4.6 GHz LHCD alone, and its current drive efficiency is studied. Statistics show that good control of impurities and recycling facilitate high density operation. With careful control of these factors, high density up to 0.93{{n}\\text{GW}} stable H-mode operation was carried out heated by 1.7 MW LHCD and 1.9 MW ion cyclotron resonance heating with supersonic molecular beam injection fueling.

  13. Radially Localized Measurements of Superthermal Electrons Using Obilique Ece

    NASA Astrophysics Data System (ADS)

    Preische, Sherrie Anne

    1995-01-01

    In the effort to design a tokamak which will make a more compact and economically attractive fusion energy reactor, tokamak regimes are envisioned in which radial profiles of the density, temperature, and current are controlled. Lower Hybrid Current Drive is one of the most flexible and proven means of controlling the plasma current profile. In order to develop a better understanding of how, to what extent, and under what conditions LHCD can be used to tailor the current profile, the radial profile and velocity distribution of the fast current-carrying electrons and their time evolution must be known. Spacially localized information about the fast electron distribution function is difficult to obtain. The electron calcitrant resonance, through its sensitivity to the magnetic field as well as to the frequency and angle of observation, provides a means of probing the fast electron distribution function in detail. A new and unique diagnostic has been developed, installed, and operated on the PBX -M tokamak to measure the Electron Cyclotron Emission from these fast electrons. An oblique horizontal view of upshifted cyclotron emission in the midplane gives radial as well as velocity space information about the fast electrons by utilizing the sensitivity of the electron cyclotron resonance. Emission in extraordinary (X)-mode at frequencies refracted by the right-hand cutoff is radially localized. An experiment has been performed in which quasi-X mode emission in the range 60-90 GHz is observed through a focusing gaussian lens antenna at a 57^ circ angle to the toroidal magnetic field. Using the sensitivity of the resonance condition to small changes in frequency and field, radially localized moments. E_ parallel, T_ |, n_{sth}, of the fast electron distribution function are found by a Bayesian analysis method. The evolution of the current profile obtained from these measurements is examined in detail. After the LHCD is turned off, the dynamics are found to be

  14. High density LHRF experiments in Alcator C-Mod and implications for reactor scale devices

    NASA Astrophysics Data System (ADS)

    Baek, S. G.; Parker, R. R.; Bonoli, P. T.; Shiraiwa, S.; Wallace, G. M.; LaBombard, B.; Faust, I. C.; Porkolab, M.; Whyte, D. G.

    2015-04-01

    Parametric decay instabilities (PDI) appear to be an ubiquitous feature of lower hybrid current drive (LHCD) experiments at high density. In density ramp experiments in Alcator C-Mod and other machines the onset of PDI activity has been well correlated with a decrease in current drive efficiency and production of fast electron bremsstrahlung. However whether PDI is the primary cause of the ‘density limit’, and if so by exactly what mechanism (beyond the obvious one of pump depletion) has not been clearly established. In order to further understand the connection, the frequency spectrum of PDI activity occurring during Alcator C-Mod LHCD experiments has been explored in detail by means of a number of RF probes distributed around the periphery of the C-Mod tokamak including a probe imbedded in the inner wall. The results show that (i) the excited spectra consists mainly of a few discrete ion cyclotron (IC) quasi-modes, which have higher growth than the ion sound branch; (ii) PDI activity can begin either at the inner or outer wall, depending on magnetic configuration; (iii) the frequencies of the IC quasi-modes correspond to the magnetic field strength close to the low-field side (LFS) or high-field side separatrix; and (iv) although PDI activity may initiate near the inner separatrix, the loss in fast electron bremsstrahlung is best correlated with the appearance of IC quasi-modes characteristic of the magnetic field strength near the LFS separatrix. These data, supported by growth rate calculations, point to the importance of the LFS scrape-off layer (SOL) density in determining PDI onset and degradation in current drive efficiency. By minimizing the SOL density it is possible to extend the core density regime over which PDI can be avoided, thus potentially maximizing the effectiveness of LHCD at high density. Increased current drive efficiency at high density has been achieved in FTU and EAST through lithium coating and special fuelling methods, and in recent

  15. Computational algorithms for simulations in atmospheric optics.

    PubMed

    Konyaev, P A; Lukin, V P

    2016-04-20

    A computer simulation technique for atmospheric and adaptive optics based on parallel programing is discussed. A parallel propagation algorithm is designed and a modified spectral-phase method for computer generation of 2D time-variant random fields is developed. Temporal power spectra of Laguerre-Gaussian beam fluctuations are considered as an example to illustrate the applications discussed. Implementation of the proposed algorithms using Intel MKL and IPP libraries and NVIDIA CUDA technology is shown to be very fast and accurate. The hardware system for the computer simulation is an off-the-shelf desktop with an Intel Core i7-4790K CPU operating at a turbo-speed frequency up to 5 GHz and an NVIDIA GeForce GTX-960 graphics accelerator with 1024 1.5 GHz processors.

  16. Radio-Frequency Performance of Epitaxial Graphene Field-Effect Transistors on Sapphire Substrates

    NASA Astrophysics Data System (ADS)

    Liu, Qing-Bin; Yu, Cui; Li, Jia; Song, Xu-Bo; He, Ze-Zhao; Lu, Wei-Li; Gu, Guo-Dong; Wang, Yuan-Gang; Feng, Zhi-Hong

    2014-07-01

    We report dc and the first-ever measured small signal rf performance of epitaxial graphene field-effect transistors (GFETs), where the epitaxial graphene is grown by chemical vapor deposition (CVD) on a 2-inch c-plane sapphire substrate. Our epitaxial graphene material has a good flatness and uniformity due to the low carbon concentration during the graphene growth. With a gate length Lg = 100 nm, the maximum drain source current Ids and peak transconductance gm reach 0.92 A/mm and 0.143 S/mm, respectively, which are the highest results reported for GFETs directly grown on sapphire. The extrinsic cutoff frequency (fT) and maximum oscillation frequency (fmax) of the device are 12 GHz and 9.5 GHz, and up to 32 GHz and 21.5 GHz after de-embedding, respectively. Our work proves that epitaxial graphene on sapphire substrates is a promising candidate for rf electronics.

  17. Computational algorithms for simulations in atmospheric optics.

    PubMed

    Konyaev, P A; Lukin, V P

    2016-04-20

    A computer simulation technique for atmospheric and adaptive optics based on parallel programing is discussed. A parallel propagation algorithm is designed and a modified spectral-phase method for computer generation of 2D time-variant random fields is developed. Temporal power spectra of Laguerre-Gaussian beam fluctuations are considered as an example to illustrate the applications discussed. Implementation of the proposed algorithms using Intel MKL and IPP libraries and NVIDIA CUDA technology is shown to be very fast and accurate. The hardware system for the computer simulation is an off-the-shelf desktop with an Intel Core i7-4790K CPU operating at a turbo-speed frequency up to 5 GHz and an NVIDIA GeForce GTX-960 graphics accelerator with 1024 1.5 GHz processors. PMID:27140113

  18. High Power Co-Axial Coupler

    SciTech Connect

    Neubauer, M.; Dudas, A.; Rimmer, Robert A.; Guo, Jiquan; Williams, R. Scott

    2013-12-01

    A very high power Coax RF Coupler (MW-Level) is very desirable for a number of accelerator and commercial applications. For example, the development of such a coupler operating at 1.5 GHz may permit the construction of a higher-luminosity version of the Electron-Ion Collider (EIC) being planned at JLab. Muons, Inc. is currently funded by a DOE STTR grant to develop a 1.5-GHz high-power doublewindowcoax coupler with JLab (about 150 kW). Excellent progress has been made on this R&D project, so we propose an extension of this development to build a very high power coax coupler (MW level peak power and a max duty factor of about 4%). The dimensions of the current coax coupler will be scaled up to provide higher power capability.

  19. SIMILAR RADIATION MECHANISM IN GAMMA-RAY BURSTS AND BLAZARS: EVIDENCE FROM TWO LUMINOSITY CORRELATIONS

    SciTech Connect

    Wang, F. Y.; Yi, S. X.; Dai, Z. G.

    2014-05-01

    Active galactic nuclei and gamma-ray bursts (GRBs) are powerful astrophysical events with relativistic jets. In this Letter, the broadband spectral properties of GRBs and well-observed blazars are compared. The distribution of GRBs is consistent with the well-known blazar sequence including the νL {sub ν}(5 GHz) – α{sub RX} and νL {sub ν}(5 GHz) – ν{sub peak} correlations, where α{sub RX} is defined as the broadband spectral slope in radio-to-X-ray bands, and ν{sub peak} is defined as the spectral peak frequency. Moreover, GRBs occupy the low radio luminosity end of these sequences. These two correlations suggest that GRBs could have a radiation process, i.e., synchrotron radiation, similar to blazars both in the prompt emission and afterglow phases.

  20. VizieR Online Data Catalog: Optical IDs of JVAS using APM (Snellen+ 2002)

    NASA Astrophysics Data System (ADS)

    Snellen, I. A. G.; McMahon, R. G.; Hook, I. M.; Browne, I. W. A.

    2002-01-01

    Files list1, list2, and list3 contain the lists of flat spectrum radio sources with their optical identifications from the APM (Automated Plate Measurement Facility at Cambridge) catalogue. List1 corresponds to the sources which are part of both the complete JVAS++ (a new complete sample constructed with selection criteria similar to those of JVAS -- Jodrell Bank VLA Astrometric Survey: S5GHz>200mJy, α1.4-5GHz>-0.5), and with the use of the more accurate GB6 and NVSS surveys) and original JVAS sample, List2 corresponds to sources which are only part of JVAS++, and List3 to sources which are only part of JVAS. The combination of List1 and List2 is a complete sample with S6cm>200mJy. (3 data files).

  1. THE CRAB PULSAR AT CENTIMETER WAVELENGTHS. I. ENSEMBLE CHARACTERISTICS

    SciTech Connect

    Hankins, T. H.; Eilek, J. A.; Jones, G.

    2015-04-01

    We have observed the pulsar in the Crab Nebula at high radio frequencies and high time resolution. We present continuously sampled data at 640 ns time resolution and individual bright pulses recorded at down to 0.25 ns time resolution. Combining our new data with previous data from our group and from the literature shows the dramatic changes in the pulsar’s radio emission between low and high radio frequencies. Below about 5 GHz the mean profile is dominated by the bright Main Pulse and Low-Frequency Interpulse. Everything changes, however, above about 5 GHz; the Main Pulse disappears and the mean profile of the Crab pulsar is dominated by the High-Frequency Interpulse (which is quite different from its low-frequency counterpart) and the two High-Frequency Components. We present detailed observational characteristics of these different components which future models of the pulsar’s magnetosphere must explain.

  2. Intercomparison of synthetic- and real-aperture radar observations of Arctic sea ice during winter MIZEX '87

    NASA Technical Reports Server (NTRS)

    Schuchmann, R. A.; Onstott, R. G.; Sutherland, L. L.; Wackerman, C. C.

    1988-01-01

    Active microwave measurements were made of various sea ice forms in March and April 1987 during the Marginal Ice Zone Experiment, at 1, 5, 10, 18, and 35 GHz using a synthetic aperture radar (SAR) and helicopter and ship-based scatterometers. The X-band (9.8 GHz) SAR data were compared to the scatterometer data and it was determined that for 5 GHz and higher frequencies both the SAR and scatterometers can differentiate open water, new ice (5 to 30 cm), first-year ice with rubble (0.60 -1.5 m), and multiyear ice. The analysis further confirmed that the C-band (5 GHz) SAR's flying on ESA ERS-1 and Radarsat will differentiate the mentioned ice types.

  3. Full wave analysis and miniaturization of microstrip antenna on ferrimagnetics substrates

    NASA Astrophysics Data System (ADS)

    Lavor, Otávio Paulino; Fernandes, Humberto Cesar Chaves

    2016-02-01

    This paper presents the miniaturization of the microstrip antenna on ferrimagnetic substrate for operate at a frequency of 2.5 GHz, where the full wave method Transverse Transmission Line-TTL is used it for obtain resonance frequency. For validate this method in these substrates, the results as function of DC magnetic field are shown. When the field is 132.6 AT/m, the value of reference is 151.7 MHz and the value of TTL is 151.3 MHz. The dimensions are obtained for the frequency of 2.5 GHz and a comparison is done with ferrites and conventional substrate, showing a reduction in volume of the antenna of 2808.96 mm3 for 0.39 mm3 when the ferrites are used.

  4. Monitoring variations of biological impedances using microwave Doppler radar.

    PubMed

    Thansandote, A; Stuchly, S S; Smith, A M

    1983-08-01

    A microwave Doppler radar for continuously monitoring time-varying biological impedances is described. The radar compares the phase of the signal scattered from a region of biological tissue with that of the transmitted signal. The phase changes of the scattered signal are an indication of the net impedance changes within the test region due to various physiological processes, for example, the displacements of blood vessels during the cardiac cycle. A Doppler radar, equipped with a matched antenna, was tested with a simulation model and its detection characteristic was found to be a sinusoidal function of the antenna-object spacing. Tests with healthy human subjects were also performed at 3 GHz and 10.5 GHz. It was found that the 3 GHz Doppler radar has significantly greater penetration in tissues but is less sensitive to changes of the biological impedance than the 10.5 GHz system.

  5. NGC 1976 in the Radio Range with the Green Bank Telescope

    NASA Astrophysics Data System (ADS)

    Wilson, Thomas L.; Bania, Thomas M.; Balser, Dana S.

    2015-01-01

    NGC 1976 (Orion A) is the best studied HII region in the Milky Way and therefore it is often used to test models of HII regions. In particular, the radial dependence of the electron temperature is able to distinguish between different models. Optical determinations of electron temperature in the outer regions are affected by scattered light from the center. We have observed the radio recombination line (RRL) and continuum emission near 5 GHz at 4 arc minutes East, West and South of the peak HII region emission in NGC 1976 using the Green Bank Telescope (GBT). The Full Width to Half Power at the observing frequency, 5 GHz, was 2 arc minutes. The result is that the average electron temperature for these offset positions is = 7200 ± 300 K, significantly lower than the electron temperature of the peak position = 8200 ± 300 K, consistent with the HII region model of Wilson et al. (2012).

  6. Hybrid CATV/16-QAM OFDM in-building networks over SMF and GI-POF transport.

    PubMed

    Peng, Hsiao-Chun; Su, Heng-Sheng; Lu, Hai-Han; Li, Chung-Yi; Peng, Peng-Chun; Wu, Shang-Hua; Chang, Ching-Hung

    2011-05-01

    A hybrid CATV/16-QAM OFDM in-building network over a combination of single-mode fiber (SMF) and graded-index plastic optical fiber (GI-POF) transport is proposed and experimentally demonstrated with good qualities of service. In this system, a 1556 nm optical signal is directly transmitted along with two fiber spans (20-km SMF + 25-m GI-POF). Without using any wavelength conversion or bridge circuit between SMF and POF connection, error free transmissions with sufficient low bit error rate (BER) values are achieved for 2.5 Gbps/2.5 GHz and 5 Gbps/2.5 GHz OFDM signals; as well as good performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) are obtained for CATV one. This proposed network reveals an outstanding one with economy and convenience to be installed.

  7. A novel slotted helix slow-wave structure for high power Ka-band traveling-wave tubes

    NASA Astrophysics Data System (ADS)

    Liu, Lu-Wei; Wei, Yan-Yu; Wang, Shao-Meng; Hou, Yan; Yin, Hai-Rong; Zhao, Guo-Qing; Duan, Zhao-Yun; Xu, Jin; Gong, Yu-Bin; Wang, Wen-Xiang; Yang, Ming-Hua

    2013-10-01

    A novel slotted helix slow-wave structure (SWS) is proposed to develop a high power, wide-bandwidth, and high reliability millimeter-wave traveling-wave tube (TWT). This novel structure, which has higher heat capacity than a conventional helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix tape. In this paper, the electromagnetic characteristics and the beam-wave interaction of this novel structure operating in the Ka-band are investigated. From our calculations, when the designed beam voltage and beam current are set to be 18.45 kV and 0.2 A, respectively, this novel circuit can produce over 700-W average output power in a frequency range from 27.5 GHz to 32.5 GHz, and the corresponding conversion efficiency values vary from 19% to 21.3%, and the maximum output power is 787 W at 30 GHz.

  8. New diagnostics for density measurement on Frascati Tokamak upgrade

    NASA Astrophysics Data System (ADS)

    Tudisco, O.; Canton, A.; Innocente, P.; Mazzotta, C.; Petrov, V. G.; Petrov, A. A.; Avino, F.; Rocchi, G.

    2013-08-01

    In FTU, density profile is measured with two new diagnostics: a CO2/CO scanning interferometer and a time-of-flight radar (denominated refractometer). The first, using two scanning beams, can provide a plasma density profile every 62.5 μs. Two lasers (CO2/CO) are employed for compensation of mechanical vibration of optical components. The scanning component is a small mirror (∅=5 mm) tilting at 8 kHz. The oscillation is cancelled out by a second reflection on this mirror. The time-of- flight refractometer is a two-frequency radar (51.5 GHz and 60.5 GHz) which measures the plasma refractive index from the delay time of an RF pulse that goes through the plasma and is reflected back by the metallic vacuum vessel. The line density and the profile peaking by both diagnostics are in good agreement.

