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Sample records for kstar 5ghz lhcd

  1. Design and RF measurements of a 5 GHz 500 kW window for the ITER LHCD system

    NASA Astrophysics Data System (ADS)

    Hillairet, J.; Achard, J.; Bae, Y. S.; Bernard, J. M.; Dechambre, N.; Delpech, L.; Ekedahl, A.; Faure, N.; Goniche, M.; Kim, J.; Larroque, S.; Magne, R.; Marfisi, L.; Namkung, W.; Park, H.; Park, S.; Poli, S.; Vulliez, K.

    2014-02-01

    CEA/IRFM is conducting R&D efforts in order to validate the critical RF components of the 5 GHz ITER LHCD system, which is expected to transmit 20 MW of RF power to the plasma. Two 5 GHz 500 kW BeO pill-box type window prototypes have been manufactured in 2012 by the PMB Company, in close collaboration with CEA/IRFM. Both windows have been validated at low power, showing good agreement between measured and modeling, with a return loss better than 32 dB and an insertion loss below 0.05 dB. This paper reports on the window RF design and the low power measurements. The high power tests up to 500kW have been carried out in March 2013 in collaboration with NFRI. Results of these tests are also reported.

  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. Equilibrium of KSTAR Plasma

    NASA Astrophysics Data System (ADS)

    You, K.-I.; Lee, D.-K.; Lee, S. G.; Bak, J. G.; Hahn, S. H.; Lao, L.; Kstar Team

    2011-10-01

    We have installed the EFIT code on our computing system and made some modification to reconstruct the plasma equilibrium of KSTAR (Korea Superconducting Tokamak Advanced Research). KSTAR PF and TF coil systems use a CICC (Cable-In-Conduit Conductor) type superconductor. The CICC jacket material for most PF and all TF coils is Incoloy 908, which is a magnetic material with relative magnetic permeability greater than 10 in low external field. We newly introduced Diamagnetic Loop and variational Motion Stark Effect signals to equilibrium reconstruction. In this paper, we present some results of equilibrium reconstruction with the EFIT code, assess the effects of newly introduced diagnsotics signal on the equilibrium reconstruction and compare the EFIT results with the various diagnostics data in various plasma conditions including H- and L- modes. In addition, we will show the Incoloy908 effects on the plasma equilibrium.

  4. Progress in LHCD: a tool for advanced regimes on ITER

    NASA Astrophysics Data System (ADS)

    Tuccillo, A. A.; Barbato, E.; Bae, Y. S.; Becoulet, A.; Bernabei, S.; Bibet, P.; Calabrò, G.; Cardinali, A.; Castaldo, C.; Cesario, R.; Cho, M. H.; Cirant, S.; Crisanti, F.; Ekedahl, A.; Eriksson, L.-G.; Farina, D.; Giruzzi, G.; Goniche, M.; Granucci, G.; Ide, S.; Imbeaux, F.; Karttunen, S.; Litaudon, X.; Mailloux, J.; Mazon, D.; Mirizzi, F.; Moreau, D.; Nowak, S.; Namkung, W.; Panaccione, L.; Pericoli-Ridolfini, V.; Peysson, Y.; Petrzilka, V.; Podda, S.; Rantamaki, K.; Santini, F.; Saveliev, A.; Schneider, M.; Sozzi, C.; Suzuki, T.

    2005-12-01

    The recent success in coupling lower hybrid (LH) waves in high performance plasmas at JET together with the first demonstration on FTU of the coupling capability of the new passive active multijunction launcher removed major concerns on the possibility of using LH on ITER. LH exhibits the highest experimental current drive (CD) efficiency at low plasma temperature thus making it the natural candidate for off-axis CD on ITER where current profile control will help in maintaining burning performance on a long-time scale. We review recent LH results: long internal transport barrier obtained in JET with current profile sustained and controlled by LH acting under real time feedback together with first LH control of flat q-profile in a hybrid regime with Te ~ Ti. Minutes long fully non-inductive LH driven discharges on Tore Supra (TS). High CD efficiency with electron cyclotron in synergy with LH obtained in FTU and TS opening the possibility of interesting scenarii on ITER for MHD stabilization. Preliminary results of LH modelling for ITER are also reported. A brief overview of ITER LH system is reported together with some indication of new coming LH experiments, in particular KSTAR where CW klystrons at the foreseen ITER frequency of 5 GHz are being developed.

  5. 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.

  6. Thin CVD-diamond RF Pill-Box vacuum windows for LHCD systems

    NASA Astrophysics Data System (ADS)

    Ravera, G. L.; Ceccuzzi, S.; Cardinali, A.; Cesario, R.; Mirizzi, F.; Schettini, G.; Tuccillo, A. A.

    2014-02-01

    The preliminary assessment of a Lower Hybrid Current Drive (LHCD) system for the DEMOnstration power plant (DEMO) is mainly focused on the R&D needs of the less conventional RF components of the Main Transmission Line (MTL) and of the launcher. 500 kW, CW klystrons will be used to deliver the RF power to independent Passive Active Multijunction (PAM) launcher modules at 5 GHz. This paper describes the criteria followed to investigate the optimum solution for the RF window used as vacuum barrier between the MTL and the launcher, an open issue in the LHCD system for ITER too. The best candidate, capable of withstanding a power level of, or above, 0.5 MW in CW operation and to satisfy the electrical and thermonuclear requirements, is a Pill-Box assembly, based on a thin single disk of CVD-diamond as dielectric, water cooled at the edge. A thickness of 3 mm, much shorter than half a wavelength of the TE°11 mode in the dielectric as in the conventional window (unfeasible and too expensive with CVD-diamond at these frequencies), is sufficient to limit the exerted stress at the edge under the fracture stress for a maximum pressure applied of 0.9 MPa. In this paper the simulation results of conventional and thin CVD-diamond vacuum windows are presented comparing S-parameters, losses and electric fields in both matching condition and with VSWR = 2, using WR284 and WR229 as input/output rectangular waveguide.

  7. Second Harmonic Breakdown in KSTAR

    SciTech Connect

    Bae, Y. S.; England, A. C.; Kwon, M.; Lee, G. S.

    2007-09-28

    An 84-GHz electron cyclotron heating (ECH) system is being installed on the KSTAR tokamak. KSTAR adopts ECH-assisted start-up for the flexibility and reliability of the KSTAR operation with the plasma breakdown voltage reduced. The available maximum power of the 84 GHz ECH system is presently 500 kW with maximum duration of 2 s. Currently, the second harmonic ECH-assisted start-up is under consideration because a low toroidal field of B{sub T}{approx}1.5 T is desirable for safety and also for the high-beta experiments in the initial operation phase. The studies in this paper are on the effectiveness of the second harmonic breakdown using a 0-D time dependent plasma evolution code and the comparison with the recent DIII-D experimental results on the second harmonic pre-ionization.

  8. Infrared heterodyne receivers with IF responses approaching 5 GHz

    NASA Technical Reports Server (NTRS)

    Wolczok, J. M.; Peyton, B. J.

    1980-01-01

    Specialized coherent 10.6 micrometer infrared receivers were developed with infrared frequency responses approaching 5 GHz. Carbon dioxide lasers were employed for these applications because of their availability, stability, and high average power levels. Heterodyne receivers which employ extrinsic photoconductive Ge:Cu(Sb) mixers were developed for measurements of carbon dioxide laser scattering to determine: (1) the drive lower hybrid wave density fluctuations; and (2) the plasma ion temperature of the dense Tokamak plasmas.

  9. 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.

  10. The VLBA Imaging And Polarimetry Survey at 5 GHz

    SciTech Connect

    Helmboldt, J.F.; Taylor, G.B.; Tremblay, S.; Fassnacht, C.D.; Walker, R.C.; Myers, S.T.; Sjouwerman, L.O.; Pearson, T.J.; Readhead, A.C.S.; Weintraub, L.; Gehrels, N.; Romani, R.W.; Healey, S.; Michelson, P.F.; Blandford, R.D.; Cotter, G.; /New Mexico U. /UC, Davis /NRAO, Socorro /Caltech /NASA, Goddard /Stanford U., Phys. Dept. /KIPAC, Menlo Park /Oxford U.

    2006-11-20

    We present the first results of the VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey of 1,127 sources with flat radio spectra. Through automated data reduction and imaging routines, we have produced publicly available I, Q, and U images and have detected polarized flux density from 37% of the sources. We have also developed an algorithm to use each source's I image to automatically classify it as a point-like source, a core-jet, a compact symmetric object (CSO) candidate, or a complex source. Using data from the Sloan Digital Sky Survey (SDSS), we have found no significant trend between optical flux and 5 GHz flux density for any of the source categories. Using the velocity width of the H{beta} emission line and the monochromatic luminosity at 5100 to estimate the central black hole mass, M{sub BH}, we have found a weak trend between M{sub BH} and 5 GHz luminosity density for objects with SDSS spectra. Ongoing optical follow-up for all VIPS sources will allow for more detailed explorations of these issues. The mean ratio of the polarized to total 5 GHz flux density for VIPS sources with detected polarized flux density ranges from 1% to 20% with a median value of about 5%. This ratio is a factor of {approx}3 larger if only the jet components of core-jet systems are considered and is noticeably higher for relatively large core-jet systems than for other source types, regardless of which components (i.e., core, jet, or both) are considered. We have also found significant evidence that the directions of the jets in core-jet systems tend to be perpendicular to the electric vector position angles (EVPAs). The data is consistent with a scenario in which {approx}24% of the polarized core-jets have EVPAs that are anti-aligned with the directions of their jet components and which have a substantial amount of Faraday rotation. Follow-up observations at multiple frequencies will address this issue in more detail. In addition to these initial results, plans for

  11. The MIT-Green Bank (MG) 5 GHz survey

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    The catalog yielded by the MIT-Green Bank 5-GHz survey contains 5974 sources with S/N ratio greater than 5; a supplemental catalog contains 3836 possible detections with S/N of less than 5. The reliability of the main list is measured to be about 96 percent, with a completeness of about 95 percent. Flux density errors are a function of flux density. A comparison is presently made of survey sources from the Douglas et al. (1980) 365-MHz Texas survey; spectral indices are computed for coincident sources, and the distribution of spectral indices is discussed.

  12. 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.

  13. Modeling of neutral beam injection heating and current drive during the ramp-up phase in KSTAR

    NASA Astrophysics Data System (ADS)

    Terzolo, L.

    2014-06-01

    For flexible control of the plasma pressure and the current profiles, which are essential for a high performance plasma with long pulse operation, KSTAR is going to implement several heating and current systems, which include Neutral Beam Injection (NBI), Ion Cyclotron Resonant Heting (ICRH)/Fast Wave Current Drive (FWCD), Lower Hybrid Current Drive (LHCD), and Eclectron Cyclotron Heating (ECH)/Electron Cyclotron Current Drive (ECCD). Here, the NBI system is typically used for the central heating and current drive. For the time being, only one NBI device (composed of 3 sources) is available in KSTAR. The first two sources were successfully commissioned in 2010 and 2013. The last source will be installed in 2014. In this work, we present a simulation study of the heating and current drive of the first NBI system (3 sources) during the ramp-up phase. We consider two different NBI configurations (low and high beam energy). The simulation is performed with NUBEAM, a well-recognized Monte-Carlo code. Several different types of KSTAR target equilibria (scan from lower to higher plasma density) are used for the calculation of the current drive, the heating and the different NB losses (shinethrough, charge exchange and bad orbit). The study shows the dependency of those quantities on the plasma density, the position of the NB source and the beam energy. It also shows that because of the shinethrough loss is too high, each NB source cannot be used when the plasma density is under a certain threshold. This study can be used to determine the starting time of the different NB sources during the KSTAR ramp-up phase.

  14. The second MIT-Green Bank 5 GHz survey

    SciTech Connect

    Langston, G.I.; Heflin, M.B.; Conner, S.R.; Lehar, J.; Carrilli, C.L. E. O. Hulburt Center for Space Research, Washington, DC )

    1990-03-01

    The MHT-Green Bank II (MG II) 5-GHz survey covers 1.51 sr of sky in the right ascension range 4-21 h between +17 and +39.15 deg declination (J2000.0). The final MG II catalog contains 6182 sources detected with a signal-to-noise ratio greater than 5. The MG II flux density limit is 41 mJy. The catalog was produced from two separate north and south surveys with the NRAO 91-m transit telescope. Spectral indices are computed for sources identified in the NRAO 1400-MHz Survey (Condon and Broderick, 1985). A comparison of the spectral-index distributions for sources above and below 10 deg Galactic latitude is presented. 18 refs.

  15. 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.

  16. Controlling Plasma Shapes in KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, B. J.; Lao, L. L.

    1997-11-01

    The proposed shape control system on KSTAR uses 14 external PF coils to control the position of a small number of critical points in the magnetic field geometry. Shape control is accomplished on the slow time scale (>= 100 ms) by the detection of the plasma boundary from the external magnetic measurements and then applying the shape control matrices to determine the correction currents. We present the work on the determination of the location and the number of magnetic probes and flux loops for the KSTAR design using the EFIT code, which uses realistic distributed current source constrained by equilibrium. First of all, EFIT is run in equilibrium mode to simulate the flux loop and the magnetic probe signals at a large number of likely locations around the surrounding vacuum vessel. The number and the location of these probes are then optimized by comparing the reconstructed results using the EFIT code utilizing these simulated signals to the original equilibrium. Finally, we perturb the simulated signals by 3-5% randomly and run the reconstruction for many cases to determine the accuracy of the reconstruction for this particular set of probes and loops.

  17. Simulation study of disruption characteristics in KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, Jongkyu; Kim, J. Y.; Kessel, C. E.; Poli, F.

    2012-10-01

    A detailed simulation study of disruption in KSTAR had been performed using the Tokamak Simulation Code(TSC) [1] during the initial design phase of KSTAR [2]. Recently, however, a partial modification in the structure of passive plate was made in relation to reduce eddy current and increase the efficiency of control of vertical position. A substantial change can then occur in disruption characteristics and plasma behavior during disruption due to changes in passive plate structure. Because of this, growth rate of vertical instability is expected to be increased and eddy current and its associated electomagnetic force are expected to be reduced. To check this in more detail, a new simulation study is here given with modified passive plate structure of KSTAR. In particular, modeling of vertical disruption that is vertical displacement event (VDE) was carried out. We calculated vertical growth rate for a drift phase of plasma and electromagnetic force acting on PFC structures and compared the results between in a new model and an old model. [4pt] [1] S.C. Jardin, N. Pomphrey and J. Delucia, J. Comp. Phys. 66, 481 (1986).[0pt] [2] J.Y. Kim, S.Y. Cho and KSTAR Team, Disruption load analysis on KSTAR PFC structures, J. Accel. Plasma Res. 5, 149 (2000).

  18. 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

    ... it first made spectrum available in the 5 GHz band for U-NII in 1997. The Commission believes that... spectrum, combined with the ease of deployment and operational flexibility provided by its U-NII rules... made available spectrum in the 5 GHz band for U-NII in 1997, it has gained much experience with...

  19. 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.

  20. 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.

  1. KSTAR Equilibrium Reconstruction with EFIT Code

    NASA Astrophysics Data System (ADS)

    You, Kwang-Il; Lee, D. K.; Hahn, S. H.; Lao, L. L.

    2007-11-01

    For application to the KSTAR (Korea Superconducting Tokamak Advanced Research) device, we have made some modification to the EFIT code and installed it on our computing system. The main function of EFIT is reconstruction of plasma equilibrium using discharge data. After every discharge, the code will be automatically run for a chosen time array and the results will be stored in the same way as experimental data will be. An MDSplus system will be used as the data storage for KSTAR; therefore, the EFIT reads experimental data from the MDSplus server and writes the results to it. We have added some subroutines to EFIT for direct link with the MDSplus server and also converted EFIT to Fortran 95 form. Test runs of the code will be made by using plasma simulator in the KSTAR plasma control system. This paper will also present some results of equilibrium data obtained with the equilibrium mode of EFIT.

  2. Equilibrium Reconstruction of KSTAR First Plasma

    NASA Astrophysics Data System (ADS)

    You, K.-I.; Lee, D. K.; Park, B. H.; Lee, S. G.; Bak, J. G.; Seo, S. H.; Hahn, S. H.; Lao, L. L.

    2008-11-01

    To reconstruct the plasma equilibrium of KSTAR (Korea Superconducting Tokamak Advanced Research), we have made some modification to the EFIT code and installed it on our computing system. An MDSplus system is used for the data storage of KSTAR; thus, the EFIT reads experimental data from the MDSplus server and writes the results to it. We have modified some subroutines of the EFIT code for direct link with the MDSplus server. KSTAR PF and TF coil systems use a CICC (Cable-In-Conduit Conductor) type superconductor. The CICC jacket material for most PF and all TF coils is Incoloy 908, which is a magnetic material with relative magnetic permeability greater than 10 in low external field. The Incoloy 908 effects should, therefore, be considered in analyzing the magnetic diagnostics data. In this paper, we present our efforts to reconstruct the plasma equilibrium with EFIT code, including the compensation of Incoloy 908 effects.

  3. Equilibrium reconstruction using EFIT code for KSTAR

    NASA Astrophysics Data System (ADS)

    You, Kwang-Il; Lee, D. K.; Jeon, Y. M.; Hahn, S. H.; Lao, L. L.

    2006-10-01

    For application to the KSTAR (Korea Superconducting Tokamak Advanced Research) device, we have made some modification to the EFIT code and installed it on our computing system. The main function of EFIT is reconstruction of plasma equilibrium using discharge data. After every discharge, the code will be run for a chosen time array and the results will be stored in the same way as experimental data will be. An MDSplus system will be used as the data storage for KSTAR; therefore, the EFIT reads experimental data from the MDSplus server and writes the results to it. We have added some subroutines to EFIT for direct link with the MDSplus server and also converted it to Fortran 95 form. Test runs of the code will be made by using the KSTAR plasma control system. This paper will also present results of equilibrium data obtained with the equilibrium mode of EFIT.

  4. 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.

  5. C-Mod MHD stability analysis with LHCD

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Fatima; Bhattacharjee, A.; Delgado, L.; Scott, S.; Wilson, J. R.; Wallace, G. M.; Shiraiwa, S.; Mumgaard, R. T.

    2016-10-01

    In lower hybrid current drive (LHCD) experiments on the Alcator C-Mod, sawtooth activity could be suppressed as the safety factor q on axis is raised above unity. However, in some of these experiments, after applying LHCD, the onset of MHD mode activity caused the current drive efficiency to significantly drop. Here, we study the stability of these experiments by performing MHD simulations using the NIMROD code starting with experimental EFIT equilibria. First, consistent with the LHCD experiment with no signature of MHD activity, MHD mode activity was also absent in the simulations. Second, for experiments with MHD mode activity, we find that a core n=1 reconnecting mode with dominate poloidal modes of m=2,3 is unstable. This mode is a resistive current-driven mode as its growth rate scales with a negative power of the Lundquist number in the simulations. In addition, with further enhanced reversed-shear q profile in the simulations, a core double tearing mode is found to be unstable. This work is supported by U.S. DOE cooperative agreement DE-FC02-99ER54512 using the Alcator C-Mod tokamak, a DOE Office of Science user facility.

  6. 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.

  7. The Status of KSTAR and Research Plan

    NASA Astrophysics Data System (ADS)

    Park, H. K.; Oh, Y. K.; Yoon, S. W.; Kstar Team

    2016-10-01

    The Korean Superconducting Tokamak Advanced Research (KSTAR) capable of steady state operation of high beta plasmas, has achieved a significant progress in operation such as the longest ( 55 s) H-mode operation as well as newly discovered MHD and transport physics issues such as the interaction between ELMs and turbulence under RMP. The KSTAR is equipped with unique features for potentially unexplored tokamak physics and advanced control; 1) Lowest error field and magnetic ripple ideal for study of the influence of the tokamak plasma symmetry on stability and confinement study 2) Versatile magnetic perturbation tool with n = 1 , 2 IVCC coils for harmful MHD control including the ELMs and rotation control through NTV 3) Advanced 2D/3D imaging diagnostics for undisputed measurements for theory and modeling. In this talk, advances in research and vision toward the high beta long pulse operation in KSTAR will be addressed. This work is supported by MSIP of Korea under KSTAR project and NRF of Korea under Contract No. NRF-2012K2A26000443 and NRF-2014M1A7A1A03029865.

  8. Motional Stark effect diagnostics for KSTAR

    NASA Astrophysics Data System (ADS)

    Chung, J.; Ko, J.; Howard, J.; Michael, C.; von Nessi, G.; Thorman, A.; De Bock, M. F. M.

    2014-10-01

    The motional Stark effect (MSE) diagnostic is used to measure the radial magnetic pitch-angle profile in neutral-beam-heated plasmas. The diagnostic relies upon the measurement of the polarization direction of Stark-split D-alpha emission from injected fast neutral atoms in a magnetic field. Measurements of the magnetic pitch angle are used with magnetic equilibrium reconstruction codes such as EFIT to calculate the safety factor in shaped plasmas. The MSE diagnostic is important for determining the shape of the q profile to optimize confinement and stability, and it has become a key element in high-performance tokamaks. For the purpose of achieving the high-performance operating region in the Korea Superconducting Tokamak Advanced Research KSTAR device, two types of methods are being studied. In KSTAR, a multichord PEM (photo-elastic modulator)-based MSE system is being developed, and an imaging MSE polarimetry system using the coherence imaging technique has been showing promising initial results during the last two KSTAR experimental campaigns in 2012 and 2013, respectively. In this paper, we describe the progress of the KSTAR MSE diagnostics.

  9. Search for Suitable ICRF Operation Window for the Shaped H-mode Operation of KSTAR

    SciTech Connect

    Park, B. H.; Kim, J. Y.

    2009-11-26

    KSTAR will try to achieve its 1st shaped H-mode plasma in 2010 campaign. The available power is limited by our plan for auxiliary heating system. Up to 2010, NBI with 1 MW, LHCD 0.5 MW, and ECH with 0.5 MW power will be prepared. To accomplish high beta plasma, TF magnetic field will be reduced to 2 T from rated field of 3.5 T. In this case the ECH contribution to H-mode power threshold requirement is ignorant because the 84 GHz frequency does not meet neither fundamental nor second harmonic resonance in the discharge area. Therefore the ICRF heating should carry out important roll to reach power threshold. The ICRF system of tunable frequency from 30 to 60 MHz will come with 1 MW power in 2010. To maximize the ICRF heating efficiency for H-mode purpose, we try to find suitable condition of ICRF heating parameters through the simulation using by TORIC code. Optimizations of RF frequency, toroidal modes controllable by 4 current straps, and the minority concentration are performed. Possibilities of second harmonic heating of minority and the mode converted heating near resonance layer are also studied.

  10. A Self-consistent Simulation of KSTAR Reverse-shear Operation Mode using ASTRA Code

    NASA Astrophysics Data System (ADS)

    Kim, J. Y.; Jhang, Hogun

    2001-10-01

    A simulation study is presented on the reverse-shear operation mode of KSTAR (Korea Superconducting Tokamak Advanced Research) device, using the ASTRA (Automatic System of TRansport Analysis in a tokamak) code. The heat deposition and the current profile evolution are modeled self-consistently from the ASTRA code into which several heating and current-drive modules of NBI, ICRH/FWCD, and LHCD have been implemented. The anomalous transport is modeled more elaborately by using the theory-based models, such as IFS/PPPL one, rather than conventional empirical or artificial formulas. The effect of equilibrium flow shear and its time evolution are also included in the modeling for a more realistic description of the formation of ITB and its spatial and temporal evolution. Finally, based on the simulation results we will discuss the possible way to get an AT mode plasma with high-beta and high bootstrap current fraction, avoiding a steep pressure gradient and related local MHD instabilities.

  11. Current profile control experiments with LHCD on TdeV

    NASA Astrophysics Data System (ADS)

    Côté, A.; Côté, C.; Demers, Y.; Fuchs, V.; Litaudon, X.; Abel, G.; Lachambre, J.-L.; Mercier, J.-F.; Michaud, D.; Quirion, B.; Shkarofsky, I. P.; Shoucri, M.; St-Onge, M.

    1997-04-01

    Large current profile modifications (-0.4LHCD and ECRH predicts steady state reversed shear.

  12. Study of LHCD efficiency on the FT-2 tokamak

    SciTech Connect

    Lashkul, S. I.; Altukhov, A. B.; Gurchenko, A. D.; Dyachenko, V. V.; Esipov, L. A.; Kantor, M. Yu.; Kouprienko, D. V.; Irzak, M. A.; Saveliev, A. N.; Sidorov, A. V.; Shatalin, S. V.

    2009-11-26

    The paper pays the main attention to the LHCD efficiency in experiments on the FT-2 tokamak. LH wave spectra P(N{sub z}) excited by the grill computed by GRILL3D code are presented. Physical processes responsible for termination of the CD with density rise are discussed for lower and higher plasma currents that are for relatively cold and relatively hot plasmas. A role of parametric processes and additional impurity influx for CD switching-off in the plasma are considered for those conditions.

  13. LHCD experiments in high performance plasmas in JET

    NASA Astrophysics Data System (ADS)

    Ekedahl, A.; Baranov, Y.; Dobbing, J. A.; Fischer, B.; Goniche, M.; Gormezano, C.; Romero, J. A.; Schild, P.; Söldner, F. X.; Challis, C. D.; Sips, A. C. C.; Tubbing, B.

    1997-04-01

    Lower Hybrid Current Drive (LHCD) has been used for current profile shaping in the shear optimisation experiments in 1996/97 in JET. PLH≲3MW has been applied in the initial current ramp-up in order to control the internal inductance. An internal transport barrier with improved central electron confinement has been produced in this phase with LHCD alone. This has resulted in a peaking of the electron temperature profile and Te0 above 10keV at ne0⩽1.5×1019 m-3. The profile of the LH driven current, as determined by hard X-ray mesurements, is peaked at approximately mid-radius in these conditions. Good coupling of the LH waves has been obtained by the use of a near gas feed. This method reduces the risk of plasma-launcher interaction, since the launcher can be positioned in the shadow of the poloidal limiters. A reflection coefficient of 5% has been maintained at a plasma-launcher distance of 8 cm and PLH=5 MW has been coupled to divertor plasmas in L-mode with this method.

  14. 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.

  15. Destabilization of internal kink by LHCD suprathermal electron pressure

    NASA Astrophysics Data System (ADS)

    Delgado-Aparicio, L.; Shiraiwa, S.; Sugiyama, L.; Parker, R.; Granetz, R.; Baek, S.; Mumgaard, R.; Faust, I.; Scott, S.; Gorelenkov, N.; Bertelli, N.; Gao, C.; Greenwald, M.; Hubbard, A.; Hughes, J.; Irby, J.; Marmar, E.; Phillips, P.; Rice, J.; Wallace, G.; Wilson, R.; Wolfe, S.; Wukitch, S.

    2013-10-01

    New observations of the formation of short-lived modes have recently been carried out on Alcator C-Mod. A (1,1) internal kink appears to be destabilized by the fast-electron pressure carried by the suprathermal electrons driven by Lower Hybrid Current Drive (LHCD). Surprisingly, the (1,1) fishbone-like activity can coexist with sawteeth, suggesting that the two modes have independent driving mechanisms. The frequency of the mode is comparable to the core toroidal rotation and that of the precursors. The electron energies responsible for driving the mode have been measured for the first time using the downshift of electron gyrofrequency due to relativistic effects. This is a new explanation for the so-called electron-fishbones. This work was performed under US DoE contracts DE-FC02-99ER54512, DE-AC02-09CH11466 and DE-FG03-96ER-54373.

  16. Sawtooth-Stabilization and Snake-Excitation during LHCD on the HL-1M

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Qiu, Xiao-Ming; Dong, Yun-Bo; Guo, Gan-Cheng; Zhong, Yun-Ze; Fu, Bing-Zhong; Liu, Yong

    2004-02-01

    Lower-hybrid current drive (LHCD) experiments were carried out in the HL-1M hydrogen plasmas. The suppression of sawtooth instabilities by LHCD has been observed in the sawtoothing discharges; an improvement in the global energy confinement time of up to 20% is observed. There is an optimal rf-power range for the complete suppression of the central MHD instabilities. Possible mechanisms for the stabilization of the sawtooth instability are discussed from the measurement of internal inductance and current profile reconstruction using an equilibrium code. A large long-lived snake-like oscillation is newly observed at the end of the sawtooth-stabilization phase of the LHCD operation in the HL-1M tokamak. It is evident that such perturbation is due to a temperature depression caused by impurity accumulation during LHCD.

  17. Control of Internal Profiles via LHCD on Alcator C-Mod

    SciTech Connect

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

    2009-11-26

    LHCD on Alcator C-Mod is being used in plasmas with parameters similar to those expected on ITER for the purpose of tailoring the plasma current profile. LHCD experiments have also produced intriguing results related to momentum transport and edge pedestal physics that affect the toroidal rotation profile and the temperature and density profiles. Quantitative comparisons between local measurements and theory/simulation have been performed, confirming the off-axis localization of the current drive, as well as its magnitude and location dependence on the launched n{sub parallel} spectrum and electron temperature. Applying LHCD during the current ramp saves volt-seconds and delays the peaking of the current profile. Counter current toroidal rotation during LHCD has been observed in both L and H-mode plasmas. In H-mode plasmas the edge pedestal collisionality is reduced while the overall pressure in the pedestal increases slightly.

  18. Scaling of Global LHCD Efficiency in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Scott, S.; Bonoli, P.; Mumgaard, R.; Shiraiwa, S.; Wallace, G.; Whyte, D.

    2014-10-01

    A database of global current-drive efficiency by Lower Hybrid waves has been assembled covering nine years of C-Mod operation. Plasma conditions were averaged over 50-ms time slices during equilibrated current-profile time periods, excluding transient events such as Prad spikes. The database comprises 1800 time slices spanning: PLH < 1 . 1 MW, n|| = 1.5-2.3, Ip = 0.3-1.0 MA, nebar = 0.35-1.5 e20. Nine percent of the data points are approximately non-inductive (ΔV/V >0.9), while 17 percent experience low m,n MHD that degrades the LHCD efficiency. During LHCD, a simple Spitzer model is used to estimate the residual inductively-driven current which scales the pre-LH current by the ratio of the loop voltage to the pre-LH loop voltage, correcting also for the change in conductivity. The current-drive efficiency is defined as η = nebar R ILHCD /PLH [1020 MA/m2 MW], where ILHCD is the current driven by LH waves and PLH is the forward-directed LH power. In approximately non-inductive, MHD-free plasmas, the global current drive efficiency shows a striking positive correlation with plasma current, η = 0.065 + 0.40 x Ip [MA], reaching a value of η = 0.47 at Ip =1.02 MA. A positive but weaker correlation between η and Teo does not explain the η dependence on Ip. Preliminary GENRAY/CQL3D simulations at Ip =1.0 MA predict 900 kA of driven current versus 1000 kA observed. Comparisons of η to numerical simulations over a wide parameter range will be discussed. Work supported by DoE Awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  19. 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.

  20. Phillips SA8016BW 2.5 GHz Synthesizer SEE Testing

    NASA Technical Reports Server (NTRS)

    Carts, Marty; Ladbury, Ray; Marshall, Paul W.; Mackey, Susan

    2008-01-01

    This viewgraph presentation reviews the Single Event Effects (SEE) testing of the Phillips SA8016BW 2.5 GHz Synthesizer that was chose by the GLAST Program for Frequency Generation. Included in this are diagrams of the phased-locked loop (PLL), the synthesizer, and heater.

  1. Space VLBI observations of 3C 279 at 1.6 and 5 GHz

    NASA Technical Reports Server (NTRS)

    Piner, B. G.; Edwards, P. G.; Wehrle, A. E.; Hirabayashi, H.; Lovell, J. E.; Unwin, S. C.