  9. Precipitation retrieval over land and ocean with the SSM/I - Identification and characteristics of the scattering signal

    NASA Technical Reports Server (NTRS)

    Spencer, Roy W.; Hood, Robbie E.; Goodman, H. Michael

    1989-01-01

    Consideration is given to the use of the Defense Meteorological Satellite Program's Special Sensor Microwave/Imager (SSM/I) to identify precipitation in warm and cold land and ocean environments. It is shown that the polarization diversity of the SSM/I operating at 85.5 GHz makes it possible to discriminate between low brightness temperatures due to surface water bodies and those due to precipitation. The theoretical sensitivity of SSM/I between 19.35 and 8.5. GHz and the polarization correction for water surfaces and the effects of cloud water are discussed. Examples are presented of observational studies using SSM/I for the delineation of precipitation over land and oceans.

  10. The Australian experiment with ETS-V

    NASA Technical Reports Server (NTRS)

    Vogel, Wolfhard J.; Goldhirsh, Julius; Hase, Yoshihiro

    1989-01-01

    Land-mobile satellite propagation measurements were implemented at L Band (1.5 GHz) in South-Eastern Australia during an 11 day period in October 1988. Transmissions (CW) from both the Japanese ETS-5 and INMARSAT Pacific geostationary satellites were accessed. Previous measurements in this series were performed at both L Band (1.5 GHz) and UHF (870 MHz) in Central Maryland, North-Central Colorado, and the southern United States. The objectives of the Australian campaign were to expand the data base acquired in the U.S. to another continent, to validate a U.S. derived empirical model for estimating the fade distribution, to establish the effects of directive antennas, to assess the isolation between co- and cross-polarized transmissions, to derive estimates of fade as well as non-fade durations, and to evaluate diversity reception. All these objectives were met.

  11. Performance of exponential coupler in the SPS with LHC type beam for transverse broadband instability analysis

    SciTech Connect

    de Maria,R.; Fox, J. D.; Hofle, W.; Kotzian, G.; Rumolo, G.; Salvant, B.; Wehrle, U.

    2009-05-25

    We present the performance and limitations of the SPS exponential coupler [1] for transverse instability measurements with LHC type beam. Data were acquired in 2008 in the SPS in the time domain with a bandwidth of up to 2.5 GHz. The data were filtered to extract the time evolution of transverse oscillations within the less than 5 ns long LHC type bunches. We describe the data filtering techniques and show the limitations of the pick-up due to propagating modes.

  12. More than 100 channel supercontinuum CW optical source with precise 25GHz spacing for 10Gbit/s DWDM systems

    NASA Astrophysics Data System (ADS)

    Wang, Jianping; Nan, Yinbo; Zhou, Xianwei

    2006-01-01

    We experimentally demonstrate the generation of supercontinuum (SC) with a 12.5GHz DFB/EAM ultrashort optical pulse broadened in the high nonlinear fiber (HNLF). Through longitudinal mode-carving of the SC spectrum, a novel multiwavelength continuous wave (CW) optical source with precise 25GHz channel spacing is realized. The bit error rate (BER) curve and eye diagram show that the multiwavelength CW optical source is promising for dense wavelength division multiplexing (DWDM) systems.

  13. Low-loss LIGA-micromachined conductor-backed coplanar waveguide.

    SciTech Connect

    Forman, Michael A.

    2004-12-01

    A mesoscale low-loss LIGA-micromachined conductor-backed coplanar waveguide is presented. The 517 {micro}m lines are the tallest uniplanar LIGA-fabricated microwave transmission lines to date, as well as the first to be constructed of copper rather than nickel. The conductor-backed micromachined CPW on quartz achieves a measured attenuation of 0.064 dB/cm at 15.5 GHz.

  14. Source counts at 5 gigahertz from the MG survey. [radio astronomy

    NASA Technical Reports Server (NTRS)

    Bennett, C. L.; Lawrence, C. R.; Burke, B. F.

    1985-01-01

    The MIT-Green Bank (MG) radio survey (reported by Bennett and colleagues in 1984 and 1985) is the largest 5 GHz survey to date. In this paper the source counts from the MG survey are examined. They are consistent with past measurements, but due to the large size of the MG survey the Poisson errors have been reduced. Radio source evolution models (such as that reported by Condon in 1984) are consistent with these new measurements.

  15. Superconducting surface impedance under radiofrequency field

    DOE PAGESBeta

    Xiao, Binping P.; Reece, Charles E.; Kelley, Michael J.

    2013-04-26

    Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field. We present the numerical results for Nb and compare these with representative RF field-dependent effective surface resistance measurements from a 1.5 GHz resonant structure.

  16. An All-Optical Microwave Mixer with 8db RF Gain

    NASA Technical Reports Server (NTRS)

    Shieh, W.; Yao, S. X.; Lutes, G.; Maleki, L.

    1997-01-01

    An all-optical microwave mixer with an 8dB RF gain is demonstrated by using a semiconductor optical amplifier (SOA). 6GHz RF signal on a 1312 nm optical carrier is up-converted and down-converted to 1GHZ and 11 GHz by a 5GHz local oscillation (LO) signal on a 1320 nm optical carrier. Such a carrier could readily extend to millimeter wave range.

  17. Tunnel injection transit-time diodes for W-band power generation

    NASA Technical Reports Server (NTRS)

    Kidner, C.; Eisele, H.; Haddad, G. I.

    1992-01-01

    GaAs p(+ +)n(+)n(-)n(+) single-drift tunnel injection transit-time (TUNNETT) diodes for W-band operation have been successfully designed and tested. An output power of 32 mW at 93.5 GHz with a dc to RF conversion efficiency of 2.6 percent was obtained. The oscillations have a clean spectrum in a conventional waveguide cavity.

  18. Electronically tunable fiber laser for optical pumping of {sup 3}He and {sup 4}He

    SciTech Connect

    Stephens, E.F.; Patrick, H.; Gilbert, S.L.

    1996-03-01

    We present in this paper a low threshold, highly stable, integrated fiber laser cavity that uses an electronically tunable internal Bragg grating. The fiber laser produced over 5 mW with a spectral width of about 5 GHz at 1083 nm. The laser was used to achieve 30{percent} polarization of the 2{sup 3}{ital S}{sub 1} metastable states of {sup 4}He in a weak rf discharge cell. {copyright} {ital 1996 American Institute of Physics.}

  19. 78 FR 34309 - Petition for Reconsideration of Action in Rulemaking Proceeding

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-07

    ... to Govern the Use of Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit Space Stations Operating in the 10.95-11.2 GHz, 11.45-11.7 GHz, 11.7-12.2 GHz and 14.0-14.5 GHz Frequency Bands, published at 78 FR 14920, March 8, 2013, and at 78 FR 14952, March 8, 2013, in...

  20. Feasibility Study of Optically Transparent Microstrip Patch Antenna

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1997-01-01

    The paper presents a feasibility study on optically transparent patch antennas with microstrip line and probe feeds. The two antennas operate at 2.3 GHz and 19.5 GHz respectively. They are constructed from a thin sheet of clear polyester with an AgHT-8 optically transparent conductive coating. The experimental results show good radiation patterns and input impedance match. The antennas have potential applications in mobile wireless communications.

  1. EVN detection of Aql X-1 in outburst

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Paragi, Z.; Miller-Jones, J.; Garrett, M.; Fender, R.; Rushton, A.; Spencer, R.

    2009-11-01

    The X-ray binary Aql X-1 has been in outburst in the last few weeks (ATEL #2288, #2296, #2299, #2302, #2303). We observed the system on 2009 November 19 between 14:30-19:00 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The participating radio telescopes were Effelsberg (1 Gbps), Medicina (896 Mbps), Onsala 25m (1 Gbps), Torun (1 Gbps), Westerbork (1 Gbps), Yebes (896 Mbps), and Cambridge (128 Mbps).

  2. The Distance and Mass of the Galaxy Cluster Abell 1995 Derived From Sunyaev-Zel'dovich Effect and X-Ray Measurements

    NASA Technical Reports Server (NTRS)

    Patel, Sandeep K.; Joy, Marshall; Carlstrom, John E.; Holder, Gilbert P.; Reese, Erik D.; Gomez, Percy L.; Hughes, John P.; Grego, Laura; Holzapfel, William L.

    2000-01-01

    We present multi-wavelength observations of the Abell 1995 galaxy cluster. From analysis of x-ray spectroscopy and imaging data we derive the electron temperature, cluster core radius, and central electron number density. Using optical spectroscopy of 15 cluster members, we derive an accurate cluster redshift and velocity dispersion. Finally, the interferometric imaging of the SZE toward Abell 1995 at 28.5 GHz provides a measure of the integrated pressure through the cluster.

  3. Compressive spectrum sensing of radar pulses based on photonic techniques.

    PubMed

    Guo, Qiang; Liang, Yunhua; Chen, Minghua; Chen, Hongwei; Xie, Shizhong

    2015-02-23

    We present a photonic-assisted compressive sampling (CS) system which can acquire about 10(6) radar pulses per second spanning from 500 MHz to 5 GHz with a 520-MHz analog-to-digital converter (ADC). A rectangular pulse, a linear frequency modulated (LFM) pulse and a pulse stream is respectively reconstructed faithfully through this system with a sliding window-based recovery algorithm, demonstrating the feasibility of the proposed photonic-assisted CS system in spectral estimation for radar pulses.

  4. Performance comparison of MSK and QPSK optical long haul DWDM transmission with coherent detection.

    PubMed

    Hachmeister, A; Nölle, M; Molle, L; Freund, R; Rohde, M

    2012-02-13

    We performed long-haul WDM transmission experiments to compare 10 Gbit/s MSK and QPSK modulation with a channel grid of 12.5 GHz. A standard link setup with inline dispersion compensation was applied in combination with coherent detection and following offline signal processing. Both modulation formats showed nearly equal performance bridging about 4000 km at a BER of 10(-3).

  5. Direct modulation of lasers by dispersive threshold switching

    SciTech Connect

    Sartorius, B.; Moehrle, M.

    1996-12-31

    For the first time it is demonstrated, that a laser can be switched electrically on and off at a fixed net gain by a dispersive threshold switching. Switching with 30 dB contrast is achieved by 0.5 mA phase current variation. Short optical pulses were generated by 1 GHz sinus modulation of the phase current. Low chirp was observed at 5 GHz modulation.

  6. The Optical Design of the Background Emission Anisotropy Scanning Telescope (BEAST)

    NASA Astrophysics Data System (ADS)

    Figueiredo, Newton; Bersanelli, Marco; Childers, Jeffery; D'Arcangelo, Ocleto; Halevi, Doron; Janssen, Michael; Kedward, Keith; Lemaster, Nicole; Lubin, Philip; Mandolesi, Nazzareno; Marvil, Joshua; Meinhold, Peter; Mejía, Jorge; Mennella, Aniello; Natoli, Paolo; O'Neil, Hugh; Pina, Agenor; Pryor, Mark; Sandri, Maura; Simonetto, Alessandro; Sozzi, Carlo; Tello, Camilo; Villa, Fabrizio; Villela, Thyrso; Williams, Brian; Wuensche, Carlos Alexandre

    2005-05-01

    We present the optical design of the Background Emission Anisotropy Scanning Telescope (BEAST), an off-axis Gregorian telescope designed to measure the angular distribution of the cosmic microwave background radiation (CMBR) at 30 and 41.5 GHz on angular scales ranging from 20' to 10°. The aperture of the telescope is 1.9 m, and our design meets the strict requirements imposed by the scientific goals of the mission: the beam size is 20' at 41.5 GHz and 26' at 30 GHz, while the illumination at the edge of the mirrors is lower than -30 dB for the central horn. The primary mirror is an off-axis section of a paraboloid, and the secondary an off-axis section of an ellipsoid. A spinning flat mirror located between the sky and the primary provides a two-dimensional chop by rotating the beams around an ellipse on the sky. BEAST uses a receiver array of cryogenic low noise InP High Electron Mobility Transistor (HEMT) amplifiers. The baseline array has seven horns matched to one amplifier each and one horn matched to two amplifiers (two polarizations) for a total of nine amplifiers. Two horns operate around 30 GHz, and six operate around 41.5 GHz. Subsequent campaigns will include 90 GHz and higher frequency channels.

  7. A compact X-Band resonator for DNP-enhanced Fast-Field-Cycling NMR.

    PubMed

    Neudert, Oliver; Mattea, Carlos; Stapf, Siegfried

    2016-10-01

    A new probehead was developed enabling Dynamic Nuclear Polarization (DNP)-enhanced Fast-Field-Cycling relaxometry at 340mT polarization field strength. It is based on a dielectric cavity resonator operating in the TM110 mode at 9.5GHz, which is suitable for both transverse and axial magnet geometries with a bore access of at least 20mm. The probehead includes a planar radio frequency coil for NMR detection and is compatible with standard 3mm NMR tubes. The resonator was assessed in terms of the microwave conversion factor and microwave-induced sample heating effects. Due to the compact size of the cavity, appreciable microwave magnetic field strengths were observed even with only moderate quality factors. Exemplary DNP experiments at 9.5GHz and 2.0GHz microwave frequency are compared for three different viscous samples, demonstrating the advantage of DNP at 9.5GHz for such systems. This new probehead enables new applications of DNP-enhanced Fast-Field-Cycling relaxometry of viscous and solid systems. PMID:27526396

  8. First detection of thermal radio emission from solar-type stars with the Karl G. Jansky very large array

    SciTech Connect

    Villadsen, Jackie; Hallinan, Gregg; Bourke, Stephen; Güdel, Manuel; Rupen, Michael

    2014-06-20

    We present the first detections of thermal radio emission from the atmospheres of solar-type stars τ Cet, η Cas A, and 40 Eri A. These stars all resemble the Sun in age and level of magnetic activity, as indicated by X-ray luminosity and chromospheric emission in Ca II H and K lines. We observed these stars with the Karl G. Jansky Very Large Array with sensitivities of a few μJy at combinations of 10.0, 15.0, and 34.5 GHz. τ Cet, η Cas A, and 40 Eri A are all detected at 34.5 GHz with signal-to-noise ratios of 6.5, 5.2, and 4.5, respectively. 15.0 GHz upper limits imply a rising spectral index greater than 1.0 for τ Cet and 1.6 for η Cas A, at the 95% confidence level. The measured 34.5 GHz flux densities correspond to stellar disk-averaged brightness temperatures of roughly 10,000 K, similar to the solar brightness temperature at the same frequency. We explain this emission as optically thick thermal free-free emission from the chromosphere, with possible contributions from coronal gyroresonance emission above active regions and coronal free-free emission. These and similar quality data on other nearby solar-type stars, when combined with Atacama Large Millimeter/Submillimeter Array observations, will enable the construction of temperature profiles of their chromospheres and lower transition regions.

  9. CONSTRAINTS ON FREE-FREE EMISSION FROM ANOMALOUS MICROWAVE EMISSION SOURCES IN THE PERSEUS MOLECULAR CLOUD

    SciTech Connect

    Tibbs, C. T.; Paladini, R.; Dickinson, C.; Davies, R. D.; Davis, R. J.; Watson, R. A.; Mason, B. S.; Casassus, S.; Cleary, K.

    2013-06-20

    We present observations performed with the Green Bank Telescope at 1.4 and 5 GHz of three strips coincident with the anomalous microwave emission features previously identified in the Perseus molecular cloud at 33 GHz with the Very Small Array. With these observations we determine the level of the low frequency ({approx}1-5 GHz) emission. We do not detect any significant extended emission in these regions and we compute conservative 3{sigma} upper limits on the fraction of free-free emission at 33 GHz of 27%, 12%, and 18% for the three strips, indicating that the level of the emission at 1.4 and 5 GHz cannot account for the emission observed at 33 GHz. Additionally, we find that the low frequency emission is not spatially correlated with the emission observed at 33 GHz. These results indicate that the emission observed in the Perseus molecular cloud at 33 GHz, is indeed in excess over the low frequency emission, hence confirming its anomalous nature.

  10. A compact X-Band resonator for DNP-enhanced Fast-Field-Cycling NMR

    NASA Astrophysics Data System (ADS)

    Neudert, Oliver; Mattea, Carlos; Stapf, Siegfried

    2016-10-01

    A new probehead was developed enabling Dynamic Nuclear Polarization (DNP)-enhanced Fast-Field-Cycling relaxometry at 340 mT polarization field strength. It is based on a dielectric cavity resonator operating in the TM110 mode at 9.5 GHz, which is suitable for both transverse and axial magnet geometries with a bore access of at least 20 mm. The probehead includes a planar radio frequency coil for NMR detection and is compatible with standard 3 mm NMR tubes. The resonator was assessed in terms of the microwave conversion factor and microwave-induced sample heating effects. Due to the compact size of the cavity, appreciable microwave magnetic field strengths were observed even with only moderate quality factors. Exemplary DNP experiments at 9.5 GHz and 2.0 GHz microwave frequency are compared for three different viscous samples, demonstrating the advantage of DNP at 9.5 GHz for such systems. This new probehead enables new applications of DNP-enhanced Fast-Field-Cycling relaxometry of viscous and solid systems.