    2000-01-01

    We present VLBI Space Observatory Programme (VSOP) observations of the gamma-ray blazar 3C 279 at 1.6 and 5 GHz made on 1998 January 9-10 with the HALCA satellite and ground arrays including the Very Long Baseline Array (VLBA).

  2. 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.

  3. 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.

  4. ECH-assisted startup at KSTAR

    SciTech Connect

    Bae, Y. S.; Joung, M.; Yoon, S. W.; Kim, J. H.; Hahn, S. H.; Kim, W. C.; Yang, H. L.; Oh, Y. K.; Bak, J. S.; Kwon, M.; Jeong, J. H.; Park, S. I.; Cho, M. H.; Namkung, W.; Jackson, G. L.; Humphreys, D.; Walker, M. L.; Gorelov, Y.; Leuer, J. A.; Hyatt, A. W.

    2009-11-26

    The electron cyclotron heating (ECH)-assisted startup was successful in the Korea Superconducting Tokamak Advanced Research (KSTAR) first plasma campaign completed in June, 2008. It was observed that the second harmonic EC wave of 0.35 MW was sufficient to achieve breakdown in the ECH pre-ionization phase, to allow burn through, and to sustain the plasma during the current ramp with a low loop voltage of 2.0 V. This corresponds to a toroidal electric field of 0.24 Vm{sup -1} at the innermost vacuum vessel wall (R = 1.3 m). Since there is no feedback control of the plasma radial position in the initial phase of the KSTAR first plasma campaign, wall contact caused the plasma current fall to zero soon after the ECH beam was turned off. Extending pulse duration of the ECH power to 190 ms allowed the plasma current to rise up to more than 100 kA with a ramp-up rate of 0.8 MA/s and the pulse duration of 210 ms. Later in the first plasma campaign, the plasma was sustained up to 865 ms with the help of additional heating of 350-ms long ECH beam and with the help of the plasma radial position feedback control. The plasma current in the pre-ionization phase was observed and it is considered to be pressure-driven Pfirsch-Schlueter current.

  5. Observations of tropospheric phase scintillations at 5 GHz on vertical paths

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.; Sramek, R. A.

    1982-01-01

    The article presents observations of turbulence-induced tropospheric phase fluctuations measured at 5 GHz on the near-vertical paths relevant to many astronomical and geophysical measurements. The data are summarized as phase power spectra, structure functions, and Allan variances. Comparisons to other microwave observations indicate relatively good agreement in both the level and shape of the power spectrum of these tropospheric phase fluctuations. Implications for precision Doppler tracking of spacecraft and geodesy/radio interferometry are discussed.

  6. VizieR Online Data Catalog: VSOP 5GHz AGN survey V. (Dodson+, 2008)

    NASA Astrophysics Data System (ADS)

    Dodson, R.; Fomalont, E. B.; Wiik, K.; Horiuchi, S.; Hirabayashi, H.; Edwards, P. G.; Murata, Y.; Asaki, Y.; Moellenbrock, G. A.; Scott, W. K.; Taylor, A. R.; Gurvits, L. I.; Paragi, Z.; Frey, S.; Shen, Z.-Q.; Lovell, J. E. J.; Tingay, S. J.; Rioja, M. J.; Fodor, S.; Lister, M. L.; Mosoni, L.; Coldwell, G.; Piner, B. G.; Yang, J.

    2009-08-01

    The VSOP mission and the 5GHz AGN Survey are fully discussed in Hirabayashi et al. (1998Sci...281.1825H, 2000PASJ...52..955H), Paper I (Hirabayashi et al., 2000, Cat J/PASJ/52/997), and Fomalont et al. (2000, Cat. J/ApJS/131/95). Observations began in 1997 August, with the final observations being made in 2003 October. Of the VSS sample of 294 sources, all but 29 were observed. (3 data files).

  7. Development of frequency step tunable 1 MW gyrotron at 131 to 146.5 GHz

    SciTech Connect

    Samartsev, A.; Gantenbein, G.; Dammertz, G.; Illy, S.; Kern, S.; Leonhardt, W.; Schlaich, A.; Schmid, M.; Thumm, M.

    2011-07-01

    Effective control of power absorption in tokamaks and stellarators could be achieved by the frequency tuning of ECH and CD power delivered by high-power gyrotrons. In this report some results of the development of a frequency tunable gyrotron with fused-silica Brewster window are presented. Excitation of several modes at 1 MW power level in the range of frequencies from 131 to 146.5 GHz is achieved. (author)

  8. Behaviour of runaway electrons in the HL-2A plasmas with LHCD and ECCD

    NASA Astrophysics Data System (ADS)

    Zhu, J. X.; Yao, L. M.; Zhang, Y. P.; Yang, J. W.; Yang

    2015-12-01

    > The behaviour of runaway electrons have been investigated in lower hybrid current drive (LHCD) and electron cyclotron current drive (ECCD) plasmas as well as the LHCD only plasmas in the HL-2A tokamak. The fast electrons generated by lower hybrid waves (LHWs) and electron cyclotron waves (ECWs) can act as a seed population for runaway electrons. In the LHCD only discharges, a large number of runaway electrons are produced after the termination of lower hybrid (LH) power by conversion of fast electrons into runaway electrons due to the fast electron tail which extends above the runaway critical energy. However, in contrast to LHCD only discharges, during the simultaneous application of LHCD and ECCD discharges, runaway electrons cannot be created by the termination of LH power when the ECCD is on duty. The runaway production is observed to be enhanced until the EC power termination. The loop voltage increase due to the termination of EC power gives rise to a decline in the critical runaway energy, which leads to some of the energetic fast electrons converting into runaway electrons via the acceleration from the toroidal electric field. That is, the fast electrons created by waves can be accelerated into the runaway regime due to the Dreicer process.

  9. 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.

  10. The ATLAS 5.5 GHz survey of the extended Chandra Deep Field South: the second data release

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    We present a new image of the 5.5 GHz radio emission from the extended Chandra Deep Field South. Deep radio observations at 5.5 GHz were obtained in 2010 and presented in the first data release. A further 76 h of integration has since been obtained, nearly doubling the integration time. This paper presents a new analysis of all the data. The new image reaches 8.6 μJy rms, an improvement of about 40 per cent in sensitivity. We present a new catalogue of 5.5 GHz sources, identifying 212 source components, roughly 50 per cent more than were detected in the first data release. Source counts derived from this sample are consistent with those reported in the literature for S5.5 GHz > 0.1 mJy but significantly lower than published values in the lowest flux density bins (S5.5 GHz < 0.1 mJy), where we have more detected sources and improved statistical reliability. The 5.5 GHz radio sources were matched to 1.4 GHz sources in the literature and we find a mean spectral index of -0.35 ± 0.10 for S5.5 GHz > 0.5 mJy, consistent with the flattening of the spectral index observed in 5 GHz sub-mJy samples. The median spectral index of the whole sample is αmed = -0.58, indicating that these observations may be starting to probe the star-forming population. However, even at the faintest levels (0.05 < S5.5 GHz < 0.1 mJy), 39 per cent of the 5.5 GHz sources have flat or inverted radio spectra. Four flux density measurements from our data, across the full 4.5-6.5 GHz bandwidth, are combined with those from literature and we find 10 per cent of sources (S5.5 GHz ≳ 0.1 mJy) show significant curvature in their radio spectral energy distribution spanning 1.4-9 GHz.

  11. 2.5 GHz integrated graphene RF power amplifier on SiC substrate

    NASA Astrophysics Data System (ADS)

    Hanna, T.; Deltimple, N.; Khenissa, M. S.; Pallecchi, E.; Happy, H.; Frégonèse, S.

    2017-01-01

    In this work, we report the design of 2.5 GHz integrated power amplifier based on a graphene FET fabricated with thermal deposition on SiC. In this first large signal study of graphene radiofrequency power amplifiers, a power gain of 8.9 dB is achieved, the maximum reported output power and power added efficiency are 5.1 dBm and 2.2% respectively. Furthermore, graphene and Si CMOS amplifiers are compared; conclusions are drawn towards the technology enhancements to optimize the amplifiers figures of merit.

  12. 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.

  13. Impact of isotopic effect on density limit and LHCD efficiency in the FT-2 experiments

    NASA Astrophysics Data System (ADS)

    Lashkul, S. I.; Altukhov, A. B.; Gurchenko, A. D.; Gusakov, E. Z.; Dyachenko, V. V.; Esipov, L. A.; Irzak, M. A.; Kantor, M. Yu.; Kouprienko, D. V.; Perevalov, A. A.; Saveliev, A. N.; Shatalin, S. V.; Stepanov, A. Yu.

    2015-07-01

    Current drive by lower hybrid waves (LHCD) is the most effective method to sustain the plasma current, but it is feasible only at the plasma density not exceeding some density limit nDL. In the present work the main attention is paid to the investigation of this effect on the FT-2 (R = 0.55 m, a = 0.08 m, BT ⩽ 3 T, Ipl = 19-40 kA, f0 = 920 MHz) tokamak. The dependence of LHCD efficiency on isotopic plasma content (hydrogen/deuterium) is studied. Characteristic features of such an experiment are a strong influence of the isotope plasma composition on the LH resonance density nLH. For hydrogen plasma nLH ≈ 3.5 × 1019 m-3, while for deuterium plasma nLH ≈ 2 × 1020 m-3. The suppression of the LHCD and beginning of the interaction of LH waves with ions are determined by the hydrogen/deuterium plasma density rise. In the hot hydrogen plasma (Te(r = 0 cm) ≈ 700 eV) the density limit nDL of LHCD is approximately equal to the resonance value nLH ≈ nLC, where nLC is the point of linear conversion. In the hot deuterium plasma one could expect an increase of nDL because of a much higher value of nLH ⩾ nLC ≈ 1020 m-3. However it appeared that the observed density limit for LHCD generation nDL ≈ (3.5-4) × 1019 m-3 is not determined by nLH. The role of parametric instabilities in CD switch-off is considered in both cases. The cooling of the plasma column and density rise could lead to a reduction of the threshold for the parametric decay of f0 and result in early suppression of LHCD. In both cases the LHCD was inversely proportional to the density, which corresponds to the theoretical predictions. In order to analyse the experimentally observed LHCD efficiency the GRILL3D and FRTC codes have been used.

  14. 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

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

    SciTech Connect

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

    2016-09-15

    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.

  16. 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.

  17. Control simulation of neoclassical tearing modes in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Hwang, Y. S.

    2006-10-01

    Control of neoclassical tearing modes (NTMs) is one of the key issues to achieve stable high performance discharges for future advanced tokamaks. In KSTAR, active suppression of m/n = 3/2 and 2/1 NTMs will be pursued by using a 3MW electron cyclotron current drive (ECCD) system. To develop a NTM control system in KSTAR, a prototype NTM control simulator is developed. A NTM stability model is constructed by the modified Rutherford equation (MRE) with KSTAR equilibrium parameters. In the NTM controller, the plasma radial position is controlled to align the ECCD to the resonant flux surface where the tearing mode resides by utilizing the fast in-vessel control coils (IVCCs) of KSTAR. To model radial plasma responses during the control sequence, a linear, non-rigid plasma model is constructed by following perturbed equilibrium formulation. Performance of the prototype simulator is assessed in terms of suppressing the NTM modes in KSTAR and utilized to provide controller design criteria for the complete suppression of the modes. The prototype simulator will be used to develop a new NTM control algorithm for the model-based advanced controller with high control efficiency.

  18. Criteria for Neoclassical Tearing Modes Suppression in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Hwang, Y. S.

    2007-11-01

    In KSTAR, neoclassical tearing modes(NTMs) will be suppressed by using 170GHz electron cyclotron current drive(ECCD) system with steering mirrors that align the current deposition to NTM locations. As an initial stage of NTM suppression study, 1 MW ECCD power will be used to suppress m/n = 3/2 and 2/1 NTMs. To confirm the feasibility of successful suppression of the modes under the proposed KSTAR environment, modified Rutherford equation(MRE) which encapsulates stability of NTMs is constructed for the target equilibrium of KSTAR. The geometric coefficients in MRE are obtained by comparing saturated sizes of NTMs from ISLAND code [1] with the amounts of local bootstrap currents from ONETWO. Parameters related to the operation of ECCD are analyzed by TORAY-GA linear ray-tracing code. Due to the small ECCD power available at the initial stage of KSTAR, condition of the optimum ECCD modulation is considered in the analysis to maximize suppression performance. From the analyses, criteria such as the minimum ECCD power required for complete suppression of the modes and the optimum conditions of EC wave launch angle and modulation duty factor are derived for the successful NTM suppression in KSTAR. [1] C.N. Nguyen, G. Bateman and A.H. Kritz, Phys. Plasmas 11 3460 (2004)

  19. 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.

  20. 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.

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

    SciTech Connect

    Lee, J. H. Ko, W. H.; Oh, S.; Lee, W. R.; 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.

    2014-11-15

    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.

  2. Design of practical alignment device in KSTAR Thomson diagnostic

    SciTech Connect

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

    2016-11-15

    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.

  3. 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

  4. Diamagnetic loop for the first plasma in the KSTAR machine.

    PubMed

    Bak, J G; Lee, S G; Ka, E M

    2008-10-01

    The diamagnetic loop (DL) is installed for the plasma diamagnetic measurement at the first plasma in the Korea superconducting tokamak advanced research (KSTAR) machine. Experimental results from the position measurement of the DL inside the KSTAR vacuum vessel and the vacuum flux measurement by using the DL for the evaluation of the geometrical data and the balance coefficient of the DL for the compensation of the vacuum flux in the diamagnetic measurement are described. In addition, a preliminary work of an instrument for a hardware compensation of the vacuum flux is presented.

  5. Diamagnetic loop for the first plasma in the KSTAR machine

    SciTech Connect

    Bak, J. G.; Lee, S. G.; Ka, E. M.

    2008-10-15

    The diamagnetic loop (DL) is installed for the plasma diamagnetic measurement at the first plasma in the Korea superconducting tokamak advanced research (KSTAR) machine. Experimental results from the position measurement of the DL inside the KSTAR vacuum vessel and the vacuum flux measurement by using the DL for the evaluation of the geometrical data and the balance coefficient of the DL for the compensation of the vacuum flux in the diamagnetic measurement are described. In addition, a preliminary work of an instrument for a hardware compensation of the vacuum flux is presented.

  6. Isotopic effect study in the LHCD and LHH experiments in hydrogen/deuterium plasmas of the FT-2 tokamak

    SciTech Connect

    Lashkul, S. I.; Altukhov, A. B.; Gusakov, E. Z.; Dyachenko, V. V.; Esipov, L. A.; Irzak, M. A.; Kantor, M. Yu.; Kouprienko, D. V.; Saveliev, A. N.; Shatalin, S. V.; Stepanov, A. Yu.

    2014-02-12

    Results of comparative experimental studies of the efficiency of lower hybrid current drive (LHCD) and lower hybrid heating (LHH) in the FT-2 tokamak in hydrogen and deuterium plasmas are presented. In the new comparative experimental runs in deuterium/hydrogen plasmas suppression of the LHCD and beginning of the interaction of LH waves with ions is controlled by the plasma density rise. Role of parametric instabilities in CD switch-off is considered. In order to analyze the experimentally observed effect of LHCD the GRILL3D and FRTC codes has been used.

  7. The VSOP 5 GHz Active Galactic Nucleus Survey. V. Imaging Results for the Remaining 140 Sources

    NASA Astrophysics Data System (ADS)

    Dodson, R.; Fomalont, E. B.; Wiik, K.; Horiuchi, S.; Hirabayashi, H.; Edwards, P. G.; Murata, Y.; Asaki, Y.; Moellenbrock, G. A.; Scott, W. K.; Taylor, A. R.; Gurvits, L. I.; Paragi, Z.; Frey, S.; Shen, Z.-Q.; Lovell, J. E. J.; Tingay, S. J.; Rioja, M. J.; Fodor, S.; Lister, M. L.; Mosoni, L.; Coldwell, G.; Piner, B. G.; Yang, J.

    2008-04-01

    In 1997 February, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Program (VSOP) mission. Approximately 25% of the mission time was dedicated to the VSOP survey of bright compact active galactic nuclei (AGNs) at 5 GHz. This paper, the fifth in the series, presents images and models for the remaining 140 sources not included in the third paper in the series, which contained 102 sources. For most sources, the plots of the (u,v) coverage, the visibility amplitude versus (u,v) distance, and the high-resolution image are presented. Model fit parameters to the major radio components are determined, and the brightness temperature of the core component for each source is calculated. The brightness temperature distributions for all of the sources in the VSOP AGN survey are discussed.

  8. 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.

  9. 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.

  10. 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.

  11. Fluxon induced surface resistance and field emission in niobium films at 1.5 GHz

    NASA Astrophysics Data System (ADS)

    Benvenuti, C.; Calatroni, S.; Darriulat, P.; Peck, M. A.; Valente, A.-M.; Van't Hof, C. A.

    2001-08-01

    The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resistance proportional to the density of the fluxon lattice and increasing linearly with the amplitude of the microwave above a threshold significantly lower than the field emission threshold. Such an effect, precursor of electron emission, is observed here for the first time in a study using radiofrequency cavities operated at their fundamental 1.5 GHz frequency. The measured properties of the additional surface resistance severely constrain possible explanations of the observed effect.

  12. Precise Absolute Astrometry from the VLBA Imaging and Polarimetry Survey at 5 GHz

    NASA Technical Reports Server (NTRS)

    Petrov, L.; Taylor, G. B.

    2011-01-01

    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.

  13. 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.

  14. Progress and plan of KSTAR plasma control system upgrade

    DOE PAGES

    Hahn, Sang-hee; Kim, Y. J.; Penaflor, B. G.; ...

    2016-06-01

    The plasma control system (PCS) has been one of essential systems in annual KSTAR plasma campaigns: starting from a single-process version in 2008, extensive upgrades are done through the previous 7 years in order to achieve major goals of KSTAR performance enhancement. Here, major implementations are explained in this paper. In consequences of successive upgrades, the present KSTAR PCS is able to achieve ~48 s of 500 kA plasma pulses with full real-time shaping controls and real-time NB power controls. It has become a huge system capable of dealing with 8 separate categories of algorithms, 26 actuators directly controllable duringmore » the shot, and real-time data communication units consisting of +180 analog channels and +600 digital input/outputs through the reflective memory (RFM) network. The next upgrade of the KSTAR PCS is planned in 2015 before the campaign. An overview of the upgrade layout will be given for this paper. The real-time system box is planned to use the CERN MRG-Realtime OS, an ITER-compatible standard operating system. New hardware is developed for faster real-time streaming system for future installations of actuators/diagnostics.« less

  15. New ion source for KSTAR neutral beam injection system.

    PubMed

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

    2012-02-01

    The neutral beam injection system (NBI-1) of the KSTAR tokamak can accommodate three ion sources; however, it is currently equipped with only one prototype ion source. In the 2010 and 2011 KSTAR campaigns, this ion source supplied deuterium neutral beam power of 0.7-1.6 MW to the KSTAR plasma with a beam energy of 70-100 keV. A new ion source will be prepared for the 2012 KSTAR campaign with a much advanced performance compared with the previous one. The newly designed ion source has a very large transparency (∼56%) without deteriorating the beam optics, which is designed to deliver a 2 MW injection power of deuterium beams at 100 keV. The plasma generator of the ion source is of a horizontally cusped bucket type, and the whole inner wall, except the cathode filaments and plasma grid side, functions as an anode. The accelerator assembly consists of four multi-circular aperture grids made of copper and four electrode flanges made of aluminum alloy. The electrodes are insulated using PEEK. The ion source will be completed and tested in 2011.

  16. 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).

  17. Progress and plan of KSTAR plasma control system upgrade

    SciTech Connect

    Hahn, Sang-hee; Kim, Y. J.; Penaflor, B. G.; Bak, J. G.; Han, H.; Hong, J. S.; Jeon, Y. M.; Jeong, J. H.; Joung, M.; Juhn, J. W.; Kim, J. S.; Kim, H. S.; Lee, W. R.; Woo, M. H.; Eidietis, N. W.; Ferron, J. R.; Humphreys, D. A.; Hyatt, A.; Johnson, R. D.; Piglowski, D. A.; Walker, M. L.; Welander, A. S.; Mueller, D.; Milne, P. G.

    2016-06-01

    The plasma control system (PCS) has been one of essential systems in annual KSTAR plasma campaigns: starting from a single-process version in 2008, extensive upgrades are done through the previous 7 years in order to achieve major goals of KSTAR performance enhancement. Here, major implementations are explained in this paper. In consequences of successive upgrades, the present KSTAR PCS is able to achieve ~48 s of 500 kA plasma pulses with full real-time shaping controls and real-time NB power controls. It has become a huge system capable of dealing with 8 separate categories of algorithms, 26 actuators directly controllable during the shot, and real-time data communication units consisting of +180 analog channels and +600 digital input/outputs through the reflective memory (RFM) network. The next upgrade of the KSTAR PCS is planned in 2015 before the campaign. An overview of the upgrade layout will be given for this paper. The real-time system box is planned to use the CERN MRG-Realtime OS, an ITER-compatible standard operating system. New hardware is developed for faster real-time streaming system for future installations of actuators/diagnostics.

  18. Simulations of KSTAR high performance steady state operation scenarios

    NASA Astrophysics Data System (ADS)

    Na, Yong-Su; Kessel, C. E.; Park, J. M.; Yi, Sumin; Becoulet, A.; Sips, A. C. C.; Kim, J. Y.

    2009-11-01

    We report the results of predictive modelling of high performance steady state operation scenarios in KSTAR. Firstly, the capabilities of steady state operation are investigated with time-dependent simulations using a free-boundary plasma equilibrium evolution code coupled with transport calculations. Secondly, the reproducibility of high performance steady state operation scenarios developed in the DIII-D tokamak, of similar size to that of KSTAR, is investigated using the experimental data taken from DIII-D. Finally, the capability of ITER-relevant steady state operation is investigated in KSTAR. It is found that KSTAR is able to establish high performance steady state operation scenarios; βN above 3, H98(y, 2) up to 2.0, fBS up to 0.76 and fNI equals 1.0. In this work, a realistic density profile is newly introduced for predictive simulations by employing the scaling law of a density peaking factor. The influence of the current ramp-up scenario and the transport model is discussed with respect to the fusion performance and non-inductive current drive fraction in the transport simulations. As observed in the experiments, both the heating and the plasma current waveforms in the current ramp-up phase produce a strong effect on the q-profile, the fusion performance and also on the non-inductive current drive fraction in the current flattop phase. A criterion in terms of qmin is found to establish ITER-relevant steady state operation scenarios. This will provide a guideline for designing the current ramp-up phase in KSTAR. It is observed that the transport model also affects the predictive values of fusion performance as well as the non-inductive current drive fraction. The Weiland transport model predicts the highest fusion performance as well as non-inductive current drive fraction in KSTAR. In contrast, the GLF23 model exhibits the lowest ones. ITER-relevant advanced scenarios cannot be obtained with the GLF23 model in the conditions given in this work. Finally

  19. Simulations of KSTAR high performance steady state operation scenarios

    SciTech Connect

    Na, Y S; Kessel, C. E.; Park, Jin Myung; Yi, Sumin; Becoulet, A.; Sips, A C C; Kim, J Y

    2009-01-01

    We report the results of predictive modelling of high performance steady state operation scenarios in KSTAR. Firstly, the capabilities of steady state operation are investigated with time-dependent simulations using a free-boundary plasma equilibrium evolution code coupled with transport calculations. Secondly, the reproducibility of high performance steady state operation scenarios developed in the DIII-D tokamak, of similar size to that of KSTAR, is investigated using the experimental data taken from DIII-D. Finally, the capability of ITER-relevant steady state operation is investigated in KSTAR. It is found that KSTAR is able to establish high performance steady state operation scenarios; beta(N) above 3, H-98(y, 2) up to 2.0, f(BS) up to 0.76 and f(NI) equals 1.0. In this work, a realistic density profile is newly introduced for predictive simulations by employing the scaling law of a density peaking factor. The influence of the current ramp-up scenario and the transport model is discussed with respect to the fusion performance and non-inductive current drive fraction in the transport simulations. As observed in the experiments, both the heating and the plasma current waveforms in the current ramp-up phase produce a strong effect on the q-profile, the fusion performance and also on the non-inductive current drive fraction in the current flattop phase. A criterion in terms of q(min) is found to establish ITER-relevant steady state operation scenarios. This will provide a guideline for designing the current ramp-up phase in KSTAR. It is observed that the transport model also affects the predictive values of fusion performance as well as the non-inductive current drive fraction. The Weiland transport model predicts the highest fusion performance as well as non-inductive current drive fraction in KSTAR. In contrast, the GLF23 model exhibits the lowest ones. ITER-relevant advanced scenarios cannot be obtained with the GLF23 model in the conditions given in this work

  20. A 15 GSa/s, 1.5 GHz bandwidth waveform digitizing ASIC

    NASA Astrophysics Data System (ADS)

    Oberla, Eric; Genat, Jean-Francois; Grabas, Hervé; Frisch, Henry; Nishimura, Kurtis; Varner, Gary

    2014-01-01

    The PSEC4 custom integrated circuit was designed for the recording of fast waveforms for use in large-area time-of-flight detector systems. The ASIC has been fabricated using the IBM-8RF 0.13 μm CMOS process. On each of the six analog channels, PSEC4 employs a switched capacitor array (SCA) of 256 samples deep, a ramp-compare ADC with 10.5 bits of DC dynamic range, and a serial data readout with the capability of region-of-interest windowing to reduce dead time. The sampling rate can be adjusted between 4 and 15 Gigasamples/second (GSa/s) on all channels and is servo-controlled on-chip with a low-jitter delay-locked loop (DLL). The input signals are passively coupled on-chip with a -3 dB analog bandwidth of 1.5 GHz. The power consumption in quiescent sampling mode is less than 50 mW/chip; at a sustained trigger and a readout rate of 50 kHz the chip draws 100 mW. After fixed-pattern pedestal subtraction, the uncorrected integral non-linearity is 0.15% over a 750 mV dynamic range. With a linearity correction, a full 1 V signal voltage range is available. The sampling timebase has a fixed-pattern non-linearity with an RMS of 13%, which can be corrected for precision waveform feature extraction and timing.

  1. Study of the surface resistance of superconducting niobium films at 1.5 GHz

    NASA Astrophysics Data System (ADS)

    Benvenuti, C.; Calatroni, S.; Campisi, I. E.; Darriulat, P.; Peck, M. A.; Russo, R.; Valente, A.-M.

    1999-05-01

    A systematic study of superconducting properties of niobium films sputtered on the inner wall of radiofrequency cavities is presented. The measured quantities include in particular the response to 1.5 GHz microwaves, the critical temperature, the penetration depth and the magnetic penetration field. In addition to films grown in different gas discharges (Xe, Kr, Ar and Ar/Ne mixtures) and to films grown on substrates prepared under different conditions, the study also includes bulk niobium cavities. The surface resistance is analysed in terms of its dependence on temperature, on RF field and, when relevant, on the density of trapped fluxons. A simple parameterisation is found to give a good fit to the data. Once allowance for the presence of impurities and defects is made by means of a single parameter, the electron mean free path, good agreement with BCS theory is observed. The fluxon-induced losses are studied in detail and their dependence on RF field, on temperature and on the density of trapped fluxons is analysed. The residual resistance is observed to be essentially uncorrelated with the other variables, suggesting that it is dominantly extragranular. In occasions very low residual resistances, in the nΩ range, have been maintained over a broad range of RF field, indicating the absence of significant fundamental limitations specific to the film technology in practical applications such as the production of accelerating cavities for particle accelerators.

  2. A stabilized laser continuously tunable over a range of 1.5 GHz

    NASA Astrophysics Data System (ADS)

    Fan, B. L.; Xiong, W.; Wang, S. G.; Wang, L. J.

    2016-11-01

    We demonstrate a method to stabilize laser frequency which can be continuously tuned over a range of 1.5 GHz. It is based on saturated absorption spectroscopy (SAS) generated by an external-cavity diode laser (ECDL) which is modulated by an electro-optic amplitude modulator (EO-AM). The spectra consist of not only the original peaks corresponding to resonant and crossover lines of 133Cs D2 line, but also signals introduced by sidebands from an EO-AM. Thus, the laser frequency can be locked to any point within the range of the spectra. Furthermore, the tuning range of the laser can be doubled compared to the coverage of common SAS by fixing the frequency of the pumping laser. The best stability of the locked laser induced by the EO-AM is 1.27 × 10-11 over an integrating time of 125 s. This method may be applied for more precise and flexible manipulation of atoms and molecules.

  3. A stabilized laser continuously tunable over a range of 1.5 GHz.

    PubMed

    Fan, B L; Xiong, W; Wang, S G; Wang, L J

    2016-11-01

    We demonstrate a method to stabilize laser frequency which can be continuously tuned over a range of 1.5 GHz. It is based on saturated absorption spectroscopy (SAS) generated by an external-cavity diode laser (ECDL) which is modulated by an electro-optic amplitude modulator (EO-AM). The spectra consist of not only the original peaks corresponding to resonant and crossover lines of (133)Cs D2 line, but also signals introduced by sidebands from an EO-AM. Thus, the laser frequency can be locked to any point within the range of the spectra. Furthermore, the tuning range of the laser can be doubled compared to the coverage of common SAS by fixing the frequency of the pumping laser. The best stability of the locked laser induced by the EO-AM is 1.27 × 10(-11) over an integrating time of 125 s. This method may be applied for more precise and flexible manipulation of atoms and molecules.

  4. A 17.5-GHz 3-bit phase-shift receive MMIC - Fabrication and test results

    NASA Astrophysics Data System (ADS)

    Gupta, Aditya K.; Korpinen, Errol V.; Chen, Andy D.; Matthews, David S.

    1990-05-01

    A high-yield, FET gate fabrication technology is described. The main advantage of this processing approach is that it permits fabrication of devices with gate lengths of less than 0.5 micron using standard optical photolithography without recourse to deep UV or electron-beam lithography. The process is simple and easy to implement in a manufacturing environment. Exceptionally good gate-length control, typically 10 percent for a 0.4-micron-long gate, is demonstrated. Yield of a 300-micron-wide FET, designed for use in a gain block and in a switch, is found to be 89 percent on average. Data on wafer-to-wafer and on-wafer variations in device DC and RF parameters and equivalent circuit values are presented. Typical standard deviations are in the 5-10 percent range. This process technology has been used to fabricate a 17.5-GHz, 3-b phase-shift receive monolithic microwave integrated circuit (MMIC) of moderately high complexity. Statistics of RF data on 704 such devices, fabricated over a period of two years, are presented. It is shown that such MMICs can be fabricated with yields sufficient for prototype active phased-array antenna applications.

  5. The Fan Region at 1.5 GHz with GMIMS: Polarized synchrotron emission tracing Galactic structure

    NASA Astrophysics Data System (ADS)

    Hill, Alex S.; Landecker, Tom; Carretti, Ettore; Douglas, Kevin A.; Sun, Xiaohui; Gaensler, Bryan M.; Mao, Sui Ann; McClure-Griffiths, Naomi; Reich, Wolfgang; Wolleben, Maik; Miller Dickey, John; Gray, Andrew; Haverkorn, Marijke; Leahy, John Patrick; Schnitzeler, Dominic

    2017-01-01

    Diffuse polarized radio continuum emission provides information about the structure of the Galactic magnetic field. With the Global Magneto-Ionic Medium Survey (GMIMS), we are mapping this emission from the entire sky from 300 to 1800 MHz. We will present a brief overview of the GMIMS survey.We will focus on 1270-1750 MHz observations from the Northern hemisphere GMIMS data to determine the geometry of the magnetic field in the Fan Region. The Fan Region is one of the dominant features of the sky in polarized radio continuum, long thought to be a local (d < 500 pc) synchrotron emission feature. We find that the 1.5 GHz polarized radio emission is anti-correlated with Halpha emission from the Perseus Arm, 2 kpc away. This indicates that ionized gas in the Perseus Arm depolarizes about 30% of the Fan Region emission, indicating that some of the Fan Region emission originates in or beyond the Perseus Arm. The synchrotron emission must therefore be produced along a large path length, suggesting the presence of a coherent magnetic field in the plane in the outer Galaxy. We argue that the polarized emission from the Fan Region is a consequence of the structure of the Galactic magnetic field and ISM. We model beam depolarization due to the ISM, finding that in the presence of depolarization the rotation measure measured from polarized emission is much lower than that measured towards background point sources, explaining an observed discrepancy between the GMIMS rotation measures and background rotation measures.