  11. Constraints on Free-Free Emission from Anomalous Microwave Emission Sources in the Perseus Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Tibbs, C. T.; Paladini, R.; Dickinson, C.; Mason, B. S.; Casassus, S.; Cleary, K.; Davies, R. D.; Davis, R. J.; Watson, R. A.

    2013-06-01

    We present observations performed with the Green Bank Telescope at 1.4 and 5 GHz of three strips coincident with the anomalous microwave emission features previously identified in the Perseus molecular cloud at 33 GHz with the Very Small Array. With these observations we determine the level of the low frequency (~1-5 GHz) emission. We do not detect any significant extended emission in these regions and we compute conservative 3σ upper limits on the fraction of free-free emission at 33 GHz of 27%, 12%, and 18% for the three strips, indicating that the level of the emission at 1.4 and 5 GHz cannot account for the emission observed at 33 GHz. Additionally, we find that the low frequency emission is not spatially correlated with the emission observed at 33 GHz. These results indicate that the emission observed in the Perseus molecular cloud at 33 GHz, is indeed in excess over the low frequency emission, hence confirming its anomalous nature.

  12. AC operation and runaway electron behaviour in HT-7 tokamak

    NASA Astrophysics Data System (ADS)

    Lu, Hong-Wei; Hu, Li-Qun; Zhou, Rui-Jie; Lin, Shi-Yao; Zhong, Guo-Qiang; Wang, Shao-Feng; Chen, Kai-Yun; Xu, Ping; Zhang, Ji-Zong; Ling, Bi-Li; Mao, Song-Tao; Duan, Yan-Min

    2010-06-01

    Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3-1.2 MeV and 0.3-7 MeV, separately. High energy runaway electrons (~MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (~tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.

  13. Initial operation of high power ICRF system for long pulse in EAST

    SciTech Connect

    Qin, C. M. Zhao, Y. P.; Zhang, X. J.; Wan, B. N.; Gong, X. Z.; Mao, Y. Z.; Yuan, S.; Chen, G.

    2015-12-10

    The ICRF heating system on EAST upgraded by active cooling aims for long pulse operation. In this paper, the main technical features of the ICRF system are described. One of a major challenges for long pulse operation is RF-edge interactions induced impurity production and heat loading. In EAST, ICRF antenna protections and Faraday screen bars damaged due to LH electron beam are found. Preliminary results for the analysis of the interaction between LHCD and ICRF antenna are discussed. Increase of metal impurities in the plasma during RF pulse and in a larger core radiation are also shown. These RF-edge interactions at EAST and some preliminary results for the optimizing RF performance will be presented.

  14. Measurement of Fast Electron Transport by Lower Hybrid Modulation Experiments in Alcator C-Mod

    SciTech Connect

    Schmidt, A. E.; Bonoli, P. T.; Parker, R.; Porkolab, M.; Wallace, G.; Wright, J. C.; Wilson, J. R.; Harvey, R. W.; Smirnov, A. P.

    2009-11-26

    The Lower Hybrid Current Drive (LHCD) system on Alcator C-Mod can produce spectra with a wide range of peak parallel refractive index (n{sub parallel}). An experiment in which LH power is square-wave modulated on a time scale much faster than the current relaxation time does not significantly alter the poloidal magnetic field inside the plasma and thus allows for realistic modeling and consistent plasma conditions for different ny spectra. Boxcar binning of hard x-rays during LH power modulation allows for time resolution sufficient to resolve the build-up, steady-state, and slowing-down of fast electrons. A transport model built in Matlab has been used to determine a fast electron pinch velocity for a high-n{sub parallel} case of 1-2 m/s.

  15. Nonlinear lower hybrid modeling in tokamak plasmas

    SciTech Connect

    Napoli, F.; Schettini, G.; Castaldo, C.; Cesario, R.

    2014-02-12

    We present here new results concerning the nonlinear mechanism underlying the observed spectral broadening produced by parametric instabilities occurring at the edge of tokamak plasmas in present day LHCD (lower hybrid current drive) experiments. Low frequency (LF) ion-sound evanescent modes (quasi-modes) are the main parametric decay channel which drives a nonlinear mode coupling of lower hybrid (LH) waves. The spectrum of the LF fluctuations is calculated here considering the beating of the launched LH wave at the radiofrequency (RF) operating line frequency (pump wave) with the noisy background of the RF power generator. This spectrum is calculated in the frame of the kinetic theory, following a perturbative approach. Numerical solutions of the nonlinear LH wave equation show the evolution of the nonlinear mode coupling in condition of a finite depletion of the pump power. The role of the presence of heavy ions in a Deuterium plasma in mitigating the nonlinear effects is analyzed.

  16. Quasilinear analysis of ion Bernstein and lower hybrid waves synergy

    SciTech Connect

    Paoletti, F.; Shoucri, M.; Shkarofsky, A.; Bernabei, S.; Ono, M.

    1996-02-01

    A quasilinear analysis of the absorption of Ion Bernstein Wave (IBW) by the electron population of the plasma is performed. It uses an analytical calculation of the amplitude of the electric field along the trajectory to obtain the quasilinear diffusion coefficient. A numerical integration of the Fokker-Planck equation is performed together with the dynamical evolution of the IBW and Lower Hybrid Wave (LHW) ray trajectories. The damping of IBW is calculated on the distorted distribution function generated by the previous application of Lower Hybrid Current Drive (LHCD) which has bridged the {ital n}{sub {parallel}}-gap. This calculation is particularly relevant because of the IBW/LHW experiments on the Princeton Beta Experiment-Modified (PBX-M). {copyright} {ital 1996 American Institute of Physics.}

  17. Overview of LH operation at JET

    NASA Astrophysics Data System (ADS)

    Kirov, K. K.; Ekedahl, A.; Bernardo, J.; Goniche, M.; Mailloux, J.; Nave, M. F. F.

    2015-12-01

    In this report key aspects of Lower Hybrid Current Drive (LHCD) operation at JET are presented. Amplitude and broadening of the Radio Frequency (RF) spectrum at about 3.7GHz and the frequency shift of the lower sideband were analyzed by means of new diagnostic utilizing RF spectra measurements. Dependencies on plasma density, LH power and the toroidal magnetic field were studied. Plasma rotation profiles with and without LH power were investigated. Power deposition and Current Drive (CD) profiles were assessed by means of a new Ray Tracing / Fokker Planck (RT/FP) code. Significant progress in a number of technological issues including the new supplementary arc protection system based on a visible camera imaging system and operation of the system with waveguides filled with N2 instead of greenhouse SF6 gas was achieved.

  18. High βp plasma formation using off-axis ECCD in Ohmic heated plasma in the spherical tokamak QUEST

    NASA Astrophysics Data System (ADS)

    Mishra, Kishore; Zushi, H.; Idei, H.; Hasegawa, M.; Hanada, K.

    2015-03-01

    High poloidal beta (ɛβp ~ 1) operation in steady state condition in tokamaks is of great interest and has previously been demonstrated using NBI, LHCD and low current (Ip) plasma for a short time (<0.5 s). A very few experiments however, have been performed towards the investigation of highest obtainable βp in tokamak plasma. In this work we report the first result of high βp production and its sustainment though an off axis ECCD at two different frequencies (fundamental and second harmonic) in Ohmic (OH) target plasma. With application of ECCD, plasma βp increased to encounter an equilibrium limit and the standard limiter configuration is transformed to an Inboard Poloidal field Null (IPN) configuration. Both off-axis and on-axis ECCD is studied and found to have some distinctive features, which are discussed in this paper.

  19. Heat transport analysis of the improved confinement discharge with LHW in the HT-7 tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, X. M.; Shen, X.; Wan, B. N.; Wu, Z. W.; Fu, J.; Fu

    2010-04-01

    In the HT-7 tokamak, heat transport analysis is carried out for the lower hybrid current drive (LHCD) experiments. Electrons and ions are coupled and good confinement can be obtained by properly optimizating LHCD and plasma parameters. Under the conditions that the plasma current is about 220 kA, the lower hybrid wave (LHW) power is about 300 kW and the central line-averaged density is about 1.5×1013 cm-3, lower hybrid wave power deposition is off-axis. Local transport analysis illustrated that both electron and ion thermal diffusivities are decreased during the LHW phase, and the electron internal transport barriers (eITBs) are formed while been accompanied by the ion internal transport barriers (iITBs) during LHW phase. Ions are heated by electron-ion collision in the region of the barriers although the ohmic power and the LHW power were absorbed by the electrons. Both electron temperature and ion temperature are increased during the LHW phase, and in the confinement region, the electron-to-ion temperature ratio, Te/Ti varies from 2.0 ~ 2.5 during OH phase to 1.3 ~ 1.6 during LHW injected into the plasma, which shows that electron confinement is not degraded by the electron-ion collisions meanwhile ions are also confined. The energy confinement is increased from 13 ms to 25 ms due to the formation of electron and ion internal transport barries after the LHW is injected into the plasma. LHW driven current and bootstrap current contribute to 60% of the total current.

  20. Analysis of double stub tuner control stability in a many element phased array antenna with strong cross-coupling

    SciTech Connect

    Wallace, G. M.; Fitzgerald, E.; Johnson, D. K.; Kanojia, A. D.; Koert, P.; Lin, Y.; Murray, R.; Shiraiwa, S.; Terry, D. R.; Wukitch, S. J.; Hillairet, J.

    2014-02-12

    Active stub tuning with a fast ferrite tuner (FFT) allows for the system to respond dynamically to changes in the plasma impedance such as during the L-H transition or edge localized modes (ELMs), and has greatly increased the effectiveness of fusion ion cyclotron range of frequency systems. A high power waveguide double-stub tuner is under development for use with the Alcator C-Mod lower hybrid current drive (LHCD) system. Exact impedance matching with a double-stub is possible for a single radiating element under most load conditions, with the reflection coefficient reduced from Γ to Γ{sup 2} in the “forbidden region.” The relative phase shift between adjacent columns of a LHCD antenna is critical for control of the launched n{sub ∥} spectrum. Adding a double-stub tuning network will perturb the phase of the forward wave particularly if the unmatched reflection coefficient is high. This effect can be compensated by adjusting the phase of the low power microwave drive for each klystron amplifier. Cross-coupling of the reflected power between columns of the launcher must also be considered. The problem is simulated by cascading a scattering matrix for the plasma provided by a linear coupling model with the measured launcher scattering matrix and that of the FFTs. The solution is advanced in an iterative manner similar to the time-dependent behavior of the real system. System performance is presented under a range of edge density conditions from under-dense to over-dense and a range of launched n{sub ∥}.

  1. Investigation of lower hybrid physics through power modulation experiments on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Schmidt, A.; Bonoli, P. T.; Meneghini, O.; Parker, R. R.; Porkolab, M.; Shiraiwa, S.; Wallace, G.; Wright, J. C.; Harvey, R. W.; Wilson, J. R.

    2011-05-01

    Lower hybrid current drive (LHCD) is an attractive tool for off-axis current profile control in magnetically confined tokamak plasmas and burning plasmas (ITER), because of its high current drive efficiency. The LHCD system on Alcator C-Mod operates at 4.6 GHz, with ~ 1 MW of coupled power, and can produce a wide range of launched parallel refractive index (n||) spectra. A 32 chord, perpendicularly viewing hard x-ray camera has been used to measure the spatial and energy distribution of fast electrons generated by lower hybrid (LH) waves. Square-wave modulation of LH power on a time scale much faster than the current relaxation time does not significantly alter the poloidal magnetic field inside the plasma and thus allows for realistic modeling and consistent plasma conditions for different n|| spectra. Inverted hard x-ray profiles show clear changes in LH-driven fast electron location with differing n||. Boxcar binning of hard x-rays during LH power modulation allows for ~ 1 ms time resolution which is sufficient to resolve the build-up, steady-state, and slowing-down phases of fast electrons. Ray-tracing/Fokker-Planck modeling in combination with a synthetic hard x-ray diagnostic shows quantitative agreement with the x-ray data for high n|| cases. The time histories of hollow x-ray profiles have been used to measure off-axis fast electron transport in the outer half of the plasma, which is found to be small on a slowing down time scale.

  2. π Scope: python based scientific workbench with visualization tool for MDSplus data

    NASA Astrophysics Data System (ADS)

    Shiraiwa, S.

    2014-10-01

    π Scope is a python based scientific data analysis and visualization tool constructed on wxPython and Matplotlib. Although it is designed to be a generic tool, the primary motivation for developing the new software is 1) to provide an updated tool to browse MDSplus data, with functionalities beyond dwscope and jScope, and 2) to provide a universal foundation to construct interface tools to perform computer simulation and modeling for Alcator C-Mod. It provides many features to visualize MDSplus data during tokamak experiments including overplotting different signals and discharges, various plot types (line, contour, image, etc.), in-panel data analysis using python scripts, and publication quality graphics generation. Additionally, the logic to produce multi-panel plots is designed to be backward compatible with dwscope, enabling smooth migration for dwscope users. πScope uses multi-threading to reduce data transfer latency, and its object-oriented design makes it easy to modify and expand while the open source nature allows portability. A built-in tree data browser allows a user to approach the data structure both from a GUI and a script, enabling relatively complex data analysis workflow to be built quickly. As an example, an IDL-based interface to perform GENRAY/CQL3D simulations was ported on πScope, thus allowing LHCD simulation to be run between-shot using C-Mod experimental profiles. This workflow is being used to generate a large database to develop a LHCD actuator model for the plasma control system. Supported by USDoE Award DE-FC02-99ER54512.

  3. Measurements of the parallel wavenumber of lower hybrid waves in the scrape-off layer of a high-density tokamak

    NASA Astrophysics Data System (ADS)

    Baek, S. G.; Wallace, G. M.; Shinya, T.; Parker, R. R.; Shiraiwa, S.; Bonoli, P. T.; Brunner, D.; Faust, I.; LaBombard, B. L.; Takase, Y.; Wukitch, S.

    2016-05-01

    In lower hybrid current drive (LHCD) experiments on tokamaks, the parallel wavenumber of lower hybrid waves is an important physics parameter that governs the wave propagation and absorption physics. However, this parameter has not been experimentally well-characterized in the present-day high density tokamaks, despite the advances in the wave physics modeling. In this paper, we present the first measurement of the dominant parallel wavenumber of lower hybrid waves in the scrape-off layer (SOL) of the Alcator C-Mod tokamak with an array of magnetic loop probes. The electric field strength measured with the probe in typical C-Mod plasmas is about one-fifth of that of the electric field at the mouth of the grill antenna. The amplitude and phase responses of the measured signals on the applied power spectrum are consistent with the expected wave energy propagation. At higher density, the observed k|| increases for the fixed launched k||, and the wave amplitude decreases rapidly. This decrease is correlated with the loss of LHCD efficiency at high density, suggesting the presence of loss mechanisms. Evidence of the spectral broadening mechanisms is observed in the frequency spectra. However, no clear modifications in the dominant k|| are observed in the spectrally broadened wave components, as compared to the measured k|| at the applied frequency. It could be due to (1) the probe being in the SOL and (2) the limited k|| resolution of the diagnostic. Future experiments are planned to investigate the roles of the observed spectral broadening mechanisms on the LH density limit problem in the strong single pass damping regime.

  4. An assessment of full wave effects on the propagation and absorption of lower hybrid waves

    SciTech Connect

    Wright, J. C.; Bonoli, P. T.; Schmidt, A. E.; Phillips, C. K.; Valeo, E. J.; Harvey, R. W.; Brambilla, M. A.

    2009-07-15

    Lower hybrid (LH) waves ({omega}{sub ci}<<{omega}<<{omega}{sub ce}, where {omega}{sub i,e}{identical_to}Z{sub i,e}eB/m{sub i,e}c) have the attractive property of damping strongly via electron Landau resonance on relatively fast tail electrons and consequently are well-suited to driving current. Established modeling techniques use Wentzel-Kramers-Brillouin (WKB) expansions with self-consistent non-Maxwellian distributions. Higher order WKB expansions have shown some effects on the parallel wave number evolution and consequently on the damping due to diffraction [G. Pereverzev, Nucl. Fusion 32, 1091 (1991)]. A massively parallel version of the TORIC full wave electromagnetic field solver valid in the LH range of frequencies has been developed [J. C. Wright et al., Comm. Comp. Phys. 4, 545 (2008)] and coupled to an electron Fokker-Planck solver CQL3D[R. W. Harvey and M. G. McCoy, in Proceedings of the IAEA Technical Committee Meeting, Montreal, 1992 (IAEA Institute of Physics Publishing, Vienna, 1993), USDOC/NTIS Document No. DE93002962, pp. 489-526] in order to self-consistently evolve nonthermal electron distributions characteristic of LH current drive (LHCD) experiments in devices such as Alcator C-Mod and ITER (B{sub 0}{approx_equal}5 T, n{sub e0}{approx_equal}1x10{sup 20} m{sup -3}). These simulations represent the first ever self-consistent simulations of LHCD utilizing both a full wave and Fokker-Planck calculation in toroidal geometry.