  6. 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.

  7. Transport modeling of L- and H-mode discharges with LHCD on EAST

    NASA Astrophysics Data System (ADS)

    Li, M. H.; Ding, B. J.; Imbeaux, F.; Decker, J.; Zhang, X. J.; Kong, E. H.; Zhang, L.; Wei, W.; Shan, J. F.; Liu, F. K.; Wang, M.; Xu, H. D.; Yang, Y.; Peysson, Y.; Basiuk, V.; Artaud, J.-F.; Yuynh, P.; Wan, B. N.

    2013-04-01

    High-confinement (H-mode) discharges with lower hybrid current drive (LHCD) as the only heating source are obtained on EAST. In this paper, an empirical transport model of mixed Bohm/gyro-Bohm for electron and ion heat transport was first calibrated against a database of 3 L-mode shots on EAST. The electron and ion temperature profiles are well reproduced in the predictive modeling with the calibrated model coupled to the suite of codes CRONOS. CRONOS calculations with experimental profiles are also performed for electron power balance analysis. In addition, the time evolutions of LHCD are calculated by the C3PO/LUKE code involving current diffusion, and the results are compared with experimental observations.

  8. Modification of Boundary Parameters and Fluctuations by IBW and LHCD in the HT-7 Tokamak

    NASA Astrophysics Data System (ADS)

    Song, Mei; Wan, Baonian; Xu, Guosheng; Liu, Haiqing; Ling, Bili; Li, Chengfu; Zhou, Liwu

    2003-08-01

    Measurements of boundary parameters and their fluctuations have been performed in ohmic (OH) plasma and Ion Bernstein Wave (IBW) and Lower Hybrid Current Drive (LHCD) enhanced confinement plasma using a pneumatically driven Langmuir probe array on HT-7 tokamak. In the enhanced confinement plasma, the gradients of electron density and temperature become higher and a transport barrier comes into being in the vicinity of the limiter. The boundary potential shows a clear modification in the same region. The fluctuation levels are significantly depressed and the coherences between fluctuations are reduced evidently in the enhanced plasma. Meanwhile, we obtained the spectral features and the poloidal phase velocity of fluctuations using a two-point correlation technique and found obvious modifications of the turbulence and the poloidal flow. The results suggest that the improved confinement in the IBW and LHCD enhanced plasma is at least partially due to the modification of the boundary parameters and the suppression of the boundary fluctuations and fluctuation induced fluxes.

  9. Simulation Study on the ITB Formation during LHCD in JT-60U

    NASA Astrophysics Data System (ADS)

    Cui, Zheng-ying; Osamu, Naito; Takeshi, Fukudai; Hiroshi, Shirai; Yoshitaka, Ikeda; Kenkichi, Ushigusa

    2002-04-01

    A transport simulation has been done by using a 1.5D time dependent transport code to reproduce a formation of the ITB on electron temperature profile during the long pulse LHCD in JT-60U tokamak. The transport coefficients were assumed to reduce with a reversed magnetic shear and the LH driven current profile was evaluated by fitting dynamic change in the measured current profile. The gradual increase in the central electron temperature could be explained by the change in the current profile during LHCD in the present simulation model. The estimated LH-driven current profile by the transport code analysis shows a finite current density at the plasma center. Analysis of transport simulation suggests some mechanisms for broadening the LH-driven current profile at the central region of the plasma.

  10. Estimation of the current driven by residual loop voltage in LHCD plasma on EAST Tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, X. M.; Yu, L. M.; Wan, B. N.; Xue, E. B.; Fang, Y.; Shi, K. Y.; EAST Team

    2016-02-01

    The lower hybrid wave current drive (LHCD) is one of the efficient methods of driving the non-inductive current required for Tokamak operating in steady-state. Residual loop voltage exists in Tokamak when the non-inductive current is not fully driven. Residual loop voltage also accelerates the fast electrons generated by the lower hybrid wave (LHW), which can drive extra current and combine with the current driven by the LHW. It is generally difficult to separate these two different components of driven current in the experiment. In this paper, the currents driven by LHCD and residual loop voltage are separated directly by solving the Fokker-Plank equation numerically. The fraction of the current driven by residual loop voltage compared to the current driven by LHW is evaluated on the experimental advanced superconducting tokamak (EAST). The current driven by residual loop voltage is several percent of the currents driven by the LHCD when the residual loop voltage is small, but it increases with the residual loop voltage up to 25% when the residual loop voltage is about 2 V. The hot electrical conductivity is deduced from the net current driven by the residual loop voltage. Its distribution profile is related to the fast electron distribution driven by LHW.

  11. System calibration of the 1.4 GHz and 5 GHz radiometers for soil moisture remote sensing

    NASA Technical Reports Server (NTRS)

    Wang, J.; Shiue, J.; Gould, W.; Fuchs, J.; Hirschmann, E.; Glazar, W.

    1980-01-01

    Two microwave radiometers at the frequencies of 1.4 GHz and 5 GHz were mounted on a mobile tower and used for a remote sensing of soil moisture experiment at a Beltsville Agriculture Research Center test site. The experiment was performed in October 1979 over both bare field and fields covered with grass, soybean, and corn. The calibration procedure for the radiometer systems which forms the basis of obtaining the final radiometric data product is described. It is estimated from the calibration results that the accuracy of the 1.4 GHz radiometric measurements is about + or - 3 K. The measured 5 GHz brightness temperatures over bare fields with moisture content greater than 10 percent by dry weight are about 8 K lower than those taken simultaneously at 1.4 GHz. This could be due to either (1) a 5 GHz antenna side lobe seeing the cold brightness of the sky, or (2) the thermal microwave emission from a soil being less sensitive to surface roughness at 5 GHz than at 1.4 GHz.

  12. The ATLAS 5.5 GHz Survey of the Extended Chandra Deep Field South: Source Counts and Spectral Indices

    NASA Astrophysics Data System (ADS)

    Huynh, Minh T.; Hopkins, A. M.; Lenc, E.; Mao, M.; Middelberg, E.; Norris, R.; Randall, K.

    2013-01-01

    Star forming galaxies are thought to dominate the sub-mJy radio population, but recent work has shown that low luminosity AGN can still make a significant contribution to the faint radio source population. We have observed the extended Chandra Deep Field South at 5.5 GHz using a mosaic of 42 pointings with the Australia Telescope Compact Array (ATCA). Our image reaches an almost uniform sensitivity of ~12 μJy rms over 0.25 deg^2 with a restoring beam of 4.9 × 2.0 arcsec, making it one of the deepest 6cm surveys to date. We present the 5.5 GHz source counts from this field. We take advantage of the large amounts of ancillary data in this field to study the 1.4 to 5.5 GHz spectral indices of the sub-mJy population. For the full 5.5 GHz selected sample we find a flat median spectral index, α_med = -0.40, consistent with previous results. However, the spectral index appears to steepen at the faintest flux density levels (S5.5GHz < 0.1 mJy), where α_med = -0.68. We performed stacking analysis of the faint 1.4 GHz selected sample (40 < S1.4GHz < 200 microJy) and also find a steep average spectral index, α = -0.8, consistent with synchrotron emission. We find a weak trend of steepening spectral index with redshift. Several young AGN candidates are identified using spectral indices, suggesting gigahertz peaked spectrum (GPS) sources are as common in the mJy population as they are at Jy levels.

  13. 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.

  14. Enhancement of KSTAR plasma control for expanding operational space

    NASA Astrophysics Data System (ADS)

    Hahn, Sang-Hee; Jeon, Y. M.; Han, H.; Ahn, H. S.; Kim, J.; Kim, Y. J.; Joung, M.; Woo, M. H.; Mueller, D.; Eidietis, N. W.; Lanctot, M.; Humphreys, D. A.; Hyatt, A. W.; Welander, A. S.; Walker, M. L.; Kolemen, E.; Park, Y. S.; Sabbagh, S. A.

    2015-11-01

    In order to expand the operational space with stationary high performances, new approaches on the magnetic control design are necessary. A few examples on recent achievements at KSTAr are presented here: The Introduction of the in-vessel radial control (IRC) provides a fundamental change on baseline axisymmetric magnetic controls. Analysis on dedicated simulations/experiments for the vertical stabilization control margin gave an insight for improvement of the vertical position control. In order to enhance flexibility on the non-axisymmetric 3D field physics studies, the KSTAR RMP coil systems have been upgraded in 2015 provide more variety on the available 3D field profile. Integration of real-time heating device control enabled more elaborate kinetic controls since 2013. Real-time TM suppression is introduced as an example of the integrated control, which will be linked to stability control in the high-beta regime relevant to ITER success.

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

    SciTech Connect

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

    2016-11-15

    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 {sup 3}He 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.

  16. Initial measurements of fast ion loss in KSTAR

    SciTech Connect

    Kim, Junghee; Yoon, S. W.; Kim, W. C.; Kim, Jun Young; Garcia-Munoz, M.; Isobe, M.

    2012-10-15

    A fast ion loss detector (FILD) has been installed and tested in Korea Superconducting Tokamak Advanced Research (KSTAR). KSTAR FILD measures the energy and the pitch-angle of the escaping ions with the striking positions on the scintillator plane. Measurements of the fast ion loss have been performed for the neutral beam heated plasmas. Initial experimental results indicate the prompt losses from neutral beam are dominant and the effects of the resonant magnetic perturbation on the fast ion loss are investigated. In addition, further design change of the detector-head in order to avoid excessive heat load and to detect the fusion products or the fast ions having order of MeV of energy is also discussed.

  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. Imaging x-ray crystal spectrometers for KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, S. G.; Bak, J. G.; Bitter, M.; Moon, M. K.; Nam, U. W.; Jin, K. C.; Kong, K. N.; Seon, K. I.

    2003-03-01

    Two x-ray imaging crystal spectrometers are presently designed for the KSTAR tokamak. The instruments will provide temporally and spatially resolved spectra of heliumlike argon (or krypton) from a large cross section of the plasma. The spectral data will be used for profile measurements—both within and perpendicular to the horizontal midplane of KSTAR—of the ion and electron temperatures, the rotation velocity, and the ionization equilibrium. Each spectrometer will consist of a spherically bent quartz crystal and large area two-dimensional position-sensitive multiwire proportional counter. The article presents the design for the KSTAR x-ray imaging crystal spectrometers, and the fabrication and initial test results from the large area two-dimensional multiwire proportional counter.

  20. In-vessel visible inspection system on KSTAR.

    PubMed

    Chung, Jinil; Seo, D C

    2008-08-01

    To monitor the global formation of the initial plasma and damage to the internal structures of the vacuum vessel, an in-vessel visible inspection system has been installed and operated on the Korean superconducting tokamak advanced research (KSTAR) device. It consists of four inspection illuminators and two visible/H-alpha TV cameras. Each illuminator uses four 150 W metal-halide lamps with separate lamp controllers, and programmable progressive scan charge-coupled device cameras with 1004 x 1004 resolution at 48 framess and a resolution of 640 x 480 at 210 framess are used to capture images. In order to provide vessel inspection capability under any operation condition, the lamps and cameras are fully controlled from the main control room and protected by shutters from deposits during plasma operation. In this paper, we describe the design and operation results of the visible inspection system with the images of the KSTAR Ohmic discharges during the first plasma campaign.

  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. Progress in development of the KSTAR Thomson scattering system

    NASA Astrophysics Data System (ADS)

    Lee, Jongha; Oh, Seung Tae

    2010-05-01

    The design of Thomson scattering system for the Korean Superconducting Tokamak Advanced Research (KSTAR) device is described. The system includes a laser beam guiding system, laser input port, laser beam dump, collection lens, shutter, and cassette system. The laser guiding system has a collimating lens set for reducing the laser power loss. The laser beam dump will be attached inside of the vacuum vessel and hence it has been designed compactly. The preliminary design of collection lens, shutter system, and the cassette were done by PPPL and the engineering design is being executed by NFRI. The collection lens system has two sets of lenses, one set is designed for the core and the other set is designed for the edge. Two sets of pneumatic shutter systems are designed for independent remote control. Most of the KSTAR Thomson scattering system design is already finished and we are planning to install the whole system by March, 2010. We will measure the plasma parameters (Te, ne) in KSTAR during the third campaign.

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

    PubMed

    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.

  4. 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.

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

    SciTech Connect

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

    2014-11-15

    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.

  6. Shutdown Dose Rate Analysis for the long-pulse D-D Operation Phase in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Jin Hun; Han, Jung-Hoon; Kim, D. H.; Joo, K. S.; Hwang, Y. S.

    2017-09-01

    KSTAR is a medium size fully superconducting tokamak. The deuterium-deuterium (D-D) reaction in the KSTAR tokamak generates neutrons with a peak yield of 3.5x1016 per second through a pulse operation of 100 seconds. The effect of neutron generation from full D-D high power KSTAR operation mode to the machine, such as activation, shutdown dose rate, and nuclear heating, are estimated for an assurance of safety during operation, maintenance, and machine upgrade. The nuclear heating of the in-vessel components, and neutron activation of the surrounding materials have been investigated. The dose rates during operation and after shutdown of KSTAR have been calculated by a 3D CAD model of KSTAR with the Monte Carlo code MCNP5 (neutron flux and decay photon), the inventory code FISPACT (activation and decay photon) and the FENDL 2.1 nuclear data library.

  7. High-resolution maps of the 1.5 GHz emission from Jupiter's disk and radiation belt

    NASA Technical Reports Server (NTRS)

    Roberts, J. A.; Berge, G. L.; Bignell, R. C.

    1984-01-01

    VLA maps of four different faces of Jupiter made with a resolution of about 0.3 Jovian radius show new features of the radiation belt emission. A synchrotron model which reproduces these features serves to define the major characteristics of the relativistic electrons in the radiation belt. The observations provide the best determination to date of the atmospheric emission at 1.5 GHz and yield a disk brightness temperature of 425 + or - 100 K.

  8. 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

    ... and GSO FSS services in the 29.25-29.5 GHz Bands. 25.258 Section 25.258 Telecommunication FEDERAL....258 Sharing between NGSO MSS Feeder links Stations and GSO FSS services in the 29.25-29.5 GHz Bands. (a) Operators of NGSO MSS feeder link earth stations and GSO FSS earth stations in the band 29.25 to...

  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

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 25 Allocation and Designation of Spectrum for Fixed-Satellite Services in the 37.5-38.5 GHz, 40.5-41.5 GHz and 48.2-50.2 GHz Frequency Bands AGENCY: Federal Communications...

  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

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 25 Allocation and Designation of Spectrum for Fixed-Satellite Services in the 37.5-38.5 GHz, 40.5-41.5 GHz and 48.2-50.2 GHz Frequency Bands AGENCY: Federal Communications...

  11. 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.

  12. 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.

  13. Ramp generator circuit for probe diagnostics using microcontroller for LHCD system

    NASA Astrophysics Data System (ADS)

    Virani, C. G.; Sharma, P. K.; Lhcd Group

    2010-02-01

    It is well known that in LHCD system, the rf power coupling between antenna and plasma strongly depends on the edge plasma parameter. Thus it is mandatory to monitor edge plasma parameter to establish proper impedance matching condition when LHCD power is launched into the plasma. For SST1 LHCD system, we intend to monitor the edge plasma parameter employing electric probes, connected to the grill antenna sides for the said purpose. In SST1, initially LHCD system would couple rf power to plasmas lasting for small durations. Gradually the power and pulse length would be increased to eventually get 1000 seconds plasma. To monitor the edge plasma parameter, over such a wide spectrum (say few millisecond to seconds) during the above campaign, a flexible measurement scheme is desired which would cater to entire spectrum of operation. Normally a ramp is utilized to bias the electric probe, which yields various plasma parameters. To cater our requirement, the ramp generator must have facility to change ramp-up rate to meet our pulse length requirement. Further during SST operation, the human access near the machine would not be permitted and ramp circuit might not be accessible for manual settings. Thus remote setting facility to change ramp-up rate is also desired. Keeping these constraints in mind, a ramp circuit has been designed using Analog Device micro-controller ADuC842. The circuit has both manual and remote setting facility. Ramp generator parameters like Ramp-up rate, Trigger mode, number of cycles, etc. can be set from PC through RS-485 serial link. Initially low voltage (0-5V) ramp signal is generated using micro-controller and inbuilt DAC. This low voltage ramp is then amplified with PA-85 op-amp to get desired probe biasing voltage (-110V to +110V). The ramp period can be change form (1ms to 1000 ms) to cater to different plasma pulse length. Programming for micro-controller is done in structured language-C with the help of "Keil" IDE. In this paper, a

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

    SciTech Connect

    Mirizzi, F.

    2014-02-12

    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.

  15. 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.

  16. Relatively scaled ECE temperature profiles of KSTAR plasmas.

    PubMed

    Choi, M J; Yun, G S; Park, H K; Jeon, Y M; Jeong, S H

    2010-10-01

    A scheme to obtain relatively scaled profiles of electron cyclotron emission (ECE) temperature directly from uncalibrated raw radiometer data is proposed and has been tested for the 2009 campaign KSTAR plasmas. The proposed method utilizes a position controlled system to move the plasma adiabatically and compares ECE radiometer channels at the same relative radial positions assuming the profile consistency during the adiabatic change. This scaling method is an alternative solution when an absolute calibration is unreliable or too time consuming. The application to the two dimensional ECE imaging data, wherein calibration is extremely difficult, may also prove to be useful.

  17. Relatively scaled ECE temperature profiles of KSTAR plasmas

    SciTech Connect

    Choi, M. J.; Yun, G. S.; Park, H. K.; Jeon, Y. M.; Jeong, S. H.

    2010-10-15

    A scheme to obtain relatively scaled profiles of electron cyclotron emission (ECE) temperature directly from uncalibrated raw radiometer data is proposed and has been tested for the 2009 campaign KSTAR plasmas. The proposed method utilizes a position controlled system to move the plasma adiabatically and compares ECE radiometer channels at the same relative radial positions assuming the profile consistency during the adiabatic change. This scaling method is an alternative solution when an absolute calibration is unreliable or too time consuming. The application to the two dimensional ECE imaging data, wherein calibration is extremely difficult, may also prove to be useful.

  18. Development of 2 MW Dummy Load for KSTAR ICH System

    SciTech Connect

    Kwak, Jong-Gu; Wang, Son Jong; Bae, Young Dug; Yoon, Jae Sung; Hong, Bong Guen

    2005-09-26

    A 2 MW dummy load with a frequency ranging from 30 to 60 MHz is developed for the KSTAR ICH transmitter and the cold test shows that VSWR is less than 1.35 for the temperature variation of 17 deg. C. DC test also shows that overall temperature increase is less than 3 deg. C for 400 kW. RF test is done for the RF power of 140 kW and Max. VSWR is about 1.4 at the temperature of 40 deg. C.

  19. Rotational resonance of nonaxisymmetric magnetic braking in the KSTAR tokamak.

    PubMed

    Park, J-K; Jeon, Y M; Menard, J E; Ko, W H; Lee, S G; Bae, Y S; Joung, M; You, K-I; Lee, K-D; Logan, N; Kim, K; Ko, J S; Yoon, S W; Hahn, S H; Kim, J H; Kim, W C; Oh, Y-K; Kwak, J-G

    2013-08-30

    One of the important rotational resonances in nonaxisymmetric neoclassical transport has been experimentally validated in the KSTAR tokamak by applying highly nonresonant n=1 magnetic perturbations to rapidly rotating plasmas. These so-called bounce-harmonic resonances are expected to occur in the presence of magnetic braking perturbations when the toroidal rotation is fast enough to resonate with periodic parallel motions of trapped particles. The predicted and observed resonant peak along with the toroidal rotation implies that the toroidal rotation in tokamaks can be controlled naturally in favorable conditions to stability, using nonaxisymmetric magnetic perturbations.

  20. Commissioning activities of the initial magnetic diagnostics for KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Lee, Sang Gon; Gyo Bak, Jun; Mie Ka, Eun

    2007-11-01

    The initial magnetic diagnostics for the KSTAR superconducting tokamak including three Rogowski coils, five flux/voltage loops, and sixty-four magnetic field probes have been successfully installed. The Rogowski coils, flux/voltage loops, and magnetic field probes measure the total plasma current, poloidal flux and loop voltage, and local poloidal magnetic field for the plasma position control and equilibrium studies, respectively. Accurate position measurements after installation for all of these initial magnetic diagnostics and in situ calibration for the Rogowski coils were finished. Data acquisition systems for these initial magnetic diagnostics are currently under preparation. Detail commissioning activities before the first plasma from these initial magnetic diagnostics will be presented.

  1. Development of 2 MW Dummy Load for KSTAR ICH System

    NASA Astrophysics Data System (ADS)

    Kwak, Jong-Gu; Wang, Son Jong; Bae, Young Dug; Yoon, Jae Sung; Hong, Bong Guen

    2005-09-01

    A 2 MW dummy load with a frequency ranging from 30 to 60 MHz is developed for the KSTAR ICH transmitter and the cold test shows that VSWR is less than 1.35 for the temperature variation of 17 °C. DC test also shows that overall temperature increase is less than 3 °C for 400 kW. RF test is done for the RF power of 140 kW and Max. VSWR is about 1.4 at the temperature of 40 °C.

  2. 1.5 GHz picosecond pulse generation from a monolithic waveguide laser with a graphene-film saturable output coupler.

    PubMed

    Mary, Rose; Brown, Graeme; Beecher, Stephen J; Torrisi, Felice; Milana, Silvia; Popa, Daniel; Hasan, Tawfique; Sun, Zhipei; Lidorikis, Elefterios; Ohara, Seiki; Ferrari, Andrea C; Kar, Ajoy K

    2013-04-08

    We fabricate a saturable absorber mirror by coating a graphene- film on an output coupler mirror. This is then used to obtain Q-switched mode-locking from a diode-pumped linear cavity channel waveguide laser inscribed in Ytterbium-doped Bismuthate Glass. The laser produces 1.06 ps pulses at ~1039 nm, with a 1.5 GHz repetition rate, 48% slope efficiency and 202 mW average output power. This performance is due to the combination of the graphene saturable absorber and the high quality optical waveguides in the laser glass.

  3. 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).

  4. Prompt loss of beam ions in KSTAR plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Jun Young; Rhee, T.; Kim, Junghee; Yoon, S. W.; Park, B. H.; Isobe, M.; Ogawa, K.; Ko, W.-H.

    2016-10-01

    For a toroidal plasma facility to realize fusion energy, researching the transport of fast ions is important not only due to its close relation to the heating and current drive efficiencies but also to determine the heat load on the plasma-facing components. We present a theoretical analysis and orbit simulation for the origin of lost fast-ions during neutral beam injection (NBI) heating in Korea Superconducting Tokamak Advanced Research (KSTAR) device. We adopted a two-dimensional phase diagram of the toroidal momentum and magnetic moment and describe detectable momentums at the fast-ion loss detector (FILD) position as a quadratic line. This simple method was used to model birth ions deposited by NBI and drawn as points in the momentum phase space. A Lorentz orbit code was used to calculate the fast-ion orbits and present the prompt loss characteristics of the KSTAR NBI. The scrape-off layer deposition of fast ions produces a significant prompt loss, and the model and experimental results closely agreed on the pitch-angle range of the NBI prompt loss. Our approach can provide wall load information from the fast ion loss.

  5. Enhanced understanding of momentum transport barrier observed in KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, H. H.; Seol, J.; Ko, W. H.; Terzolo, L.; Aydemir, A. Y.; in, Y.; Ghime, Y. C.; Lee, S. G.

    2016-10-01

    It is expected that H-mode plasmas exhibit transport barriers not only for plasma particles and energy but also for toroidal angular momentum. Although density and temperature pedestals at the edge have been seen since the first observations of H-mode in tokamaks three decades ago, a toroidal rotation pedestal is not commonly observed except in some special cases such as QH-mode or is much weaker than those in the density and temperature profiles. But, in the KSTAR tokamak, H-mode plasma is always accompanied by the noticeable toroidal rotation pedestal. We show that the inherent nonaxisymmetric error fields and toroidal ripple can generate significant neoclassical toroidal viscosity (NTV), which damps the toroidal rotation at the edge and to a large extent remove the pedestal in the rotation profile. On the other hand, we demonstrate 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. Thus we conclusively show that H-mode provides a transport barrier against all three transport channels when turbulent transport is suppressed at the edge.

  6. Control and Data Acquisition System for KSTAR ICRF

    SciTech Connect

    Wang, S. J.; Kwak, J. G.

    2009-11-26

    An ICRF discharge cleaning and a plasma heating experiment were performed in KSTAR toka-mak. For an automated operation and the diagnostics of the ICRF system, the ICRF local network was designed and implemented. This internal network provides monitoring, RF protection, remote control and RF diagnostics. All the functions of the control system were realized by customized DSP units. The DSP units were tied by a local network in parallel. For RF diagnostics, a detector based on digital I/Q demodulation technique was fabricated. The I/Q detector collects the RF amplitude and phase at the same time without errors from I/Q imbalance inherent in an analog counterpart. During the first experimental campaign of the KSTAR tokamak, the control system was operated as expected without any major problems such as affecting the tokamak operation. The transmitter was protected from the harmful over-voltage events through a reliable operation of the system. Details of ICRF control system and RF detecting technique with a brief experimental result will be presented.

  7. In-vessel visible inspection system on KSTAR

    NASA Astrophysics Data System (ADS)

    Chung, Jinil; Seo, D. C.

    2008-08-01

    To monitor the global formation of the initial plasma and damage to the internal structures of the vacuum vessel, an in-vessel visible inspection system has been installed and operated on the Korean superconducting tokamak advanced research (KSTAR) device. It consists of four inspection illuminators and two visible/H-alpha TV cameras. Each illuminator uses four 150W metal-halide lamps with separate lamp controllers, and programmable progressive scan charge-coupled device cameras with 1004×1004 resolution at 48frames/s and a resolution of 640×480 at 210frames/s are used to capture images. In order to provide vessel inspection capability under any operation condition, the lamps and cameras are fully controlled from the main control room and protected by shutters from deposits during plasma operation. In this paper, we describe the design and operation results of the visible inspection system with the images of the KSTAR Ohmic discharges during the first plasma campaign.

  8. Installation of a fast framing visible camera on KSTAR.

    PubMed

    Chung, Jinil; Lee, Deok Kyo; Seo, Dongcheol; Choi, Myoung Choul

    2008-10-01

    Visible camera technologies have made remarkable progress in recent years, and the fast camera has proven itself to be a capable imaging diagnostic in studies of specific fusion plasma issues such as the start-up physics, plasma wall interactions, edge-localized modes, and disruptions. For the purpose of favorable visible imaging, a fast framing camera has recently been installed on the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1280x1024 at 1000 frames/s (fps) and a minimum resolution of 1280x16 at 64 kfps. A 2-m-long viewport having a novel optical rail system was installed on a tangential port to view the tokamak interior. The system is fully controlled from the main control room and protected by a shutter from deposits. To verify that the camera electronics are safe from the high magnetic field and its rapid time variation, possible influences are considered theoretically and experimentally. In this work, we present the design and installation of the fast camera system on the KSTAR device with discussions on the field variation effect issues.

  9. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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 ~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.

  11. 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.

  12. 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.

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

    SciTech Connect

    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.

    2011-12-23

    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.

  14. 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.

  15. 39.5-GHz static frequency divider implemented in AlInAs/GaInAs HBT technology

    NASA Astrophysics Data System (ADS)

    Hafizi, Madjid; Jensen, Joseph F.; Metzger, Robert A.; Stanchina, William E.; Rensch, David B.; Allen, Young K.

    1992-12-01

    A static divide-by-4 frequency divider operating at 39.5 GHz with a corresponding gate delay of 12.6 ps was implemented using InP-based HBT technology. The AlInAs/GaInAs HBT devices utilized in the divider incorporated a graded emitter-base (E-B) junction and had a unity gain cutoff frequency, maximum frequency of oscillation, and current gain of 130 GHz, 91 GHz, and 39, respectively. The divider was operated with a 3-V power supply and consumed a total power of 425 mW (77 mW per flip-flop). The divider functional yield was over 90 percent. The operating frequency of this circuit is the highest ever reported for a static divider.

  16. 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).

  17. The eMERGE Survey - I: Very Large Array 5.5 GHz observations of the GOODS-North Field

    NASA Astrophysics Data System (ADS)

    Guidetti, D.; Bondi, M.; Prandoni, I.; Muxlow, T. W. B.; Beswick, R.; Wrigley, N.; Smail, I.; McHardy, I.; Thomson, A. P.; Radcliffe, J.; Argo, M. K.

    2017-10-01

    We present new observations of the GOODS-N field obtained at 5.5 GHz with the Karl G. Jansky Very Large Array. The central region of the field was imaged to a median rms of 3 μJy beam-1 with a resolution of 0.5 arcsec. From a 14-arcmin diameter region, we extracted a sample of 94 radio sources with signal-to-noise ratio greater than 5. Near-IR identifications are available for about ∼88 per cent of the radio sources. We used different multiband diagnostics to separate active galactic nuclei (AGNs), both radiatively efficient and inefficient, from star-forming galaxies. From our analysis, we find that about 80 per cent of our radio-selected sample is AGN dominated, with the fraction rising to 92 per cent when considering only the radio sources with redshift >1.5. This large fraction of AGN-dominated radio sources at very low flux densities (the median flux density at 5.5 GHz is 42 μJy), where star-forming galaxies are expected to dominate, is somewhat surprising and at odds with other results. Our interpretation is that both the frequency and angular resolution of our radio observations strongly select against radio sources whose brightness distribution is diffuse on a scale of several kpc. Indeed, we find that the median angular sizes of the AGN-dominated sources is around 0.2-0.3 arcsec against 0.8 arcsec for star-forming galaxies. This highlights the key role that high frequency radio observations can play in pinpointing AGN-driven radio emission at μJy levels. This work is part of the eMERGE legacy project.

  18. New JVLA observations at 3 GHz and 5.5 GHz of the "Kite" radio source in Abell 2626

    NASA Astrophysics Data System (ADS)

    Ignesti, A.; Gitti, M.; Brunetti, G.; Feretti, L.; Giovannini, G.

    2017-07-01

    Context. We report on new Karl Jansky Very Large Array (JVLA) observations performed at 3 GHz and 5.5 GHz of Abell 2626. The cluster has been the object of several studies in recent years due to its peculiar radio emission, which shows a complex system of symmetric radio arcs characterized by a steep spectrum. The origin of these radio sources is still unclear. Due to their mirror symmetry toward the center, it has been proposed that they may be created by pairs of precessing jets powered by the inner active galactic nuclei (AGN). Aims: The new JVLA observations were requested with the specific aim of detecting extended emission on frequencies higher than 1.4 GHz, in order to constrain the jet-precession model by analyzing the spectral index and radiative age patterns along the arcs. Methods: We performed a standard data reduction of the JVLA datasets with the software CASA. By combining the new 3 GHz data with the archival 1.4 GHz VLA dataset we produced a spectral index map of the extended emission, and then estimated the radiative age of the arcs by assuming that the plasma was accelerated in moving hot-spots tracing the arcs. Results: Thanks to the high sensitivity of the JVLA, we achieve the detection of the arcs at 3 GHz and extended emission at 5.5 GHz. We measure a mean spectral index <- 2.5 for the arcs up to 3 GHz. No clear trend in spectral index or radiative age is detected across the arcs, which may challenge the interpretation based on precession or put strong constraints on the jet-precession period. In particular, by analyzing the radiative age distribution along the arcs, we were able to provide for the first time a timescale <26 Myr of the jet-precession period.