  5. Assessment of the LH wave for demo in pulsed and steady state scenario

    SciTech Connect

    Cardinali, A.; Barbato, E.; Castaldo, C.; Cesario, R.; Marinucci, M.; Ravera, G. L.; Tuccillo, A. A.; Ceccuzzi, S.; Mirizzi, F.; Panaccione, L.; Santini, F.; Schettini, G.

    2014-02-12

    The Lower Hybrid Current Drive (LHCD) has been analysed in DEMO tokamak plasma in the 'pulsed and steady state regime' considering two plasma scenarios characterized, respectively, by flat density profile and peaked density profiles. We have obtained LH deposition profiles in cases of neglecting the effect of spectral broadening produced by PI at the edge. By comparing the Power Deposition Profiles for both DEMO scenarios ('flat' and 'peaked'), the SOL of DEMO does not play any role in the absorption of the LH wave. In all cases the deposition is localized inside the separatrix layer r/a≤1. By lowering the parallel wave-number peak of the power spectrum from 1.8 to 1.5, the accessibility condition in both case prevents the power from reaching the deposition layer apart from a small fraction which pertains to the higher n∥ of the power spectrum. The spectrum centred at 1.8 is suggested to be useful in DEMO. More realistically, as supported by available data of LHCD in a wide range of operating densities, the effect of parametric decay instability (PDI) can produce a spectral broadening which should be included in the simulations. Further studies would be necessary for assessing the temperature profiles in the SOL at reactor-graded conditions. This is because, if the SOL temperature is at least of the order of 50 to 100 eV, the effect of PDI broads the spectrum up to n∥≤10, and the deposition profile is slightly wider but not much shifted outwards.

  6. Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Faust, I. C.; Brunner, D.; LaBombard, B.; Parker, R. R.; Terry, J. L.; Whyte, D. G.; Baek, S. G.; Edlund, E.; Hubbard, A. E.; Hughes, J. W.; Kuang, A. Q.; Reinke, M. L.; Shiraiwa, S.; Wallace, G. M.; Walk, J. R.

    2016-05-01

    For the first time, the power deposition of lower hybrid RF waves into the edge plasma of a diverted tokamak has been systematically quantified. Edge deposition represents a parasitic loss of power that can greatly impact the use and efficiency of Lower Hybrid Current Drive (LHCD) at reactor-relevant densities. Through the use of a unique set of fast time resolution edge diagnostics, including innovative fast-thermocouples, an extensive set of Langmuir probes, and a Lyα ionization camera, the toroidal, poloidal, and radial structure of the power deposition has been simultaneously determined. Power modulation was used to directly isolate the RF effects due to the prompt ( t < τ E ) response of the scrape-off-layer (SOL) plasma to Lower Hybrid Radiofrequency (LHRF) power. LHRF power was found to absorb more strongly in the edge at higher densities. It is found that a majority of this edge-deposited power is promptly conducted to the divertor. This correlates with the loss of current drive efficiency at high density previously observed on Alcator C-Mod, and displaying characteristics that contrast with the local RF edge absorption seen on other tokamaks. Measurements of ionization in the active divertor show dramatic changes due to LHRF power, implying that divertor region can be a key for the LHRF edge power deposition physics. These observations support the existence of a loss mechanism near the edge for LHRF at high density ( n e > 1.0 × 10 20 (m-3)). Results will be shown addressing the distribution of power within the SOL, including the toroidal symmetry and radial distribution. These characteristics are important for deducing the cause of the reduced LHCD efficiency at high density and motivate the tailoring of wave propagation to minimize SOL interaction, for example, through the use of high-field-side launch.

  7. Magnetic cycles of Sun-like stars with different levels of coronal and chromospheric activity — comparison with the Sun

    NASA Astrophysics Data System (ADS)

    Shimanovskaya, Elena; Bruevich, Vasiliy; Bruevich, Elena

    2016-09-01

    The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of F, G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycle, is different: it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of chromospheric and coronal activity confirms that the Sun belongs to stars with a low level of chromospheric activity and stands apart among these stars by its minimum level of coronal radiation and minimum level of variations in photospheric flux.

  8. Exclusive channels in semi-inclusive production of pions and kaons

    SciTech Connect

    Markus Diehl; Wolfgang Kugler; Andreas Schaefer; Christian Weiss

    2005-06-01

    We investigate the role of exclusive channels in semi-inclusive electroproduction of pions and kaons. Using the QCD factorization theorem for hard exclusive processes we evaluate the cross sections for exclusive pseudoscalar and vector meson production in terms of generalized parton distributions and meson distribution amplitudes. We investigate the uncertainties arising from the modeling of the nonperturbative input quantities. Combining these results with available experimental data, we compare the cross sections for exclusive channels to that obtained from quark fragmentation in semi-inclusive deep inelastic scattering. We find that rho0 production is the only exclusive channel with significant contributions to semi-inclusive pion production at large z and moderate Q2. The corresponding contribution to kaon production from the decay of exclusively produced phi and Kstar is rather small.

  9. Electron Cyclotron Emission Imaging on ITER with Rowland Circle Optics

    NASA Astrophysics Data System (ADS)

    Liu, Jason; Lee, Woochang; Leem, June-Eok; Bitter, Manfred; Park, Hyeon; Yun, Gunsu

    2015-11-01

    The implementation of advanced electron cyclotron emission imaging (ECEI) systems on the major tokamaks TEXTOR1, DIII-D2,3, KSTAR4, EAST5, and ASDEX Upgrade6 has revolutionized the diagnosis of MHD activities and improved our understanding of various instabilities. However, the conventional ECEI systems cannot be applied to ITER because of the space constraints and excessive radiation that would be encountered in the diagnostic port plugs. This paper describes an alternative optical concept that employs the Rowland circle imaging geometry to implement an advanced ECEI system on ITER that is suitable for the tight space and harsh environments of the diagnostic port plugs. Such a system would match the capabilities of conventional ECEI diagnostics and would be capable of simultaneous core and edge measurements.

  10. Reliability of the two-point measurement of the spatial correlation length from Gaussian-shaped fluctuating signals in fusion-grade plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Jaewook; Nam, Y. U.; Lampert, M.; Ghim, Y.-C.

    2016-10-01

    A statistical method for the estimation of the spatial correlation lengths of Gaussian-shaped fluctuating signals with two measurement points is examined to quantitatively evaluate its reliability (variance) and accuracy (bias error). The standard deviation of the correlation value is analytically derived for randomly distributed Gaussian shaped fluctuations satisfying stationarity and homogeneity, allowing us to evaluate, as a function of fluctuation-to-noise ratios, the sizes of averaging time windows and the ratios of the distance between the two measurement points to the true correlation length, and the goodness of the two-point measurement for estimating the spatial correlation length. Analytic results are confirmed with numerically generated synthetic data and real experimental data obtained with the KSTAR beam emission spectroscopy diagnostic. Our results can be applied to Gaussian-shaped fluctuating signals where a correlation length must be measured with only two measurement points.

  11. Quantitative measurement of in-vessel dust velocity and its correlation with toroidal rotation of plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Suk-Ho; Kim, Kyung-Rae; Ko, Won-Ha; Nam, YongUn

    2015-08-01

    In-vessel dust velocity and its distribution have been evaluated by using dedicated software developed at KSTAR. The dust velocities are well described by log-normal distribution function in a range from ∼10 m/s up to ∼460 m/s. The peak velocity of the distribution increases through three campaigns from 2010 to 2012, mainly due to the increase of the input energy level. From the force balance, it is expected that the dust velocity is strongly correlated with the toroidal plasma flow due to the ion drag force acting on dusts. To confirm this, toroidal rotation velocity is measured by using charge exchange spectroscopy (CES) as a function of normalized stored energy (W/Ip), which is similar with Rice scaling. As a consequence, it is found that the dust velocity is linearly proportional to W/Ip, thus to the toroidal rotation velocity of the plasmas.

  12. Diagnostics and required R and D for control of DEMO grade plasmas

    SciTech Connect

    Park, Hyeon K.

    2014-08-21

    Even if the diagnostics of ITER performs as expected, installation and operation of the diagnostic systems in Demo device will be much harsher than those of the present ITER device. In order to operate the Demo grade plasmas, which may have a higher beta limit, safely with very limited number of simple diagnostic system, it requires a well defined predictable plasma modelling in conjunction with the reliable control system for burn control and potential harmful instabilities. Development of such modelling in ITER is too risky and the logical choice would be utilization of the present day steady state capable devices such as KSTAR and EAST. In order to fulfill this mission, sophisticated diagnostic systems such as 2D/3D imaging systems can validate the physics in the theoretical modeling and challenge the predictable capability.

  13. Three-dimensional modeling of beam emission spectroscopy measurements in fusion plasmas

    SciTech Connect

    Guszejnov, D.; Pokol, G. I.; Pusztai, I.; Refy, D.; Zoletnik, S.; Lampert, M.; Nam, Y. U.

    2012-11-15

    One of the main diagnostic tools for measuring electron density profiles and the characteristics of long wavelength turbulent wave structures in fusion plasmas is beam emission spectroscopy (BES). The increasing number of BES systems necessitated an accurate and comprehensive simulation of BES diagnostics, which in turn motivated the development of the Rate Equations for Neutral Alkali-beam TEchnique (RENATE) simulation code that is the topic of this paper. RENATE is a modular, fully three-dimensional code incorporating all key features of BES systems from the atomic physics to the observation, including an advanced modeling of the optics. Thus RENATE can be used both in the interpretation of measured signals and the development of new BES systems. The most important components of the code have been successfully benchmarked against other simulation codes. The primary results have been validated against experimental data from the KSTAR tokamak.

  14. Three-dimensional modeling of beam emission spectroscopy measurements in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Guszejnov, D.; Pokol, G. I.; Pusztai, I.; Refy, D.; Zoletnik, S.; Lampert, M.; Nam, Y. U.

    2012-11-01

    One of the main diagnostic tools for measuring electron density profiles and the characteristics of long wavelength turbulent wave structures in fusion plasmas is beam emission spectroscopy (BES). The increasing number of BES systems necessitated an accurate and comprehensive simulation of BES diagnostics, which in turn motivated the development of the Rate Equations for Neutral Alkali-beam TEchnique (RENATE) simulation code that is the topic of this paper. RENATE is a modular, fully three-dimensional code incorporating all key features of BES systems from the atomic physics to the observation, including an advanced modeling of the optics. Thus RENATE can be used both in the interpretation of measured signals and the development of new BES systems. The most important components of the code have been successfully benchmarked against other simulation codes. The primary results have been validated against experimental data from the KSTAR tokamak.

  15. CRYOGENICS FOR FUSION

    SciTech Connect

    Dauguet, P.; Bonneton, M.; Fauve, E.; Bernhardt, J. M.; Beauvisage, J.; Andrieu, F.; Gistau-Baguer, G. M.; Boissin, J. C.

    2008-03-16

    Fusion of Hydrogen to produce energy is one of the technologies under study to meet the mankind raising need in energy and as a substitute to fossil fuels for the future. This technology is under investigation for more than 30 years already, with, for example, the former construction of the experimental reactors Tore Supra, DIII-D and JET. With the construction of ITER to start, the next step to 'fusion for energy' will be done. In these projects, an extensive use of cryogenic systems is requested. Air Liquide has been involved as cryogenic partner in most of former and presently constructed fusion reactors. In the present paper, a review of the cryogenic systems we delivered to Tore Supra, JET, IPR and KSTAR will be presented.

  16. Three-dimensional modeling of beam emission spectroscopy measurements in fusion plasmas.

    PubMed

    Guszejnov, D; Pokol, G I; Pusztai, I; Refy, D; Zoletnik, S; Lampert, M; Nam, Y U

    2012-11-01

    One of the main diagnostic tools for measuring electron density profiles and the characteristics of long wavelength turbulent wave structures in fusion plasmas is beam emission spectroscopy (BES). The increasing number of BES systems necessitated an accurate and comprehensive simulation of BES diagnostics, which in turn motivated the development of the Rate Equations for Neutral Alkali-beam TEchnique (RENATE) simulation code that is the topic of this paper. RENATE is a modular, fully three-dimensional code incorporating all key features of BES systems from the atomic physics to the observation, including an advanced modeling of the optics. Thus RENATE can be used both in the interpretation of measured signals and the development of new BES systems. The most important components of the code have been successfully benchmarked against other simulation codes. The primary results have been validated against experimental data from the KSTAR tokamak.

  17. Arc plasma simulation of the KAERI large ion sourcea)

    NASA Astrophysics Data System (ADS)

    In, S. R.; Jeong, S. H.; Kim, T. S.

    2008-02-01

    The KAERI large ion source, developed for the KSTAR NBI system, recently produced ion beams of 100keV, 50A levels in the first half campaign of 2007. These results seem to be the best performance of the present ion source at a maximum available input power of 145kW. A slight improvement in the ion source is certainly necessary to attain the final goal of an 8MW ion beam. Firstly, the experimental results were analyzed to differentiate the cause and effect for the insufficient beam currents. Secondly, a zero dimensional simulation was carried out on the ion source plasma to identify which factors control the arc plasma and to find out what improvements can be expected.

  18. Fluid-particle hybrid simulation on the transports of plasma, recycling neutrals, and carbon impurities in the Korea Superconducting Tokamak Advanced Research divertor region

    NASA Astrophysics Data System (ADS)

    Kim, Deok-Kyu; Hong, Sang Hee

    2005-06-01

    A two-dimensional simulation modeling that has been performed in a self-consistent way for analysis on the fully coupled transports of plasma, recycling neutrals, and intrinsic carbon impurities in the divertor domain of tokamaks is presented. The numerical model coupling the three major species transports in the tokamak edge is based on a fluid-particle hybrid approach where the plasma is described as a single magnetohydrodynamic fluid while the neutrals and impurities are treated as kinetic particles using the Monte Carlo technique. This simulation code is applied to the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak [G. S. Lee, J. Kim, S. M. Hwang et al., Nucl. Fusion 40, 575 (2000)] to calculate the peak heat flux on the divertor plate and to explore the divertor plasma behavior depending on the upstream conditions in its base line operation mode for various values of input heating power and separatrix plasma density. The numerical modeling for the KSTAR tokamak shows that its full-powered operation is subject to the peak heat loads on the divertor plate exceeding an engineering limit, and reveals that the recycling zone is formed in front of the divertor by increasing plasma density and by reducing power flow into the scrape-off layer. Compared with other researchers' work, the present hybrid simulation more rigorously reproduces severe electron pressure losses along field lines by the presence of recycling zone accounting for the transitions between the sheath limited and the detached divertor regimes. The substantial profile changes in carbon impurity population and ionic composition also represent the key features of this divertor regime transition.

  19. Advanced on-chip divider for monolithic microwave VCO's

    NASA Technical Reports Server (NTRS)

    Peterson, Weddell C.

    1989-01-01

    High frequency division on a monolithic circuit is a critical technology required to significantly enhance the performance of microwave and millimeter-wave phase-locked sources. The approach used to meet this need is to apply circuit design practices which are essentially 'microwave' in nature to the basically 'digital' problem of high speed division. Following investigation of several promising circuit approaches, program phase 1 culminated in the design and layout of an 8.5 GHz (Deep Space Channel 14) divide by four circuit based on a dynamic mixing divider circuit approach. Therefore, during program phase 2, an 8.5 GHz VCO with an integral divider which provides a phase coherent 2.125 GHz reference signal for phase locking applications was fabricated and optimized. Complete phase locked operation of the monolithic GaAs devices (VCO, power splitter, and dynamic divider) was demonstrated both individually and as an integrated unit. The fully functional integrated unit in a suitable test fixture was delivered to NASA for engineering data correlation. Based on the experience gained from this 8.5 GHz super component, a monolithic GaAs millimeter-wave dynamic divider for operation with an external VCO was also designed, fabricated, and characterized. This circuit, which was also delivered to NASA, demonstrated coherent division by four at an input frequency of 24.3 GHz. The high performance monolithic microwave VCO with a coherent low frequency reference output described in this report and others based on this technology will greatly benefit advanced communications systems in both the DoD and commercial sectors. Signal processing and instrumentation systems based on phase-locking loops will also attain enhanced performance at potentially reduced cost.

  20. 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.