  19. First results of the resistive bolometers on KSTAR.

    PubMed

    Seo, Dongcheol; Peterson, B J; Lee, Seung Hun

    2010-10-01

    The resistive bolometers have been successfully installed in the midplane of L-port in Korea Superconducting Tokamak Advanced Research (KSTAR) device. The spatial and temporal resolutions, 4.5 cm and ∼1 kHz, respectively, enable us to measure the radial profile of the total radiated power from magnetically confined plasma at a high temperature through radiation and neutral particles. The radiated power was measured at all shots. Even at low plasma current, the bolometer signal was detectable. The electron cyclotron resonance heating (ECH) has been used in tokamak for ECH assisted start-up and plasma control by local heating and current drive. The detectors of resistive bolometer, near the antenna of ECH, are affected by electron cyclotron wave. The tomographic reconstruction, using the Phillips-Tikhonov regularization method, will be carried out for a major radial profile of the radiation emissivity of the circular cross-section plasma.

  20. First results of the resistive bolometers on KSTAR

    SciTech Connect

    Seo, Dongcheol; Peterson, B. J.; Lee, Seung Hun

    2010-10-15

    The resistive bolometers have been successfully installed in the midplane of L-port in Korea Superconducting Tokamak Advanced Research (KSTAR) device. The spatial and temporal resolutions, 4.5 cm and {approx}1 kHz, respectively, enable us to measure the radial profile of the total radiated power from magnetically confined plasma at a high temperature through radiation and neutral particles. The radiated power was measured at all shots. Even at low plasma current, the bolometer signal was detectable. The electron cyclotron resonance heating (ECH) has been used in tokamak for ECH assisted start-up and plasma control by local heating and current drive. The detectors of resistive bolometer, near the antenna of ECH, are affected by electron cyclotron wave. The tomographic reconstruction, using the Phillips-Tikhonov regularization method, will be carried out for a major radial profile of the radiation emissivity of the circular cross-section plasma.

  1. Development of X-ray Imaging Crystal Spectrometer for KSTAR

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

    The engineering design for two high-resolution X-ray imaging crystal spectrometers, which will be part of the basic diagnostics for the KSTAR tokamak, has been finalized. Each of the spectrometers will consists of a spherically bent crystal and a 10 cm x 30 cm large 2D position-sensitive multi-wire proportional counter. The instruments will provide spatially and temporally resolved spectra of the resonance line of helium-like argon (or krypton) and the associated satellites from multiple lines of sight parallel and perpendicular to the horizontal mid-plane for measurements of the profiles of the ion and electron temperatures, plasma rotation velocity, and ionization equilibrium. A 2D detector with delay-line readout and supporting electronics has been fabricated and calibrated with an X-ray source. The engineering design of the spectrometers and the calibration results of the 2D detector will be presented.

  2. Ray Tracing Study of 170GHZ Electron Cyclotron Waves in Kstar Plasmas

    NASA Astrophysics Data System (ADS)

    Bae, Young-Soon; Joung, M.; Yang, H. L.; Namkung, W.; Cho, M. H.; Park, H.; Prater, R.; Ellis, R. A.; Hosea, J.

    2011-02-01

    The electron cyclotron heating/current drive (ECH/ECCD) system has become an essential tool for the fusion plasma research in toroidal devices. In Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak, development of high power and multi-frequency ECH/ECCD system is in progress. The frequencies employed in KSTAR are 84 GHz, 110 GHz, and 170 GHz. Multiple frequency sources can easily support the wide range of operating regimes from 1.5 T to 3.5 T in KSTAR tokamak. In particular, the 170 GHz source, that will be adapted to the ITER, corresponds to the second harmonic frequency of the KSTAR operating range from 2.6 T to 3.5 T. This frequency will be mainly used for the control of the local plasma current profile to manipulate the internal MHD instabilities such as the neoclassical tearing mode (NTM) critical in high-beta plasma operation. This paper presents simulated ray tracings of the 170 GHz EC waves for a various plasma conditions in KSTAR. The TORAY-GA ray tracing code is used, along with Interactive Data Language (IDL) procedures that create the input files, to study the effect of ECH/ECCD on the plasma equilibrium profiles as a function of the initial density and temperature profiles and of toroidal field.

  3. Investigation of MHD instabilities and their dependence on plasma rotation in KSTAR*

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Berkery, J. W.; Bialek, J. M.; Jeon, Y. M.; Hahn, S. H.; Kim, J.; You, K.-I.; Lee, S. G.; Bak, J. G.; Lee, K. D.; Ko, W. H.; Bae, Y. S.

    2011-10-01

    A goal of the Korea Superconducting Tokamak Advanced Research (KSTAR) is to perform physics studies in support of ITER. With co-directed neutral beam injection, one expected difference between KSTAR and ITER is the degree and profile of the plasma rotation, which affects plasma stability. The present work examines instabilities that exist in KSTAR under plasma rotation conditions spanning the entire KSTAR operational space. Mode characteristics measured by electron cyclotron emission are compared to values computed from reconstructed plasma equilibria. Frequencies of the modes tied to plasma rotation are compared to measurements from an X-ray crystal spectrometer and charge exchange recombination spectroscopy. A first experiment producing non-resonant alteration of the plasma rotation profile by neoclassical toroidal viscosity will be attempted to access a low rotation operating space most applicable to ITER and examine the dependence of beta-limiting instabilities on rotation and rotation shear. Proximity of this new operational regime to MHD stability limits will be examined, as well as implications for n = 1 feedback stabilization planned for future KSTAR operation. Work supported by U.S. DOE grant DE-FG02-99ER54524.

  4. Simulation Study of Disruption and Halo Currents in the KSTAR Model Structure

    NASA Astrophysics Data System (ADS)

    Kim, J. Y.

    1999-11-01

    A detailed simulation study has been performed for the disruption load analysis in the Korea Superconducting Tokamak Advanced Research (KSTAR) device using the Tokamak Simulation Code. Two different types of disruptions (radial and vertical) are simulated for various initial equilibria and halo region models. Special emphasis is put on the behavior of halo currents in the KSTAR model structure, in which a highly conductive passive plate is located near the plasma. It is found that the path and magnitude of the poloidal halo current depend quite sensitively on the detailed structure model of the KSTAR plasma facing component (PFC). In particular, a local circulation of a very large poloidal halo current is observed to occur near the connector of the up-down passive plates when it is not electrically insulated. An explanation is presented for the physical origin of this rather unusual feature of the halo current in the KSTAR PFC environment. The large poloidal halo current can give a severe electromagnetic load to the KSTAR PFC structure, and an optimized PFC model structure is proposed which can substantially reduce the undesirable halo current.

  5. 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.

  6. 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

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

    PubMed

    Sasaki, K; Wake, K; Watanabe, S

    2014-08-21

    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.

  8. A 2 to 5GHz-Band Self Frequency Dividing Quadrature Mixer Using Current Re-Use Configuration

    NASA Astrophysics Data System (ADS)

    Taniguchi, Eiji; Shimozawa, Mitsuhiro; Suematsu, Noriharu

    A 2 to 5GHz-band self frequency dividing quadrature mixer utilizing current re-use configuration with small size and broad band operation is proposed for a direct conversion receiver and a low-IF receiver of cognitive radio. The proposed mixer operates at twice the LO frequency by directly using a static type flip-flop frequency divider as the LO switching circuit for quadrature signal generation. The current re-use configuration is realized because the dc current of the frequency divider and the RF common-emitter amplifier share the same current flow path. Simulations and experiments verify that the proposed mixer offers broad band operation, miniaturization, and low power consumption. The mixer IC fabricated by 0.35μm SiGe-BiCMOS technology achieved the conversion gain of 20.6dB, noise figure of 11.9dB and EVM for π/4-shift QPSK signal of 4.4% at 2.1GHz with power consumption of 15mW and size of 0.22×0.31mm2. For the confirmation of broad band operation, the characteristics of conversion gain and noise figure were measured at 5.2GHz. The proposed mixer could operate at 5.2GHz with enough conversion gain, but the noise figure was inferior to that of 2.1GHz. Therefore the further investigation and improvement about the noise figure will be needed for higher frequency.

  9. 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.

  10. 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).

  11. 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

  12. 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}.

  13. 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.

  14. 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.

  15. Development of the 3.7 GHz LHCD system on HL-2A

    NASA Astrophysics Data System (ADS)

    Lu, B.; Huang, M.; Zeng, H.; Bai, X. Y.; Mao, X. H.; Lu, Z. H.; Liang, J.; Kang, Z. H.; Wang, M. W.; Feng, K.; Wang, H.; Wang, C.; Wang, J. Q.; Wei, S.; Yao, T.; Bu, Y. N.; Feng, J.; Cheng, G. Y.; Song, S. D.; Xia, D. H.; Rao, J.

    2014-10-01

    A 2 MW-3.7 GHz lower hybrid current drive (LHCD) system is under development for physics experiments on the HL-2A device. The RF Power is generated by four TH2103A klystron amplifiers and propagates in the TE10 mode through WR284 waveguides. The transmission lines with a length of 20 m to 30 m are pressurized with 2 bars of nitrogen to decrease the possibility of arcing. The launcher, based on the passive-active multi-junction (PAM) concept, has been developed and is currently being realized. It was designed for a power spectrum peaked at N|| = 2.75 with good coupling properties over a wide range of plasma parameters. The four klystrons are fed by a high-voltage power supply (HVPS) based on the pulse step modulation (PSM) concept with a fast switch-off time of less than ten μs. This system is expected to be in operation within 1 years and will explore many international thermonuclear experimental reactor (ITER) related LH experiments in the following years.

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

    PubMed

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

    2014-11-01

    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.

  17. 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.

  18. Particle balance study for the fueling efficiency in KSTAR experiments 2013

    NASA Astrophysics Data System (ADS)

    Juhn, J.-. W.; Hahn, S. H.; Hong, S. H.; Song, J. I.; Kim, Y. O.; Kim, K. P.; Kim, J. S.

    2014-10-01

    The efficiencies of the fueling system in the KSTAR have been studied for the 2013 experimental results. The absolute amount of injected fuel or deuterium has been calibrated in advance of the main plasma experiments. This includes the primary actuator of fueling, i.e., gas puffing (GP) with piezoelectric valves located on mid-plane, and supersonic molecular beam injector (SMBI). In addition, neutral beam injectors (NBIs) and their base facility chamber also contribute to the amount of fuel injection whenever they are operated. Low fueling efficiency combined with particle loss due to wall retention essentially results in poor performance of density feedback control magnetic fusion devices such as the KSTAR.

  19. 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.

  20. 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.

  1. Simulation for heat flux mitigation by gas puffing in KSTAR

    NASA Astrophysics Data System (ADS)

    Shim, Seung Bo; Kotov, Vladislav; Hong, Suk-Ho; Detlev, Reiter; Kim, Jin Yong; Na, Yong Su; Lee, Hae June

    2013-10-01

    Control of heat flux is very important to achieve high performance long pulse operation in tokamaks. There are so many efforts to reduce the heat flux like change of divertor structure, snowflake divertor, and RMP, etc. Detachment by gas puffing is used for long time to reduce the heat flux. In this paper edge plasma scenarios of KSTAR are analyzed numerically by well-known B2-Eirene code package(SOLPS4.3). High performance discharges with heating power ~ 8 MW and core flux ~ 1021 s-1 is used. Gas puffed on the outer mid-plane(OMP), both divertors is likely to stay attached. So, gas puffed on the outer target, one is near the private flux region(PFR) and the other is near the scrape-off-layer(SOL). When gas puffed near the SOL is still attached, and it is worse than gas puff from OMP because it is too close to cryo-pump. The case near the PFR shows high recycling region easily compared with OMP case. When one forth gas puffed on the PFR, results are similar with OMP case. But it is still not good for detachment operation. Detachment operation window is too small for the gas puffing on the PFR. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MEST)(No. 2012-0000579).

  2. Improvement of X-ray Imaging Crystal Spectrometers for KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, Sang Gon; Bitter, M.; Nam, U. W.; Moon, M. K.

    2005-10-01

    The X-ray imaging crystal spectrometers for the KSTAR tokamak will provide spatially and temporally resolved spectra of the resonance line of helium-like argon (or krypton) and the associated satellites from multiple lines of sight parallel and perpendicular to the horizontal mid-plane for measurements of the profiles of the ion and electron temperatures, plasma rotation velocity, and ionization equilibrium. The spectrometers are consisted of a spherically bent quartz crystal and a 10 cm x 30 cm large 2D position-sensitive multi-wire proportional counter. A 2D detector with delay-line readout and supporting electronics has been fabricated and tested on the NSTX tokamak at PPPL. Position resolution and count rate capability of the 2D detector are still need to be improved to meet the requirements. Hence, a segmented version of the 2D detector is under development to satisfy the requirements. The experimental results from the improved 2D detector will be presented.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  5. 12.5-GHz-spaced laser frequency comb covering Y, J, and H bands for infrared Doppler instrument

    NASA Astrophysics Data System (ADS)

    Kokubo, T.; Mori, T.; Kurokawa, T.; Kashiwagi, K.; Tanaka, Y.; Kotani, T.; Nishikawa, J.; Tamura, M.

    2016-07-01

    In order to detect Earth-like planets around nearby red dwarfs (in particular late-M stars), it is crucial to conduct precise radial velocity measurements at near-infrared wavelengths where these stars emit most of the light. We have been developing the Infrared Doppler (IRD) spectrograph which is a high dispersion spectrograph for the Subaru telescope. To achieve 1m/s RV measurement precision, we have developed a direct generation of laser frequency comb (LFC) that uses high-repetition-rate pump pulse synthesized by a line-by-line pulse-shaping technique. Our LFC generator has some advantages including simple and easy frequency stabilization, all fiber-optic configuration, and broadband calibration by the precise frequency shift of all modes in the LFC. We have successfully generated a 12.5-GHz-spaced comb spanning over 700 nm from 1040 to 1750 nm. The frequency stability was measured by optically heterodyning the comb with an acetylene-stabilized laser at 1542 nm as a reference light. The LFC showed a frequency stability of less than 0.2 MHz and an almost constant spectrum profile for 6 days. The original LFC that has just produced from highly nonlinear fibers needs some optical processing including spectrum shaping, depolarization, and a mode scramble in a multi-mode fiber before it is input into a spectrograph for the calibration. We have investigated the optical processing of the LFC which is necessary for the precise spectrograph calibration. Keywords: laser frequency comb, infrared, spectrograph, Doppler shift

  6. 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).

  7. Development of advanced x-ray imaging crystal spectrometer utilizing a large area segmented proportional counter for KSTAR

    SciTech Connect

    Lee, S. G.; Bak, J. G.; Nam, U. W.; Moon, M. K.; Cheon, J. K.

    2007-06-15

    An advanced x-ray imaging crystal spectrometer (XICS) for KSTAR tokamak has been developed by utilizing a segmented two dimensional (2D) position-sensitive multiwire proportional counter. The XICS for the KSTAR tokamak provides time-resolved measurements of the radial ion and electron temperature profiles, toroidal plasma rotation velocity, and ionization equilibrium. The segmented 2D detector with delay-line readout and supporting electronics has been adopted to improve the photon count rate capability. The current fabrication status of the XICS for the KSTAR tokamak and the first performance test results of the prototype segmented 2D detector are presented.

  8. Development of advanced x-ray imaging crystal spectrometer utilizing a large area segmented proportional counter for KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, S. G.; Bak, J. G.; Nam, U. W.; Moon, M. K.; Cheon, J. K.