  1. Anomalous variation in the wireless signals propagation associated with earthquake preparation processes

    NASA Astrophysics Data System (ADS)

    Ouzounov, Dimitar; Velichkova-Yotsova, Sylvia; Pulinets, Sergey

    2016-04-01

    propagation correlated with earthquake preparation processes. Our observations revealed a phenomena associated with the artificially enhancement of the intensity 3.5GHz signals by using WiMax technology (no change in the transmitting level) as a result of electric and electrochemical processes in atmosphere over the regions of ongoing earthquake preparation. To illustrate the nature of such variations in the range of 3.5GHz in relation to earthquake processes we present two case studies: 1/ for M5.8 of May 22, 2012 in Bulgaria and 2/ for M6.9 of May 24, 2014 in Aegean Sea. Concerning the M5.8 of May 22, 2012 the abnormal intensity modulation started on 05.17.2012 (five days in advance) and reached 200% increase. Epicenter of the M5.8 of May 25 was on 15 km from the wireless receiver. Concerning and M6.9 of May 24, 2014 in Aegean Sea abnormal signal was observed on May 22 (two days in advance) with 30% intensity increase. Epicenter of M6.9 of May 24 was at 260 km from the wireless receiver. Most likely the observed increase in the intensity is a direct result of the change in the atmospheric properties in the Atmospheric boundary level (ABL) triggered by intensification of radon and other gases release, which lead to change in lowers atmosphere conductivity, already suggested by Lithosphere-Atmosphere-Ionosphere Coupling concept (Pulinets and Ouzounov, 2011). Another possible reason is the forward scattering of WiMax signal (similar to meteor wakes scattering) on aerosol layers formed over the earthquake preparation zone. We are registering an effect of systematic increase (with different rate) at 3.5 GHz associated with the regional seismicity and no significant intensify modulation with an absence of major seismicity in the region.

  2. Olympus propagation studies in the US: Receiver development and the data acquisition system

    NASA Technical Reports Server (NTRS)

    Mckeeman, John C.

    1990-01-01

    Virginia Tech has developed two types of receivers to monitor the Olympus beacons, as well as a custom data acquisition system to store and display propagation data. Each of the receiver designs uses new hybrid analog/digital techniques. The data acquisition system uses a stand alone processor to collect and format the data for display and subsequent processing. The launch of the Olympus satellite with its coherent beacons offers new opportunities to study propagation effects at 12.5, 20, and 30 GHz. At Virginia Tech, the satellite is at 14 degrees in elevation, which allows us to measure low elevation angle effects. However, to make these measurements, a very accurate and stable measurement system is required. Virginia Tech has constructed a complex receiving system which monitors the Olympus beacons and all parameters associated with propagation research. In the current configuration, researchers have developed a receiver which frequency locks to the less fade susceptible 12.5 GHz beacon. Since all beacons on the satellite are driven from a single master oscillator, drift in the 12.5 GHz beacon implies corresponding drifts in the 20, and 30 GHz beacons. The receivers for the 20 and 30 GHz systems derive their frequency locking information from the 12.5 GHz system. This widens the dynamic range of the receivers and allows the receivers to maintain lock in severe fade conditions. In addition to monitoring the beacons, the sky noise is monitored with radiometers at each frequency. The radiometer output is used to set the clear air level for each beacon measurement. Researchers also measure the rain rate with several tipping bucket rain gauges placed along the propagation path.

  3. VLBA AND CHANDRA OBSERVATIONS OF JETS IN FRI RADIO GALAXIES: CONSTRAINTS ON JET EVOLUTION

    SciTech Connect

    Kharb, P.; O'Dea, C. P.; Tilak, A.; Baum, S. A.; Haynes, E.; Noel-Storr, J.; Fallon, C.; Christiansen, K.

    2012-07-20

    We present here the results from new Very Long Baseline Array (VLBA) observations at 1.6 and 5 GHz of 19 galaxies of a complete sample of 21 Uppasala General Catalog (UGC) Fanaroff-Riley type I (FRI) radio galaxies. New Chandra data of two sources, viz., UGC 00408 and UGC 08433, are combined with the Chandra archival data of 13 sources. The 5 GHz observations of 10 'core-jet' sources are polarization-sensitive, while the 1.6 GHz observations constitute second-epoch total intensity observations of nine 'core-only' sources. Polarized emission is detected in the jets of seven sources at 5 GHz, but the cores are essentially unpolarized, except in M87. Polarization is detected at the jet edges in several sources, and the inferred magnetic field is primarily aligned with the jet direction. This could be indicative of magnetic field 'shearing' due to jet-medium interaction, or the presence of helical magnetic fields. The jet peak intensity I{sub {nu}} falls with distance d from the core, following the relation, I{sub {nu}}{proportional_to}d{sup a} , where a is typically {approx} - 1.5. Assuming that adiabatic expansion losses are primarily responsible for the jet intensity 'dimming,' two limiting cases are considered: (1) the jet has a constant speed on parsec scales and is expanding gradually such that the jet radius r{proportional_to}d 0{sup .4}; this expansion is, however, unobservable in the laterally unresolved jets at 5 GHz, and (2) the jet is cylindrical and is accelerating on parsec scales. Accelerating parsec-scale jets are consistent with the phenomenon of 'magnetic driving' in Poynting-flux-dominated jets. While slow jet expansion as predicted by case (1) is indeed observed in a few sources from the literature that are resolved laterally, on scales of tens or hundreds of parsecs, case (2) cannot be ruled out in the present data, provided the jets become conical on scales larger than those probed by VLBA. Chandra observations of 15 UGC FRIs detect X-ray jets in

  4. Land mobile satellite propagation measurements in Japan using ETS-V satellite

    NASA Technical Reports Server (NTRS)

    Obara, Noriaki; Tanaka, Kenji; Yamamoto, Shin-Ichi; Wakana, Hiromitsu

    1993-01-01

    Propagation characteristics of land mobile satellite communications channels have been investigated actively in recent years. Information of propagation characteristics associated with multipath fading and shadowing is required to design commercial land mobile satellite communications systems, including protocol and error correction method. CRL (Communications Research Laboratory) has carried out propagation measurements using the Engineering Test Satellite-V (ETS-V) at L band (1.5 GHz) through main roads in Japan by a medium gain antenna with an autotracking capability. This paper presents the propagation statistics obtained in this campaign.

  5. Exploring the conformational landscape of menthol, menthone, and isomenthone: a microwave study.

    PubMed

    Schmitz, David; Shubert, V Alvin; Betz, Thomas; Schnell, Melanie

    2015-01-01

    The rotational spectra of the monoterpenoids menthol, menthone, and isomenthone are reported in the frequency range of 2-8.5 GHz, obtained with broadband Fourier-transform microwave spectroscopy. For menthol only one conformation was identified under the cold conditions of the molecular jet, whereas three conformations were observed for menthone and one for isomenthone. The conformational space of the different molecules was extensively studied using quantum chemical calculations, and the results were compared with molecular parameters obtained by the measurements. Finally, a computer program is presented, which automatically identifies different species in a dense broadband microwave spectrum using calculated ab initio rotational constants as initial input parameters.

  6. Fade-durations derived from land-mobile-satellite measurements in Australia

    NASA Technical Reports Server (NTRS)

    Hase, Yoshihiro; Vogel, Wolfhard J.; Goldhirsh, Julius

    1991-01-01

    Transmissions from the Japanese ETS-V geostationary satellite were measured at L band (1.5 GHz) in a vehicle driving on roads of southeastern Australia. The measurements were part of a program designed to characterize propagation effects due to roadside trees and terrain for mobile satellite service. It is shown that the cumulative distributions of fade and nonfade durations follow a lognormal and power law, respectively. At 1 percent probability, fades last 2-8 m, and nonfades 10-100 m, depending on the degree of shadowing. Phase fluctuations are generally small, allowing the channel characteristics to be estimated from levels only.

  7. Preparation of a primary argon beam for the CERN fixed target physics

    SciTech Connect

    Küchler, D. O’Neil, M.; Scrivens, R.; Thomae, R.

    2014-02-15

    The fixed target experiment NA61 in the North Area of the Super Proton Synchrotron is studying phase transitions in strongly interacting matter. Up to now they used the primary beams available from the CERN accelerator complex (protons and lead ions) or fragmented beams created from the primary lead ion beam. To explore a wider range of energies and densities a request was made to provide primary argon and xenon beams. This paper describes the results of the setting up and 10 week test run of the Ar{sup 11+} beam from the 14.5 GHz ECR ion source and the linear accelerator (Linac3) at CERN.

  8. Design of nonradiative dielectric waveguide filters

    NASA Astrophysics Data System (ADS)

    Yoneyama, T.; Kuroki, F.; Nishida, S.

    1984-12-01

    An efficient design technique of nonradiative dielectric waveguide filters for use at millimeter wavelengths is developed. Filter structures considered here are a gap-coupled type and an alternating-width type. According to present theory, 3-pole, 0.1-dB Chebyshev ripple bandpass filters with a 2-percent bandwidth at a center frequency of 49.5 GHz were designed and fabricated with Teflon dielectric. Calculated and measured filter responses agree quite well, and excess insertion losses are found to be as small as 0.3 dB for both types of the fabricated filter circuits.

  9. Preparation of a primary argon beam for the CERN fixed target physics.

    PubMed

    Küchler, D; O'Neil, M; Scrivens, R; Thomae, R

    2014-02-01

    The fixed target experiment NA61 in the North Area of the Super Proton Synchrotron is studying phase transitions in strongly interacting matter. Up to now they used the primary beams available from the CERN accelerator complex (protons and lead ions) or fragmented beams created from the primary lead ion beam. To explore a wider range of energies and densities a request was made to provide primary argon and xenon beams. This paper describes the results of the setting up and 10 week test run of the Ar(11+) beam from the 14.5 GHz ECR ion source and the linear accelerator (Linac3) at CERN.

  10. Ultra-stable Hg(+) trapped ion frequency standard

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Dick, G. John; Maleki, Lute

    1990-01-01

    A fieldable trapped ion frequency standard based on Hg-199(+) ions confined in a hybrid rf/dc linear ion trap is developed. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the rf confining fields. In preliminary measurements a stability of 2 to 3 x 10(exp -15) was obtained for 10000 second averaging times. These measurements were carried out with a 120 mHz wide atomic resonance line for the 40.5 GHz clock transition with a second order Doppler shift from the rf trapping field of 6 x 10(exp -13).

  11. High-power Ka-band amplifier

    NASA Technical Reports Server (NTRS)

    Cormier, R.

    1993-01-01

    Development of a high-power tube suitable to power a Ka-band (34.5-GHz) antenna transmitter located at the Goldstone, California, tracking station is continuing. The University of Maryland Laboratory for Plasma Research and JPL are conducting a joint effort to test the feasibility of phase locking a second-harmonic gyrotron both by direct injection at the output cavity and by using a priming cavity to bunch the electrons in the beam. This article describes several design options and the results of computer simulation testing.

  12. W-band OFDM Radio-over-Fiber system with power detector for vector signal down-conversion.

    PubMed

    Lin, Chun-Ting; Wu, Meng-Fan; Ho, Chun-Hung; Li, Che-Hao; Lin, Chi-Hsiang; Huang, Hou-Tzu

    2015-06-01

    This Letter proposes a W-band OFDM RoF system at 103.5 GHz employing power detector to support vector signal down-conversion. Additional RF tone is generated and transmitted from central office to replace the local oscillator at a wireless receiver. With a proper frequency gap and power ratio between the RF tone and the OFDM-modulated signal, the impact from signal-to-signal beating interference can be minimized. The data rate can achieve a 40 Gbps 16 QAM OFDM signal over 25 km fiber and 2 m wireless transmission. PMID:26030536

  13. A system for traceable measurement of the microwave complex permittivity of liquids at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Dimitrakis, G A; George, M; Poliakoff, M; Harrison, I; Robinson, J; Kingman, S; Lester, E; Gregory, A P; Lees, K

    2009-04-01

    A system has been developed for direct traceable dielectric measurements on liquids at high pressures and temperatures. The system consists of a coaxial reflectometric sensor terminated by a metallic cylindrical cell to contain the liquid. It has been designed for measurements on supercritical liquids, but as a first step measurements on dielectric reference liquids were performed. This paper reports on a full evaluation of the system up to 2.5 GHz using methanol, ethanol and n-propanol at pressures up to 9 MPa and temperatures up to 273 °C. A comprehensive approach to the evaluation of uncertainties using Monte Carlo modelling is used.

  14. Simultaneous observations of hard X-ray and microwave burst sources in a limb flare

    NASA Technical Reports Server (NTRS)

    Takakura, T.; Kundu, M. R.; Mcconnell, D.; Ohki, K.

    1985-01-01

    Observations of a flare which occurred just behind the west solar limb on 1981 August 3 are reported. A hard X-ray source (20-30 keV) and a microwave source at 5 GHz were observed simultaneously using the Very Large Array and the hard X-ray telescope aboard the Hinotori spacecraft. Both sources were located in the corona, apparently near the tops of two independent coronal arcades or loops. The source may be composed of many thin filaments unresolved by the VLA observations.

  15. Generation of constant-amplitude radio-frequency sweeps at a tunnel junction for spin resonance STM

    NASA Astrophysics Data System (ADS)

    Paul, William; Baumann, Susanne; Lutz, Christopher P.; Heinrich, Andreas J.

    2016-07-01

    We describe the measurement and successful compensation of the radio-frequency transfer function of a scanning tunneling microscope over a wide frequency range (15.5-35.5 GHz) and with high dynamic range (>50 dB). The precise compensation of cabling resonances and attenuations is critical for the production of constant-voltage frequency sweeps for electric-field driven electron spin resonance (ESR) experiments. We also demonstrate that a well-calibrated tunnel junction voltage is necessary to avoid spurious ESR peaks that can arise due to a non-flat transfer function.

  16. Results of an intercomparison for free space antenna factor measurements within the German Calibration Service (DKD)

    NASA Astrophysics Data System (ADS)

    Kleine-Ostmann, Thomas; Huncke, Frank; Schwarzbeck, Dieter; Martetschläger, Otto; Gaßner, Jürgen; Guserle, Andreas; Römer, Christian; Hufnagel, Thomas; Lehmann, Mario; Karsten, Uwe; Schrader, Thorsten

    2016-09-01

    In this paper we discuss the results of an intercomparison for free space antenna factor measurements performed within the German Calibration Service (DKD). Three different types of antennas covering the frequency range from 30 MHz to 26.5 GHz have been calibrated in five different laboratories using different methods and calibration sites to obtain the free space antenna factor. The results agree well within the uncertainties specified by the laboratories suggesting that different approaches and different measurement sites to obtain the free space antenna factor are well compatible.

  17. Strategic considerations in SETI, and a microwave approach. [Search for ExtraTerrestrial Intelligence

    NASA Technical Reports Server (NTRS)

    Seeger, C. L.

    1977-01-01

    Plausible options in the search for extraterrestrial intelligence (SETI), and the need to reserve a suitable portion of the EM (microwave) spectrum for SETI research, are discussed. Reasons for selection of a portion of the spectrum, specifically the 'water hole' near 1.5 GHz in the terrestrial microwave window (1-25 GHz), are presented, and competition with various emitters for that band (existing satellite downlink transmissions) is discussed. SETI search policies and options are summarized in a table. Speculative considerations guiding initial phases of the SETI pursuit are discussed.

  18. First operation of a dielectric-loaded double-stripline free-electron maser experiment

    SciTech Connect

    Einat, M.; Jerby, E.; Shahadi, A.

    1995-12-31

    A tabletop free-electron maser (FEM) experiment based on a dielectric-loaded double-stripline waveguide is presented. It employs a low-energy (8 keV, 0.5 A) electron beam and a folded-foil wiggler ({lambda}w = 2 cm). Metal striplines protects the dielectric slabs from the electron beam and support quasi-TEM modes in the waveguide. Radiation output is observed at f = 3.5 GHz, in agreement with the dielectric-loaded FEM tuning relation.

  19. Ringing in the pulse response of long and wideband coaxial transmission lines due to group delay dispersion

    SciTech Connect

    Kotzian,G.; de Maria,R.; Caspers, F.; Federmann, S.; Hofle, W.

    2009-05-04

    In particle accelerators coaxial cables are commonly used to transmit wideband beam signals covering many decades of frequencies over long distances. Those transmission lines often have a corrugated outer and/or inner conductor. This particular construction exhibits a significant amount of frequency dependent group delay variation. A comparison of simulations based on theoretical models, numerical simulations and S{sub 21} network analyzer measurements up to 2.5 GHz is presented. It is shown how the non-linear phase response and varying group delay leads to ringing in the pulse response and subsequent distortion of signal s transmitted through such coaxial transmission lines.

  20. Generation of FCC-compliant and background-free millimeter-wave ultrawideband signal based on nonlinear polarization rotation in a highly nonlinear fiber.

    PubMed

    Li, Wei; Wang, Wen Ting; Sun, Wen Hui; Liu, Jian Guo; Zhu, Ning Hua

    2014-05-01

    We propose a novel approach to generating millimeter-wave (MMW) ultrawideband (UWB) signal based on nonlinear polarization rotation (NPR) in a highly nonlinear fiber (HNLF). The MMW UWB signal is background-free by eliminating the baseband frequency components using an optical filter. The proposed scheme is theoretically analyzed and experimentally verified. The generated MMW UWB signal centered at 25.5 GHz has a 10-dB bandwidth of 7 GHz from 22 to 29 GHz, which fully satisfies the spectral mask regulated by the Federal Communications Commission (FCC).

  1. Radio Observations of SN 2006fo

    NASA Astrophysics Data System (ADS)

    Soderberg, Alicia

    2006-09-01

    "I observed the Type Ibc SN 2006fo (IAUC 8750, CBET 643) with the Very Large Array on Sep 26.2 UT as part of an ongoing program to study the radio properties of SNe Ibc discovered through the SDSS SN survey. SN 2006fo is not detected at 8.5 or 22.5 GHz. At a distance of 88 Mpc, the radio luminosity of SN 2006fo is at least a factor of 100 lower than that of SN 1998bw at a similar epoch (Kulkarni et al., 1998, Nature, 395, 663).

  2. Radio Observations of SN 2006jc

    NASA Astrophysics Data System (ADS)

    Soderberg, Alicia

    2006-10-01

    "I observed the Type Ib SN 2006jc (CBET 666) with the Very Large Array on Oct 14.7 and Oct 15.7 UT as part of an ongoing program to study the radio properties of Type Ibc supernovae. SN 2006jc is not detected at 4.9, 8.5 or 22.5 GHz. At a distance of 24 Mpc, the radio luminosity of SN 2006jc is at least a factor of 100 lower than that of SN 1998bw at a similar epoch (Kulkarni et al., 1998, Nature, 395, 663).

  3. Bandwidth and repetition rate programmable Nyquist sinc-shaped pulse train source based on intensity modulators and four-wave mixing.

    PubMed

    Cordette, S; Vedadi, A; Shoaie, M A; Brès, C-S

    2014-12-01

    We propose and experimentally demonstrate an all-optical Nyquist sinc-shaped pulse train source based on intensity modulation and four-wave mixing. The proposed scheme allows for the tunability of the bandwidth and the full flexibility of the repetition rate in the limit of the electronic bandwidth of the modulators used through the flexible synthesis of rectangular frequency combs. Bandwidth up to 360 GHz at 40 GHz rate and up to 45 frequency lines at 5 GHz rate are demonstrated with 40 GHz modulators.

  4. Design optimization of the 34-meter DSN-NCP antennas

    NASA Technical Reports Server (NTRS)

    Levy, R.

    1984-01-01

    The new NASA Deep Space Network (DSN) 34-m-diameter azimuth-elevation (Az-El) antenna structure is an example of an essentially computer-automated design. In addition to pivotal comptuer Lagrange multiplier design optimization software, much of the associated pre- and post-processing was also performed by computer. The construction of one of these antennas at Goldstone, California, is well advanced and will be completed this summer. A second installation is in progress in Australia. Both atennas will be used primarily for spacecraft tracking and will operate in the 8.5-GHz, 3.5-cm (1.4-in.) wavelength microwave frequency.

  5. Fade-durations derived from land-mobile-satellite measurements in Australia

    NASA Astrophysics Data System (ADS)

    Hase, Yoshihiro; Vogel, Wolfhard J.; Goldhirsh, Julius

    1991-05-01

    Transmissions from the Japanese ETS-V geostationary satellite were measured at L band (1.5 GHz) in a vehicle driving on roads of southeastern Australia. The measurements were part of a program designed to characterize propagation effects due to roadside trees and terrain for mobile satellite service. It is shown that the cumulative distributions of fade and nonfade durations follow a lognormal and power law, respectively. At 1 percent probability, fades last 2-8 m, and nonfades 10-100 m, depending on the degree of shadowing. Phase fluctuations are generally small, allowing the channel characteristics to be estimated from levels only.

  6. New dual-reflector feed system for the Nancay radio telescope

    NASA Astrophysics Data System (ADS)

    Granet, Christophe; James, Graeme L.; Pezzani, Jacques

    1997-09-01

    A new compact dual-reflector Gregorian feed system has been designed to improve the overall performance of the Nancay radio telescope. To operate continuously within the 1.0-3.5-GHz band, two wideband compact corrugated horns are used. The new feed system improves the sensitivity of the telescope by a factor between 2 and 3. To verify the theoretical design, a 1/20th-scale model was constructed and tested. The measured results were in excellent agreement with the predicted values.

  7. Imaging in a Gregorian antenna from 12 to 30 GHz

    NASA Astrophysics Data System (ADS)

    Dragone, Corrado; Ruscio, J. T.

    1988-02-01

    A Gregorian antenna with the main reflector illuminated by a magnified image of a small horn aperture was built and tested from 12 to 30 GHz. The image is approximately frequency-independent, and the main reflector is illuminated with negligible spillover. Polarization distortion caused by aberration is very small, in excellent agreement with a simple expression derived previously by the author (1987). Spatial filtering by the subreflector causes the far-field sidelobes in the principal plane orthogonal to the symmetry plane to be very low, about 80 dB below the main beam at 16.5 GHz for angles from the axis that are greater than 20 deg.

  8. A systems-oriented single event effects test approach for high speed digital phase-locked loops

    SciTech Connect

    Jobe, K.; Shoga, M.; Koga, R.

    1996-12-01

    A systems-oriented single event effects (SEE) test approach is outlined here for two different phase-locked loop (PLL) application specific integrated circuits (ASICs) used for spaceborne local oscillator (LO) generation. The system considerations in designing the upset detection technique is described. This is the only known technique for getting information critical to the system about single event upset (SEU) sensitivity at speed for PLLs. Test results are presented for PLL devices operating at clock speeds of 1.0 and 1.5 GHz. Significant frequency effects were not observed in these devices since the clock speed varied only 50%.

  9. VizieR Online Data Catalog: ROSAT AGN content (Brinkmann+, 1995)

    NASA Astrophysics Data System (ADS)

    Brinkmann, W.; Siebert, J.; Reich, W.; Fuerst, E.; Reich, P.; Voges, W.; Truemper, J.; Wielebinski, R.

    1996-05-01

    The cross-correlation of the source list from the ROSAT All-Sky Survey with the 5 GHz Green Bank survey yields a list of 2127 objects. About two thirds of them are optically unidentified. The majority of the objects with known optical counterparts are quasars and radio galaxies, most of them detected in X-rays for the first time. In this paper we present a list of the previously optically identified objects with their main characteristics and discuss their general (bulk) properties. We find strong correlations between luminosities in the radio, optical, and X-ray bands which differ for quasars and radio galaxies. (1 data file).

  10. DETECTION AND FLUX DENSITY MEASUREMENTS OF THE MILLISECOND PULSAR J2145–0750 BELOW 100 MHz

    SciTech Connect

    Dowell, J.; Taylor, G. B.; Craig, J.; Henning, P. A.; Schinzel, F.; Ray, P. S.; Blythe, J. N.; Clarke, T.; Helmboldt, J. F.; Ellingson, S. W.; Wolfe, C. N.; Lazio, T. J. W.; Stovall, K.

    2013-09-20

    We present flux density measurements and pulse profiles for the millisecond pulsar PSR J2145–0750 spanning 37 to 81 MHz using data obtained from the first station of the Long Wavelength Array. These measurements represent the lowest frequency detection of pulsed emission from a millisecond pulsar to date. We find that the pulse profile is similar to that observed at 102 MHz. We also find that the flux density spectrum between ≈40 MHz to 5 GHz is suggestive of a break and may be better fit by a model that includes spectral curvature with a rollover around 730 MHz rather than a single power law.

  11. Free space propagation of concentric vortices through underwater turbid environments

    NASA Astrophysics Data System (ADS)

    Morgan, K. S.; Miller, J. K.; Cochenour, B. M.; Li, W.; Li, Y.; Watkins, R. J.; Johnson, E. G.

    2016-10-01

    Concentric optical vortex beams of 3-petal, 5-petal, and 6-petal spatial profiles are generated at 450 nm using a single diffractive optical element. The spatial and temporal propagation characteristics of these beams are then studied in a scattering underwater environment. Experimental results demonstrate a less than 5% reduction in the spatial pattern for turbidities in excess of 10 attenuation lengths. The temporal properties of concentric vortex beams are studied by temporally encoding an on-off keyed, non-return-to-zero (OOK-NRZ) data stream at 1.5 GHz.

  12. Generation of constant-amplitude radio-frequency sweeps at a tunnel junction for spin resonance STM.

    PubMed

    Paul, William; Baumann, Susanne; Lutz, Christopher P; Heinrich, Andreas J

    2016-07-01

    We describe the measurement and successful compensation of the radio-frequency transfer function of a scanning tunneling microscope over a wide frequency range (15.5-35.5 GHz) and with high dynamic range (>50 dB). The precise compensation of cabling resonances and attenuations is critical for the production of constant-voltage frequency sweeps for electric-field driven electron spin resonance (ESR) experiments. We also demonstrate that a well-calibrated tunnel junction voltage is necessary to avoid spurious ESR peaks that can arise due to a non-flat transfer function. PMID:27475577

  13. Electric Field Distribution Excited by Indoor Radio Source for Exposure Compliance Assessment

    NASA Astrophysics Data System (ADS)

    Higashiyama, Junji; Tarusawa, Yoshiaki

    Correction factors are presented for estimating the RF electromagnetic field strength in the compliance assessment of human exposure from an indoor RF radio source in the frequency range from 800MHz to 3.5GHz. The correction factors are derived from the increase in the spatial average electric field strength distribution, which is dependent on the building materials. The spatial average electric field strength is calculated using relative complex dielectric constants of building materials. The relative complex dielectric constant is obtained through measurement of the transmission and reflection losses for eleven kinds of building materials used in business office buildings and single family dwellings.

  14. Multi-channel nonlinearity compensation of PDM-QPSK signals in dispersion-managed transmission using dispersion-folded digital backward propagation.

    PubMed

    Xia, Cen; Liu, Xiang; Chandrasekhar, S; Fontaine, N K; Zhu, Likai; Li, G

    2014-03-10

    We demonstrate nonlinearity compensation of 37.5-GHz-spaced 128-Gb/s PDM-QPSK signals using dispersion-folded digital-backward-propagation and a spectrally-sliced receiver that simultaneously receives three WDM signals, showing mitigation of intra-channel and inter-channel nonlinear effects in a 2560-km dispersion-managed TWRS-fiber link. Intra-channel and adjacent inter-channel nonlinear compensation gains when WDM channels are fully populated in the C-band are estimated based on the GN-model. PMID:24663923

  15. Polymeric MST - high precision at low cost

    NASA Astrophysics Data System (ADS)

    Elderstig, Håkan; Larsson, Olle

    1997-09-01

    A low-cost production process for fabrication of polymeric microstructures from micromachined silicon is demonstrated in a splice for the splicing of optical fibers and an optical motherboard. Measurements on splices showed less than 0.5 dB insertion losses. The prototype polymeric motherboard concisted of an optical receiver module. The detector that was mounted on the polymeric optical motherboard detected about 70% of the transferred light. Measurements with modulated light indicates an optical bandwidth of 5 GHz at 2 V reverse current on the pin-diode.

  16. Spectrally-efficient all-optical OFDM by WSS and AWG.

    PubMed

    Hoxha, J; Morosi, J; Shimizu, S; Martelli, P; Boffi, P; Wada, N; Cincotti, G

    2015-05-01

    We report on the transmission experiment of seven 12.5-GHz spaced all optical-orthogonal frequency division multiplexed (AO-OFDM) subcarriers over a 35-km fiber link, using differential quadrature phase shift keying (DQPSK) modulation and direct detection. The system does not require chromatic dispersion compensation, optical time gating at the receiver (RX) or cyclic prefix (CP), achieving the maximum spectral efficiency. We use a wavelength selective switch (WSS) at the transmitter (TX) to allow subcarrier assignment flexibility and optimal filter shaping; an arrayed waveguide grating (AWG) AO-OFDM demultiplexer is used at the RX, to reduce the system cost and complexity. PMID:25969193

  17. Wavelength tunable coherent burst-mode receiver design under transient frequency offset.

    PubMed

    Xu, Bo; Qiu, Kun

    2013-08-26

    Wavelength tunable optical coherent burst-mode receivers (BMR) can offer flexibility and sub-wavelength granularity for dynamic WDM networks. A new BMR design with dispersion equalizer plus frequency offset estimator is proposed for simultaneous dispersion compensation and frequency offset estimation. Its good performance is verified by simulations. A training sequence as short as 4 K symbols, corresponding to an initialization time of 160 ns, is found to be enough to support 200 km transmission distance plus over ± 5 GHz frequency offset. The new BMR design can also work under the case when transient frequency offset from wavelength tuning exists in the system.

  18. Syndiotactic Polystyrene/Hybrid Silica Spheres of POSS Siloxane Composites Exhibiting Ultralow Dielectric Constant.

    PubMed

    Joseph, Angel Mary; Nagendra, Baku; Surendran, K P; Gowd, E Bhoje

    2015-09-01

    Homogeneously dispersed hybrid silica/syndiotactic polystyrene composites were investigated for low-κ dielectric applications. The composites were prepared by a solution blending method, and their microstructures were analyzed by SEM, TEM, and AFM. Crystallization and phase transformation behavior of sPS were investigated using differential scanning calorimetry and wide-angle X-ray diffraction. These composites exhibited improved thermal stability and reduced thermal expansion coefficients. Promising dielectric properties were observed for the composites in the microwave frequency region with a dielectric constant (κ = 1.95) and loss (tan δ = 10(-4)) at 5 GHz. PMID:26287385

  19. Superconducting microstrip resonator for pulsed ESR of thin films.

    PubMed

    Benningshof, O W B; Mohebbi, H R; Taminiau, I A J; Miao, G X; Cory, D G

    2013-05-01

    This article describes a superconducting microstrip resonator operating at 9.5 GHz (X-band) that is specially designed for pulsed ESR on thin films. A novel configuration consisting of an array of half-wave length microstrip transmission lines generates a uniform magnetic field over a 2-D region of 100×1000 μm(2) with field homogeneity better than 5×10(-2). Using the device, we demonstrate strong coupling of the resonator to an electron spin ensemble and pulsed ESR on Si:P.

  20. Current-induced resonant depinning of a transverse magnetic domain wall in a spin valve nanostrip

    NASA Astrophysics Data System (ADS)

    Metaxas, P. J.; Anane, A.; Cros, V.; Grollier, J.; Deranlot, C.; Lemaître, Y.; Xavier, S.; Ulysse, C.; Faini, G.; Petroff, F.; Fert, A.

    2010-11-01

    We study the impact of rf and dc currents on domain wall depinning in the soft layer of a 120 nm wide Co/Cu/NiFe spin valve nanostrip. A strong resonant reduction in the depinning field (from ˜75 to 25 Oe) is observed for rf currents near 3.5 GHz. Notably, the features of the resonant depinning depend not only on the rf current but also on the simultaneously applied dc current. Consequently, we discuss both the role of the adiabatic spin torque at resonance and that of the current generated Oersted fields.

  1. Frequency Reconfigurable Hybrid Slot Antenna Using PIN Diodes

    NASA Astrophysics Data System (ADS)

    Yang, Xiaolin; Sheng, Lili; Lin, Jiancheng; Chen, Gang

    2015-11-01

    This paper introduces a frequency reconfigurable hybrid slot antenna fed by coplanar waveguide (CPW) without complex bias network and DC blocking capacitor chips. In order to add reconfigurablility to the antenna, the PIN diodes are equipped in the slots. The antenna is capable of frequency switching at six different frequency bands between 1.7 GHz to 2.5 GHz, which can be used in multiradio wireless systems, such as DCS-1800, PCS1900, UMTS, Wibro and Bluetooth bands. The simulated and measured return loss, peak gain, together with the radiation patterns are presented and compared. Especially, the radiation patterns are stable at different frequency.

  2. Non-thermal plasma exhaust aftertreatment: Are all plasmas the same?

    SciTech Connect

    Whealton, J.H.; Hanson, G.R.; Storey, J.M.; Raridon, R.J.; Armfield, J.S.; Bigelow, T.S.; Graves, R.L.

    1997-12-31

    The authors describe initial experiments employing 5.5 GHz pulsed microwave power, which should result in enhanced chemistry compared to present state-of-the-art plasma aftertreatments by; reducing plasma electric field shielding, increasing availability of atomic nitrogen, exploiting surface charging of dielectrics, avoiding (low field) threshold initiated discharges, and achieving a higher high energy tail on the electron distribution function. As an example, the authors decided to test for NO reduction in N{sub 2}. While this reaction is not a complete description of the exhaust issues by any means, they thought it would demonstrate the technology proposed.

  3. Conceptual design and analysis of a large antenna utilizing electrostatic membrane management

    NASA Technical Reports Server (NTRS)

    Brooks, A. L.; Coyner, J. V.; Gardner, W. J.; Mihora, D. J.

    1982-01-01

    Conceptual designs and associated technologies for deployment 100 m class radiometer antennas were developed. An electrostatically suspended and controlled membrane mirror and the supporting structure are discussed. The integrated spacecraft including STS cargo bay stowage and development were analyzed. An antenna performance evaluation was performed as a measure of the quality of the membrane/spacecraft when used as a radiometer in the 1 GHz to 5 GHz region. Several related LSS structural dynamic models differing by their stiffness property (and therefore, lowest modal frequencies) are reported. Control system whose complexity varies inversely with increasing modal frequency regimes are also reported. Interactive computer-aided-design software is discussed.

  4. Polarization-insensitive unidirectional spoof surface plasmon polaritons coupling by gradient metasurface

    NASA Astrophysics Data System (ADS)

    Hong-yu, Shi; An-xue, Zhang; Jian-zhong, Chen; Jia-fu, Wang; Song, Xia; Zhuo, Xu

    2016-07-01

    A polarization-insensitive unidirectional spoof surface plasmon polariton (SPP) coupler mediated by a gradient metasurface is proposed. The field distributions and average Poynting vector of the coupled spoof SPPs are analyzed. The simulated and experimental results support the theoretical analysis and indicate that the designed gradient metasurface can couple both the parallel-polarized and normally-polarized incident waves to the spoof SPPs propagating in the same direction at about 5 GHz. Project supported by the China Postdoctoral Science Foundation (Grant No. 2015M580849) and the National Natural Science Foundation of China (Grant Nos. 61471292, 61501365, 61471388, 61331005, 41404095, and 41390454).

  5. Cryogenic, low-noise high electron mobility transistor amplifiers for the Deep Space Network

    NASA Technical Reports Server (NTRS)

    Bautista, J. J.

    1993-01-01

    The rapid advances recently achieved by cryogenically cooled high electron mobility transistor (HEMT) low-noise amplifiers (LNA's) in the 1- to 10-GHz range are making them extremely competitive with maser amplifiers. In order to address future spacecraft navigation, telemetry, radar, and radio science needs, the Deep Space Network is investing both maser and HEMT amplifiers for its Ka-band (32-GHz) downlink capability. This article describes the current state cryogenic HEMT LNA development at Ka-band for the DSN. Noise performance results at S-band (2.3 GHz) and X-band (8.5 GHz) for HEMT's and masers are included for completeness.

  6. e-EVN detections of GRB130427A and GRB130702A

    NASA Astrophysics Data System (ADS)

    Paragi, Z.; van der Horst, A. J.; Yang, J.; Kouveliotou, C.; Wijers, R. A. M. J.; Granot, J.

    2013-08-01

    We observed GRB130427A (GCN #14448, #14455, #14471, #14480, #14494) at 5 GHz with the European VLBI Network on 2013 May 3 from 15:50 UT till 02:20 UT the next day. All e-EVN stations in Europe, and the telescopes in Shanghai, Hartebeesthoek and Arecibo participated in the observations. The aggregate bitrate was 1024 Mbps for most telescopes. Shanghai and Arecibo observed the same bandwidth but at a lower bitrate of 512 Mbps and using 1-bit sampling.

  7. Preparation of a primary argon beam for the CERN fixed target physics

    NASA Astrophysics Data System (ADS)

    Küchler, D.; O'Neil, M.; Scrivens, R.; Thomae, R.

    2014-02-01

    The fixed target experiment NA61 in the North Area of the Super Proton Synchrotron is studying phase transitions in strongly interacting matter. Up to now they used the primary beams available from the CERN accelerator complex (protons and lead ions) or fragmented beams created from the primary lead ion beam. To explore a wider range of energies and densities a request was made to provide primary argon and xenon beams. This paper describes the results of the setting up and 10 week test run of the Ar11+ beam from the 14.5 GHz ECR ion source and the linear accelerator (Linac3) at CERN.

  8. Enhancement of the low-frequency response of a reflective semiconductor optical amplifier slow light-based microwave phase shifter by forced coherent population oscillations

    NASA Astrophysics Data System (ADS)

    Meehan, Aidan; Connelly, Michael J.

    2014-05-01

    The enhancement of the low frequency gain response of a microwave phase shifter based on slow light in a bulk reflective semiconductor optical amplifier (RSOA), by using forced coherent population oscillations (FCPO), is experimentally demonstrated. FCPO is achieved by simultaneously modulating the input optical power and bias current. The beat signal gain improvement ranges from 45 to 0 dB over a frequency range of 0.5 to 2.5 GHz, thereby improving the noise performance of the phase shifter. Tunable phase shifts of up to 40º are possible over this frequency range.

  9. VizieR Online Data Catalog: Panchromatic observations of PTF11qcj (Corsi+, 2014)

    NASA Astrophysics Data System (ADS)

    Corsi, A.; Ofek, E. O.; Gal-Yam, A.; Frail, D. A.; Kulkarni, S. R.; Fox, D. B.; Kasliwal, M. M.; Sullivan, M.; Horesh, A.; Carpenter, J.; Maguire, K.; Arcavi, I.; Cenko, S. B.; Cao, Y.; Mooley, K.; Pan, Y.-C.; Sesar, B.; Sternberg, A.; Xu, D.; Bersier, D.; James, P.; Bloom, J. S.; Nugent, P. E.

    2016-02-01

    On 2011 November 1, we discovered PTF11qcj in an R-band image from the 48 inch Samuel Oschin telescope at Palomar Observatory (P48), which is routinely used by the Palomar Transient Factory (PTF). Subsequent observations with the P48 were conducted with the Mould-R and Gunn-g filters. Photometry (Table2) was performed relative to the SDSS r-band and g-band magnitudes of stars in the field. Multi-color optical (gri) optical light curves were also obtained using the Palomar 60 inch telescope (P60) and the RATCAM optical imager on the robotic 2m Liverpool Telescope (LT) located at the Roque de Los Muchachos Observatory on La Palma. On 2011 November 15, we started a long-term monitoring campaign of PTF11qcj (along with calibrators J1327+4326 and 3C 286) with the Karl G. Jansky Very Large Array (VLA; http://public.nrao.edu/telescopes/vla) in its D, DnC, C, CnB, and A configurations, under our Target of Opportunity programs (VLA/11A-227, VLA/11B-034, VLA/11B-247, VLA/12B-195; PI: A. Corsi). The light curves of PTF11qcj at frequencies of 2.5GHz, 3.5GHz, 5GHz, 7.4GHz, 13.5GHz, 16GHz are reported in Table3. We also observed the field of PTF11qcj (together with the test calibrator J1203+480) using the Combined Array for Research in Millimeter-wave Astronomy (CARMA; http://www.mmarray.org/), at a frequency of 93GHz. The data collected on 2011 November 19 and 2011 November 26 (CARMA program no. c0857; PI: A. Horesh) both resulted in a detection of PTF11qcj (Table3). We have carried out an X-ray monitoring campaign of PTF11qcj with Chandra and Swift. All our Swift-XRT observations yielded non detections (see Table 4), while Chandra detected PTF11qcj in three epochs (DDT proposals nos. 501793, 501794, 501797; PI: A. Corsi). The results of our X-ray follow-up are reported in Table4. We observed the position of PTF11qcj with Spitzer on two epochs (on 2012 March 28.747 and 2012 June 25.643; Table5; DDT proposal no. 31731; PI: A. Corsi). On 2012 March 28 (Table5), we also observed

  10. Resonance-enhanced waveguide-coupled silicon-germanium detector

    NASA Astrophysics Data System (ADS)

    Alloatti, L.; Ram, R. J.

    2016-02-01

    A photodiode with 0.55 ± 0.1 A/W responsivity at a wavelength of 1176.9 nm has been fabricated in a 45 nm microelectronics silicon-on-insulator foundry process. The resonant waveguide photodetector exploits carrier generation in silicon-germanium within a microring which is compatible with high-performance electronics. A 3 dB bandwidth of 5 GHz at -4 V bias is obtained with a dark current of less than 20 pA.

  11. Propagation effects by roadside trees measured at UHF and L-band for mobile satellite systems

    NASA Technical Reports Server (NTRS)

    Goldhirsh, Julius; Vogel, Wolfhard J.

    1988-01-01

    Propagation field tests were performed in Central Maryland and involved a helicopter and mobile van as the source and receiving platforms, respectively. Tests were implemented at both UHF (870 MHz) and L-band (1.5 GHz) during a period in which the trees were in full blossom and contained maximum moisture. Cumulative fade distributions were determined from the data for various fixed elevation angles, side of the road driving, and road types for both worst and best case path geometries and for overall average road conditions.

  12. Cooperative proton transfer and tunneling in dye doped benzoic acid crystals

    NASA Astrophysics Data System (ADS)

    Rambaud, Ch.; Trommsdorff, H. P.

    1999-06-01

    In seleno-indigo doped benzoic acid crystals, the energy level structure of a pair of benzoic acid dimers coupled to the impurity center is characterized by optical spectroscopy and transient hole burning in electric fields. The lowest energy states involve degenerate, polar proton configurations. Proton tunneling lifts this degeneracy. The tunneling matrix element for proton transfer in a benzoic acid dimer equals 6.5±1.5 GHz, a value comparable to those found with other guest molecules. Relaxation between the two ground state levels involves the concerted motion of four protons and determines the intensity distribution of the fine structure observed in hole burning.

  13. A low-noise double-dipole antenna SIS mixer at 1 THz

    NASA Astrophysics Data System (ADS)

    Shitov, S. V.; Jackson, B. D.; Baryshev, A. M.; Markov, A. V.; Iosad, N. N.; Gao, J.-R.; Klapwijk, T. M.

    2002-08-01

    A quasi-optical mixer employing a Nb/Al/AlO x/Nb twin-SIS junction with a NbTiN/SiO 2/Al microstrip coupling circuit is tested at 800-1000 GHz. The receiver noise temperature TRX=250 K (DSB) is measured at 935 GHz for the bath temperature 2 K at IF=1.5 GHz; TRX remains below 350 K within the frequency range 850-1000 GHz. The integrated lens-antenna demonstrated good beam symmetry with sidelobes below -16 dB.

  14. Nanosecond pulse shaping at 780 nm with fiber-based electro-optical modulators and a double-pass tapered amplifier

    NASA Astrophysics Data System (ADS)

    Rogers, C. E.; Gould, P. L.

    2016-02-01

    We describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized.

  15. Results from the first single cell Nb3Sn cavity coatings at JLab

    SciTech Connect

    Eremeev, Grigory

    2015-09-01

    Nb3Sn is a promising superconducting material for SRF applications and has the potential to exceed the limitations of niobium. We have used the recently commissioned Nb3Sn coating system to investigate Nb3Sn coatings on several single cell cavities by applying the same coating procedure on several different single cells with different history and pre-coating surface preparation. We report on our findings with four 1.5 GHz CEBAF-shape single cell and one 1.3 GHz ILC-shape single cavities that were coated, inspected, and tested.

  16. Exploring the conformational landscape of menthol, menthone, and isomenthone: a microwave study

    PubMed Central

    Schmitz, David; Shubert, V. Alvin; Betz, Thomas; Schnell, Melanie

    2015-01-01

    The rotational spectra of the monoterpenoids menthol, menthone, and isomenthone are reported in the frequency range of 2–8.5 GHz, obtained with broadband Fourier-transform microwave spectroscopy. For menthol only one conformation was identified under the cold conditions of the molecular jet, whereas three conformations were observed for menthone and one for isomenthone. The conformational space of the different molecules was extensively studied using quantum chemical calculations, and the results were compared with molecular parameters obtained by the measurements. Finally, a computer program is presented, which automatically identifies different species in a dense broadband microwave spectrum using calculated ab initio rotational constants as initial input parameters. PMID:25815287

  17. Determination of Torsional Barriers of Itaconic Acid and N-Acetylethanolamine Using Chirped-Pulsed Ftmw Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bailey, Josiah R.; McMahon, Timothy J.; Bird, Ryan G.; Pratt, David

    2015-06-01

    The ground state rotational spectrum of itaconic acid (methylenesuccinic acid) and N-acetylethanolamine (AEA) have been collected and analyzed over the frequency range of 7-17.5 GHz. Both molecules displayed an unexpected tunneling splitting pattern caused by a V2 and V3 barriers, respectively. AEA's methyl rotor is directly connected to a carbonyl and is expected to have too high of a barrier to internal motion. Itaconic acid contains no methyl groups or any symmetry, yet a torsional splitting was observed. The origin of this motion as well their barrier heights and lowest energy conformations will be discussed.

  18. Nanosecond pulse shaping at 780 nm with fiber-based electro-optical modulators and a double-pass tapered amplifier.

    PubMed

    Rogers, C E; Gould, P L

    2016-02-01

    We describe a system for generating frequency-chirped and amplitude-shaped pulses on time scales from sub-nanosecond to ten nanoseconds. The system starts with cw diode-laser light at 780 nm and utilizes fiber-based electro-optical phase and intensity modulators, driven by an arbitrary waveform generator, to generate the shaped pulses. These pulses are subsequently amplified to several hundred mW with a tapered amplifier in a delayed double-pass configuration. Frequency chirps up to 5 GHz in 2 ns and pulse widths as short as 0.15 ns have been realized. PMID:26906832

  19. Nonlinear study on the terahertz free electron laser amplifier with elliptical waveguide

    SciTech Connect

    Wang Minghong; Liu Pukun; Xue Qianzhong; Dong Ruixin

    2008-12-15

    The use of an elliptical waveguide and a planar wiggler with parabolically tapered pole pieces as the terahertz free electron laser (FEL) amplifier model is proposed. A set of self-consistent differential equations for the FEL amplifier is derived by using nonlinear theory, and the characteristics of this amplifier are numerically analyzed. Our numerical simulations are conducted to the 1000 GHz amplifier with an electron beam energy of 1.74 MeV. The results indicate that the peak power of 180 kW and frequency bandwidth of 13.5 GHz can be obtained.

  20. Radio polarization characteristics of two RS CVn binaries

    NASA Technical Reports Server (NTRS)

    Mutel, R. L.; Lestrade, J.-F.; Doiron, D. J.

    1985-01-01

    The results of multifrequency epoch VLA observations of polarized radio emission from the nearby active RS CVn binaries UX Arietis and HR 1099 are reported. For both systems, there is an excellent correlation between handedness of circular polarization and frequency. Helicity reversal is almost always seen between 1.4 and 5.0 GHz, possibly due to optical depth effects. There may also be an anticorrelation between total intensity and fractional circular polarization, especially at 5 GHz. This is consistent with models in which intense flares are associated with compact selfabsorbed synchrotron sources, while the quiescent emission arises from larger gyrosynchrotron-emitting plasma.

  1. Reducing flicker noise up-conversion in a 65nm CMOS VCO in the 1.6 to 2.6 GHz band

    NASA Astrophysics Data System (ADS)

    Pepe, Federico; Bonfanti, Andrea; Levantino, Salvatore; Samori, Carlo; Lacaita, Andrea Leonardo

    2013-05-01

    The demand of voltage-controlled oscillators (VCOs) with a broad tuning range can lead to unacceptable degradation of the 1/f3 phase-noise component if traditional voltage-biased topologies are implemented. In this paper, a novel VCO architecture is proposed, where a segmented transconductor tailors the negative-gm depending on the operating range to ensure that flicker noise up-conversion remains minimal. The implemented oscillator covers both 4G and WiMAX 2.5-GHz operation modes and achieves a 10-dB reduction of the 1/f3 phase noise without impairing the 1/f2 phase-noise performance.

  2. Monolithically integrated planar front-end photoreceivers with 0.25-micron gate pseudomorphic In(0.60)Ga(0.40)As/In(0.52)Al(0.48)As/InP modulation-doped field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lai, R.; Bhattacharya, P. K.; Pavlidis, D.; Brock, T.

    1991-02-01

    Monolithically InP-based pin-MODFET front-end photoreceivers realized by MBE regrowth have been characterized. The FWHM of the temporal response to photoexcitation for the full circuit was 60 psec, which translates to a bandwidth of approximately 6.5 GHz. The measured electrical 3-dB frequency response of the circuit with an effective input load resistance of 33 ohms is 15.0 GHz. The performance of the pin-MODFET photoreceiver circuit is comparable to the best hybrid circuits with InP-based devices.

  3. e-VLBI observations of Cyg X-3

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Paragi, Z.; Fender, R.; Spencer, R.; Garrett, M.; Rushton, A.

    2008-04-01

    We observed the X-ray binary Cyg X-3 on April 9th, 2008 for 9.5 hours, between 03:30-13:00 UT, at 5 GHz with the European VLBI Network (EVN) in e-VLBI mode (the data from the radio telescopes are sent over optical fibers in real-time to the correlator for processing). The radio telescopes participating in the experiment were: Cambridge, Medicina, Jodrell Bank MkII, Onsala (25 m), Torun and Westerbork (phased array).

  4. Radio non-detection of Aql X-1

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Paragi, Z.; Altamirano, D.; Miller-Jones, J. C. A.; Garrett, M.; Fender, R.; Rushton, A.; Spencer, R.; Maitra, D.

    2010-10-01

    The neutron star X-ray binary Aql X-1 is on the decaying phase of a major outburst that peaked at optical and X-ray bands in mid-September (ATEL #2850, #2871, #2891, #2902). We observed the object at 5 GHz with the European VLBI Network (EVN) in the e-VLBI mode on 2010 October 4th between 18:20-22:09 UT. The participating stations were Cambridge, Effelsberg, Jodrell Bank (MkII), Hartebeesthoek, Medicina, Onsala, Torun, Westerbork and Yebes.

  5. e-VLBI observations of SS 433 in outburst

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Paragi, Z.; Trushkin, S.; Soleri, P.; Fender, R.; Garrett, M.; Spencer, R.; Rushton, A.; Burgess, P.; Kunert-Bajraszewska, M.; Pazderski, E.; Borkowski, K.; Hammargren, R.; Lindqvist, M.; Maccaferri, G.

    2008-11-01

    We have observed the X-ray binary SS 433 on November 6, 2008 between 13:48-18:35 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The radio telescopes participating in the experiment were: Medicina, Onsala 25m, Torun, Jodrell Bank MkII and Cambridge. The X-ray binary SS 433 is in outburst. Trushkin & Nizhelskij (ATel #1819) reported a major flare already active during the RATAN-600 observations in the 1-22 GHz band on 2008 October 28.

  6. Antenna evaluation study for the shuttle multispectral radar, phase 1

    NASA Technical Reports Server (NTRS)

    Coffey, E. L., III; Carver, K. R.

    1976-01-01

    Critical parameters of the shuttle multispectral radar antenna (SMRA) which most affect antenna performance were identified. A preliminary methematical model is presented for describing SMRA performance under the influence of various physical and environmental factors which might degrade performance. Because user groups have not agreed on optimum frequencies best suited for the broadest range of application, the study incorporates frequencies ranging from 1.2 to 14.5 GHz, as well as a consideration of incidence angles from near nadir to nearly 50 deg.

  7. Planar metamaterial based on hybridization for directive emission.

    PubMed

    Ourir, Abdelwaheb; Abdeddaim, Redha; de Rosny, Julien

    2012-07-30

    We present the first experimental demonstration of a high-directivity using a mu and epsilon near zero (MENZ) metamaterial. We use the hybridization principles to design a planar MENZ structure based on the fishnet unit cell. Resonant mode engineering achieves an effective permittivity and permeability that approaches zeros around 10.5 GHz simultaneously. We use this metamaterial as a superstrate of a microstrip patch antenna. We show that the directivity of the antenna is effectively enhanced compared to that of the patch antenna alone at the desired frequency. PMID:23038307

  8. Dielectric Properties of 4-methoxy-4'-cyanobiphenyl (1 OCB) in the Supercooled Isotropic and Nematic Phases

    NASA Astrophysics Data System (ADS)

    Urban, Stanisław; Gestblom, Bo; Pawlus, Sebastian

    2003-06-01

    Dielectric studies of 4-methoxy-4'-cyanobiphenyl (1 OCB) in the supercooled isotropic and nematic phases were performed with the aid of three set-ups covering the frequency range 10 kHz - 5 GHz. In the static measurements the nematic phase could be supercooled down to 25 K below the clearing point, whereas in the dynamic studies a 12 K range was covered in a single run. The relaxation times and activation enthalpies characterising the molecular rotations around the principal inertia moment axes were determined. The predictions of theories based on the assumption of the rod-like molecules are well applicable to the dielectric data obtained.

  9. On the microwave measurement of precipitation in tropics

    NASA Technical Reports Server (NTRS)

    Weng, Fuzhong; Vonder Haar, Thomas H.

    1992-01-01

    The difference between the brightness temperature structure over a typical tropical rain system and that of the midlatitude thunderstorms is examined. It is also determined how the brightness temperature and the rain rate relationship at the microwave frequencies deviates from that in the thunderstorms. It is shown, in particular, that the theoretical brightness temperature and rain rate relationship at 19.35 GHz provides good estimates of the surface rain rates for either convective or stratiform precipitation, but the relationship at 37 and 85.5 GHz may result in a significant overestimation of surface rain rate, especially for stratiform precipitation.

  10. Radio Non-Detection of ASASSN-16jt/SN 2016cvk

    NASA Astrophysics Data System (ADS)

    Ryder, S. D.; Kool, E. C.; Stockdale, C. J.; Kotak, R.; Romero-Canizales, C.; Anderson, G.

    2016-09-01

    The apparently SN 2009ip-like transient ASASSN-16jt coincident with the Type IIn-pec SN 2016cvk (ATel #9439, #9445; http://wis-tns.weizmann.ac.il/object/2016cvk) in the galaxy ESO 344-G021 has been observed with the Australia Telescope Compact Array (ATCA) at 5.5 and 9 GHz on 2016 Sep 4.6 UT. No radio emission was detected at the reported location, to a 3-sigma upper limit of 68 microJy/beam (5.5 GHz) and 75 microJy/beam (9.0 GHz).

  11. Reconfigurable liquid metal circuits by Laplace pressure shaping

    NASA Astrophysics Data System (ADS)

    Cumby, Brad L.; Hayes, Gerard J.; Dickey, Michael D.; Justice, Ryan S.; Tabor, Christopher E.; Heikenfeld, Jason C.

    2012-10-01

    We report reconfigurable circuits formed by liquid metal shaping with <10 pounds per square inch (psi) Laplace and vacuum pressures. Laplace pressure drives liquid metals into microreplicated trenches, and upon release of vacuum, the liquid metal dewets into droplets that are compacted to 10-100× less area than when in the channel. Experimental validation includes measurements of actuation speeds exceeding 30 cm/s, simple erasable resistive networks, and switchable 4.5 GHz antennas. Such capability may be of value for next generation of simple electronic switches, tunable antennas, adaptive reflectors, and switchable metamaterials.

  12. First operation of the charge-breeder electron-cyclotron-resonance ion source at the Texas A and M Cyclotron Institute

    SciTech Connect

    May, D. P.; Tabacaru, G.; Abegglen, F. P.; Cornelius, W. D.

    2010-02-15

    The 14.5 GHz electron-cyclotron-resonance ion source (ECRIS) designed and fabricated specifically for charge breeding has been installed at the Texas A and M University Cyclotron Institute for use in the institute's ongoing radioactive-ion-beam upgrade. The initial testing of the source has just begun with magnetic analysis of the ECRIS beam. The source has only been conditioning for a brief time at low microwave power, and it is continuing to improve. After the source has been conditioned and characterized, charge-breeding trials with stable beams from a singly ionizing source will begin.

  13. High-Tc superconductor coplanar waveguide filter

    NASA Technical Reports Server (NTRS)

    Chew, Wilbert; Bajuk, Louis J.; Cooley, Thomas W.; Foote, Marc C.; Hunt, Brian D.; Rascoe, Daniel L.; Riley, A. L.

    1991-01-01

    Coplanar waveguide (CPW) low-pass filters made of YBa2Cu3O(7-delta) (YBCO) on LaAlO3 substrates, with dimensions suited for integrated circuits, were fabricated and packaged. A complete filter gives a true idea of the advantages and difficulties in replacing thin-film metal with a high-temperature superconductor in a practical circuit. Measured insertion losses in liquid nitrogen were superior to the loss of a similar thin-film copper filter throughout the 0- to 9.5-GHz passband. These results demonstrate the performance of fully patterned YBCO in a practical CPW structure after sealing in a hermetic package.

  14. An interferometric scanning microwave microscope and calibration method for sub-fF microwave measurements.

    PubMed

    Dargent, T; Haddadi, K; Lasri, T; Clément, N; Ducatteau, D; Legrand, B; Tanbakuchi, H; Theron, D

    2013-12-01

    We report on an adjustable interferometric set-up for Scanning Microwave Microscopy. This interferometer is designed in order to combine simplicity, a relatively flexible choice of the frequency of interference used for measurements as well as the choice of impedances range where the interference occurs. A vectorial calibration method based on a modified 1-port error model is also proposed. Calibrated measurements of capacitors have been obtained around the test frequency of 3.5 GHz down to about 0.1 fF. Comparison with standard vector network analyzer measurements is shown to assess the performance of the proposed system.

  15. Multi-channel nonlinearity compensation of PDM-QPSK signals in dispersion-managed transmission using dispersion-folded digital backward propagation.

    PubMed

    Xia, Cen; Liu, Xiang; Chandrasekhar, S; Fontaine, N K; Zhu, Likai; Li, G

    2014-03-10

    We demonstrate nonlinearity compensation of 37.5-GHz-spaced 128-Gb/s PDM-QPSK signals using dispersion-folded digital-backward-propagation and a spectrally-sliced receiver that simultaneously receives three WDM signals, showing mitigation of intra-channel and inter-channel nonlinear effects in a 2560-km dispersion-managed TWRS-fiber link. Intra-channel and adjacent inter-channel nonlinear compensation gains when WDM channels are fully populated in the C-band are estimated based on the GN-model.

  16. VizieR Online Data Catalog: 1.3 and 2mm survey of IRC+10216 (He+, 2008)

    NASA Astrophysics Data System (ADS)

    He, J. H.; Dinh-v-Trung, J. H.; Kwok, S.; Muller, H. S. P.; Zhang, Y.; Hasegawa, T.; Peng, T. C.; Huang, Y. C.

    2009-09-01

    The surveys were carried out using the 2mm receiver of the Arizona Radio Observatory (ARO) 12m Telescope (KP12M) at Kitt Peak (2005 April 26 to 2006 April 29) and the 1.3mm JT receiver of the Heinrich Hertz Submillimeter Telescope (SMT) at Mt. Graham (2005 October 31 to 2007 January 24). Observed frequency ranges are 131.2-160.3GHz for the 2mm survey, 219.5-245.5 and 251.5-267.5GHz for the 1.3mm survey. (1 data file).

  17. Characterization of onset of parametric decay instability of lower hybrid waves

    NASA Astrophysics Data System (ADS)

    Baek, S. G.; Bonoli, P. T.; Parker, R. R.; Shiraiwa, S.; Wallace, G. M.; Porkolab, M.; Takase, Y.; Brunner, D.; Faust, I. C.; Hubbard, A. E.; LaBombard, B. L.; Lau, C.

    2014-02-01

    The goal of the lower hybrid current drive (LHCD) program on Alcator C-Mod is to develop and optimize ITER-relevant steady-state plasmas by controlling the current density profile. Using a 4×16 waveguide array, over 1 MW of LH power at 4.6 GHz has been successfully coupled to the plasmas. However, current drive efficiency precipitously drops as the line averaged density (n¯e) increases above 1020m-3. Previous numerical work shows that the observed loss of current drive efficiency in high density plasmas stems from the interactions of LH waves with edge/scrape-off layer (SOL) plasmas [Wallace et al., Physics of Plasmas 19, 062505 (2012)]. Recent observations of parametric decay instability (PDI) suggest that non-linear effects should be also taken into account to fully characterize the parasitic loss mechanisms [Baek et al., Plasma Phys. Control Fusion 55, 052001 (2013)]. In particular, magnetic configuration dependent ion cyclotron PDIs are observed using the probes near n¯e≈1.2×1020m-3. In upper single null plasmas, ion cyclotron PDI is excited near the low field side separatrix with no apparent indications of pump depletion. The observed ion cyclotron PDI becomes weaker in inner wall limited plasmas, which exhibit enhanced current drive effects. In lower single null plasmas, the dominant ion cyclotron PDI is excited near the high field side (HFS) separatrix. In this case, the onset of PDI is correlated with the decrease in pump power, indicating that pump wave power propagates to the HFS and is absorbed locally near the HFS separatrix. Comparing the observed spectra with the homogeneous growth rate calculation indicates that the observed ion cyclotron instability is excited near the plasma periphery. The incident pump power density is high enough to overcome the collisional homogeneous threshold. For C-Mod plasma parameters, the growth rate of ion sound quasi-modes is found to be typically smaller by an order of magnitude than that of ion cyclotron quasi

  18. Development on JET of advanced tokamak operations for ITER

    NASA Astrophysics Data System (ADS)

    Tuccillo, A. A.; Crisanti, F.; Litaudon, X.; Baranov, Yu. F.; Becoulet, A.; Becoulet, M.; Bertalot, L.; Castaldo, C.; Challis, C. D.; Cesario, R.; DeBaar, M. R.; de Vries, P. C.; Esposito, B.; Frigione, D.; Garzotti, L.; Giovannozzi, E.; Giroud, C.; Gorini, G.; Gormezano, C.; Hawkes, N. C.; Hobirk, J.; Imbeaux, F.; Joffrin, E.; Lomas, P. J.; Mailloux, J.; Mantica, P.; Mantsinen, M. J.; Mazon, D.; Moreau, D.; Murari, A.; Pericoli-Ridolfini, V.; Rimini, F.; Sips, A. C. C.; Sozzi, C.; Tudisco, O.; Van Eester, D.; Zastrow, K.-D.; work-programme contributors, JET-EFDA

    2006-02-01

    Recent research on advanced tokamak in JET has focused on scenarios with both monotonic and reversed shear q-profiles having plasma parameters as relevant as possible for extrapolation to ITER. Wide internal transport barriers (ITBs), r/a ~ 0.7, are formed at ITER relevant triangularity δ ~ 0.45 and moderate plasma current, IP = 1.5-2.5 MA, with ne/nG ~ 60% when ELMs are moderated by Ne injection. At higher current (IP <= 3.5 MA, δ ~ 0.25) wide ITBs sitting at r/a >= 0.5, in the positive shear region, have been developed. Generally MHD events terminate these barriers otherwise limited in strength by power availability. ITBs with core density close to Greenwald value, Te ~ Ti and low toroidal rotation (4 times lower than standard ITBs) are obtained in plasma target preformed by opportune timing of lower hybrid current drive (LHCD), pellet injection and a small amount of NBI power. Wide ITBs, r/a ~ 0.6, of moderate strength, can be sustained without impurities accumulation for a time close to neoclassical resistive time in 3 T/1.8 MA discharges that exhibit reversed magnetic shear profiles and type-III ELMy edge. These discharges have been extended to the maximum duration allowed by JET subsystems (20 s) bringing to the record of injected energy in a JET discharge: E ~ 330 MJ. Portability of ITB physics has been addressed through dedicated similarity experiments. The ITB is identified as a layer of reduced diffusivity studying the propagation of the heat wave generated by modulating the ICRF mode conversion (MC) electron heating. Impressive results, QDT ~ 0.25, are obtained in these deuterium discharges with 3He minority when the MC layer is located in the core. The ion behaviour has been investigated in pure LHCD electron ITBs optimizing the 3He minority concentration for direct ion heating. Preliminary results of particle transport, studied via injection of a trace of tritium and an Ar-Ne mixture, will be presented.

  19. A thermodynamical analysis of rf current drive with fast electrons

    NASA Astrophysics Data System (ADS)

    Bizarro, João P. S.

    2015-08-01

    The problem of rf current drive (CD) by pushing fast electrons with high-parallel-phase-velocity waves, such as lower-hybrid (LH) or electron-cyclotron (EC) waves, is revisited using the first and second laws, the former to retrieve the well-known one-dimensional (1D) steady-state CD efficiency, and the latter to calculate a lower bound for the rate of entropy production when approaching steady state. The laws of thermodynamics are written in a form that explicitly takes care of frictional dissipation and are thus applied to a population of fast electrons evolving under the influence of a dc electric field, rf waves, and collisions while in contact with a thermal, Maxwellian reservoir with a well-defined temperature. Besides the laws of macroscopic thermodynamics, there is recourse to basic elements of kinetic theory only, being assumed a residual dc electric field and a strong rf drive, capable of sustaining in the resonant region, where waves interact with electrons, a raised fast-electron tail distribution, which becomes an essentially flat plateau in the case of the 1D theory for LHCD. Within the 1D model, particularly suited for LHCD as it solely retains fast-electron dynamics in velocity space parallel to the ambient magnetic field, an H theorem for rf CD is also derived, which is written in different forms, and additional physics is recovered, such as the synergy between the dc and rf power sources, including the rf-induced hot conductivity, as well as the equation for electron-bulk heating. As much as possible 1D results are extended to 2D, to account for ECCD by also considering fast-electron velocity-space dynamics in the direction perpendicular to the magnetic field, which leads to a detailed discussion on how the definition of an rf-induced conductivity may depend on whether one works at constant rf current or power. Moreover, working out the collisional dissipated power and entropy-production rate written in terms of the fast-electron distribution, it

  20. A thermodynamical analysis of rf current drive with fast electrons

    SciTech Connect

    Bizarro, João P. S.

    2015-08-15

    The problem of rf current drive (CD) by pushing fast electrons with high-parallel-phase-velocity waves, such as lower-hybrid (LH) or electron-cyclotron (EC) waves, is revisited using the first and second laws, the former to retrieve the well-known one-dimensional (1D) steady-state CD efficiency, and the latter to calculate a lower bound for the rate of entropy production when approaching steady state. The laws of thermodynamics are written in a form that explicitly takes care of frictional dissipation and are thus applied to a population of fast electrons evolving under the influence of a dc electric field, rf waves, and collisions while in contact with a thermal, Maxwellian reservoir with a well-defined temperature. Besides the laws of macroscopic thermodynamics, there is recourse to basic elements of kinetic theory only, being assumed a residual dc electric field and a strong rf drive, capable of sustaining in the resonant region, where waves interact with electrons, a raised fast-electron tail distribution, which becomes an essentially flat plateau in the case of the 1D theory for LHCD. Within the 1D model, particularly suited for LHCD as it solely retains fast-electron dynamics in velocity space parallel to the ambient magnetic field, an H theorem for rf CD is also derived, which is written in different forms, and additional physics is recovered, such as the synergy between the dc and rf power sources, including the rf-induced hot conductivity, as well as the equation for electron-bulk heating. As much as possible 1D results are extended to 2D, to account for ECCD by also considering fast-electron velocity-space dynamics in the direction perpendicular to the magnetic field, which leads to a detailed discussion on how the definition of an rf-induced conductivity may depend on whether one works at constant rf current or power. Moreover, working out the collisional dissipated power and entropy-production rate written in terms of the fast-electron distribution, it