    2007-06-01

    An advanced x-ray imaging crystal spectrometer (XICS) for KSTAR tokamak has been developed by utilizing a segmented two dimensional (2D) position-sensitive multiwire proportional counter. The XICS for the KSTAR tokamak provides time-resolved measurements of the radial ion and electron temperature profiles, toroidal plasma rotation velocity, and ionization equilibrium. The segmented 2D detector with delay-line readout and supporting electronics has been adopted to improve the photon count rate capability. The current fabrication status of the XICS for the KSTAR tokamak and the first performance test results of the prototype segmented 2D detector are presented.

  9. Development of advanced x-ray imaging crystal spectrometer utilizing a large area segmented proportional counter for KSTAR.

    PubMed

    Lee, S G; Bak, J G; Nam, U W; Moon, M K; Cheon, J K

    2007-06-01

    An advanced x-ray imaging crystal spectrometer (XICS) for KSTAR tokamak has been developed by utilizing a segmented two dimensional (2D) position-sensitive multiwire proportional counter. The XICS for the KSTAR tokamak provides time-resolved measurements of the radial ion and electron temperature profiles, toroidal plasma rotation velocity, and ionization equilibrium. The segmented 2D detector with delay-line readout and supporting electronics has been adopted to improve the photon count rate capability. The current fabrication status of the XICS for the KSTAR tokamak and the first performance test results of the prototype segmented 2D detector are presented.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Design of an X-mode swept frequency modulation reflectometer for the measurement of KSTAR plasma density profiles (invited)

    NASA Astrophysics Data System (ADS)

    Roh, Y.; Domier, C. W.; Luhmann, N. C.

    2004-10-01

    An X-mode swept frequency modulation (FM) reflectometry system has been designed to measure the electron density profiles of the "initial" KSTAR plasma. Fast swept HTO oscillators are employed to avoid density fluctuation effects, and frequency quadruplers are utilized to expand the HTO frequency range of 8-18 GHz to completely cover the X-mode cutoff frequency range of 33-66 GHz. The system can also be utilized to measure the edge profiles of the "Day One" KSTAR plasma by either switching from X- to O-mode reflectometry or by employing higher frequency millimeter-wave components and retaining the X-mode reflectometry configuration. To facilitate engineering design and optimization, a 3D drawing tool is utilized to effectively deal with any technical problems that may happen under actual KSTAR conditions. Details of the KSTAR FM reflectometry system are described together with important design issues.

  15. 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.

  16. Test results of 3.7 GHz 500kW CW klystron for SST1 LHCD system

    NASA Astrophysics Data System (ADS)

    Sharma, Promod Kumar; Ambulkar, Kiran K.; Dalakoti, Shefali; Rajan Babu, N.; Parmar, Pramod R.; Virani, Chetan G.; Thakur, Arvind L.

    2012-10-01

    A 3.7 GHz, LHCD system aims to driving non inductive plasma current for SST1 machine. Its capability has been enhanced up to 2 MW by adding two additional klystrons, each rated for 500kW, CW power. The additional klystrons are installed and commissioned at site, for rated power, for more than 1000 seconds, before connecting them to main LHCD system. The auxiliary systems, like supporting power supply system (magnet, filament, ion pump, etc.), active heat management system, slow and fast interlock system, transmission line pressurization system, low power rf drive system, etc. are inter-connected with klystron system through VME based data acquisition and control system for remote CW operation of klystron at rated power. The calorimetric measurements, employing Pt-100 sensors, suggests that the maximum rf power (˜500kW CW) extracted from klystron is dissipated on water cooled dummy loads. The unspent DC power (˜800 kW CW) is dissipated in collector which is heavily cooled with water flowing at ˜1300 litres/min (lpm). The power loss in the klystron body remained within 20 kW. The cavity temperature, measured using J-type thermocouple, remained below 150 ^oC. The output rf power, sampled through directional couplers and measured by rf detectors shows good agreement with calorimetric measurements. A detailed description of the klystron test set up and the test results obtained during its commissioning is presented in this paper.

  17. 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.

  18. NOTE: Computational dosimetry in embryos exposed to electromagnetic plane waves over the frequency range of 10 MHz-1.5 GHz

    NASA Astrophysics Data System (ADS)

    Kawai, Hiroki; Nagaoka, Tomoaki; Watanabe, Soichi; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi

    2010-01-01

    This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in height and weight, with a cubic (4 week) embryo or spheroidal (8 week) one. The averaged SAR in the embryos exposed to vertically and horizontally polarized plane waves at four kinds of propagation directions are calculated from 10 MHz to 1.5 GHz. The results indicate that the maximum average SAR in the embryos exposed to plane waves is lower than 0.08 W kg-1 when the incident power density is at the reference level of ICNIRP guideline for general public environment.

  19. Extended MHD modeling of edge-localized mode suppression by three-dimensional magnetic perturbations in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, G. Y.; Kim, J.; Evans, T. E.; Lyons, B. C.; Orlov, D. M.; Ferraro, N. M.; in, Y.; Choi, M. J.; Yoon, S. W.

    2016-10-01

    In this presentation, we report on numerical calculations of the linear response of a plasma to applied three-dimensional magnetic perturbations (MPs) in KSTAR. Simulations are implemented using the extended MHD code M3D-C1. Initial M3D-C1 calculation of the plasma response in KSTAR has already produced results that are qualitatively consistent with some experimental characteristics observed during the application of MPs in KSTAR, i.e., amplified kink response and associated plasma displacements. Both of the tearing and kink responses are considered and used to explain the basic experimental characteristics of the suppression of edge-localized modes (ELMs) in KSTAR, i.e., q95, heating, and plasma shape dependences of the suppression. In particular, attention is focused on validation studies comparing the M3D-C1 plasma response results to the magnetic and imaging diagnostic measurements (i.e., ECEI data) in KSTAR. In addition, comparison study of the M3D-C1 results with KSTAR and DIII-D data will be presented to help understand a common ELM suppression mechanism which is expected to hold across the different tokamaks.

  20. 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....250 Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. (a) NGSO MSS applicants shall be licensed to operate in the 29.1-29.5 GHz band for...

  1. 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....250 Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. (a) NGSO MSS applicants shall be licensed to operate in the 29.1-29.5 GHz band for...

  2. 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....250 Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. (a) NGSO MSS applicants shall be licensed to operate in the 29.1-29.5 GHz band for...

  3. 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....250 Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. (a) NGSO MSS applicants shall be licensed to operate in the 29.1-29.5 GHz band for...

  4. 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....250 Sharing between NGSO MSS Feeder links Earth Stations in the 19.3-19.7 GHz and 29.1-29.5 GHz Bands. (a) NGSO MSS applicants shall be licensed to operate in the 29.1-29.5 GHz band for...

  5. Device and circuit modeling for a 3.5- to 6.5-GHz GaAs monolithic dual-gate FET switch module

    NASA Astrophysics Data System (ADS)

    Fu, Michael C.; Gupta, Ramesh K.

    The design approach and measured performance of a broadband (3.5- to 6.5-GHz), dual-gate field-effect transistor (DGFET) switch module with an on-chip, TTL-compatible switch control circuit are presented. This MMIC switch module is a key element in the development of a highly reliable and lightweight microwave switch matrix. A computer program was developed for modeling the equivalent circuit element values for the DGFET from physical device parameters. The program is used to predict the small-signal, three-port, S-parameters for DGFET devices. These modeled parameters are then used to design a self-biased monolithic DGFET switch module with chip dimensions of 1.5 x 2.5 mm. Measurements show that the switch module has an ON-state gain of approximately 11 dB over the 3.5- to 6.5-GHz range, with better than 50-dB ON- to-OFF isolation. The measured gain in the ON state is within 1 dB of the modeled performance over the 3.5- to 6.5-GHz band.

  6. 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.

  7. Comparative study between the reflective optics and lens based system for microwave imaging system on KSTAR

    SciTech Connect

    Lee, W.; Yun, G. S.; Nam, Y.; Hong, I.; Kim, J. B.; Park, H. K.; Tobias, B.; Liang, T.; Domier, C. W.; Luhmann, N. C. Jr.

    2010-10-15

    Recently, two-dimensional microwave imaging diagnostics such as the electron cyclotron emission imaging (ECEI) system and microwave imaging reflectometry (MIR) have been developed to study magnetohydrodynamics instabilities and turbulence in magnetically confined plasmas. These imaging systems utilize large optics to collect passive emission or reflected radiation. The design of this optics can be classified into two different types: reflective or refractive optical systems. For instance, an ECEI/MIR system on the TEXTOR tokamak [Park et al., Rev. Sci. Instrum. 75, 3787 (2004)] employed the reflective optics which consisted of two large mirrors, while the TEXTOR ECEI upgrade [B. Tobias et al., Rev. Sci. Instrum. 80, 093502 (2009)] and systems on DIII-D, ASDEX-U, and KSTAR adopted refractive systems. Each system has advantages and disadvantages in the standing wave problem and optical aberrations. In this paper, a comparative study between the two optical systems has been performed in order to design a MIR system for KSTAR.

  8. 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.

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

    PubMed

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

    2014-11-01

    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 (B0 = 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.

  10. Study on Sawtooth and ELM activities in DIII-D and KSTAR Plasmas

    NASA Astrophysics Data System (ADS)

    Bak, J.-G.; Kim, H. S.; Lee, S. G.; Lee, K. D.; Ko, W. H.; Kim, J.; Jeon, Y. M.; Kim, W. C.; Bae, Y. S.; Strait, E. J.; La Haye, R. J.; Buttery, R. J.; Wade, M. R.; Park, J. K.; Hanson, J. M.

    2012-10-01

    Sawtooth precursor oscillations (SPOs) are studied in neutral beam heated plasmas on DIII-D and KSTAR. The characteristics of the SPO (5-20 kHz, m/n=1/1) are investigated using magnetic sensors along with electron cyclotron emission (ECE) and soft x-ray diagnostics. In addition, the Type I edge localized mode (ELM) precursors (8-40 kHz, n=2,3) are detected before the ELM burst in neutral beam heated plasmas. The characteristics of the ELM precursors are investigated by using magnetic sensor data. In this work, the experimental investigations of the SPOs and ELM precursors in DIII-D and KSTAR plasmas will be presented.

  11. 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.

  12. 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.

  13. KSTAR first plasma equilibrium reconstruction and study of global MHD stability control

    NASA Astrophysics Data System (ADS)

    Katsuro-Hopkins, O.; Sabbagh, S. A.; Bialek, J. M.; Park, H. K.; You, K. I.; Lee, S. G.; Bak, J. G.; Yoon, S. W.; Kim, J. H.; Kim, J. Y.; Glasser, A. H.; Lao, L. L.

    2008-11-01

    Korea Superconducting Tokamak Advanced Research, KSTAR, equilibria are computed using EFIT and VALEN based on numerical models and recent experimental data from first plasma operation. A 3-D double-walled vacuum vessel model with port penetrations was used to evaluate the vacuum vessel effective resistance and to simulate and compare to the time evolution of experimental magnetic diagnostic measurements during vacuum poloidal field coil testing and plasma start-up scenarios. KSTAR is designed to produce wall-stabilized high beta equilibria. Ideal MHD stability of toroidal mode number of unity using DCON shows a factor of two improvement in the normalized beta limit over the no-wall beta limit (up to 5) at moderate to low plasma internal inductance. Reaching these high normalized beta levels is possible using passive and active control with classical and advanced state-space based control algorithms at the reasonable power levels.

  14. Critical aspects of ELM crash suppression by magnetic perturbations in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, Jayhyun; Jeon, Y. M.; Park, G. Y.; Choi, M. J.; in, Y.; Yoon, S. W.; Bae, C.; Lee, J.; Park, J.-K.; Ahn, J.; The Kstar Team Team

    2016-10-01

    ELM crash suppressions have been achieved by low n (n = 1, 2, and mixture of them) magnetic perturbations (MPs) with using various configurations of in-vessel perturbation coils in KSTAR. So far, the suppressed periods are extended longer than 10 seconds. In KSTAR, the complete suppression of ELM crashes almost always accompany with the increase of edge fluctuations which are likely to be excited by applied MPs. The excitation of edge fluctuation exhibited the bifurcation-like feature depending on the strength of MPs. The conditions to excite edge fluctuations were investigated with including well known q95 window. On the other hand, ELM mitigation does not come with the increase of edge fluctuations. Instead, it seems that applied MPs directly trigger small frequent ELMs since the mitigated ELMs suddenly disappear when turning MPs off. The results stress the importance of stability analysis with the use of perturbed equilibrium since most stability studies have assumed unperturbed/undistorted equilibrium.

  15. Current research activities and installation status of the X-ray imaging crystal spectrometer for KSTAR

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    An X-ray imaging crystal spectrometer (XICS) for KSTAR utilizing a four-segmented position-sensitive two dimensional (2D) multi-wire proportional counter and time-to-digital converter (TDC) based delay-line readout data acquisition system has been fabricated. The XICS provides spatially and temporally resolved measurements of the ion and electron temperatures, toroidal rotation velocity, impurity charge-state distributions, and ionization equilibrium. The four-segmented 2D detector with supporting electronics successfully demonstrated to improve the photon count-rate capability of the XICS system and a position resolution of the detector showed about 0.35 mm. A spectral resolution of the fabricated spectrometer has been measured using an X-ray tube before installation in the KSTAR tokamak. The current research activities and installation status of the spectrometer will be presented.

  16. Measurements and Modeling of X-Ray and ECE Spectra During LHCD Experiments on Alcator C-Mod

    SciTech Connect

    Schmidt, A. E.; Bonoli, P. T.; Hubbard, A. E.; Liptac, J.; Parker, R. R.; Wallace, G. M.; Wilson, J. R.; Harvey, R. W.; Smirnov, A. P.

    2007-09-28

    Lower Hybrid Current Drive (LHCD) has been demonstrated on Alcator C-Mod. The LH-driven fast electrons can be detected through hard x-ray Bremsstrahlung emission as well as relativistically downshifted electron cyclotron emission (ECE). C-Mod has a hard x-ray camera with 32 chords, as well as several outboard midplane ECE diagnostics. CQL3D/GENRAY is a modeling package that employs a 3-D Fokker-Planck solver to compute steady-state distribution functions for a given LH N{sub parallel} spectrum and plasma. It also can perform self-consistent synthetic diagnostic calculations. LH phase and power scans have been carried out. Fast electron diffusion time can be inferred from x-ray data. Experimental measurements are compared with synthetic diagnostic modeling to see how changes in phasing and power affect current profile control and to benchmark CQL3D in ITER-relevant regimes.

  17. 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.

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

    DOE PAGES

    Jeong, J. H.; Bae, Y. S.; Joung, M.; ...

    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

  19. Results of Beam Extraction Performance for the KSTAR Neutral Beam Injector

    NASA Astrophysics Data System (ADS)

    Chang, Doo-Hee; Jeong, Seung Ho; Kim, Tae-Seong; Lee, Kwang Won; Ryul In, Sang; Jin, Jung-Tae; Chang, Dae-Sik; Oh, Byung-Hoon; Bae, Young-Soon; Kim, Jong-Su; Cho, Wook; Park, Hyun-Taek; Park, Young-Min; Yang, Hyung-Lyeol; Watanabe, Kazuhiro; Dairaku, Masayuki; Tobari, Hiroyuki; Kashiwagi, Mieko; Hanada, Masaya; Inoue, Takashi

    2011-06-01

    The first neutral beam injector (NBI-1) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. The first long pulse ion source (LPIS-1) has been installed on the NBI-1 for an auxiliary heating and current drive of KSTAR plasmas. The performance of ion and neutral beam extractions in the LPIS-1 was investigated initially on the KSTAR NBI-1 system, prior to the neutral beam injection into the main plasmas. The ion source consists of a magnetic bucket plasma generator with multipole cusp fields and a set of prototype tetrode accelerators with circular apertures. The inner volume of the plasma generator and accelerator column in the LPIS-1 is approximately 123 L. Design requirements for the ion source were a 120 kV/65 A deuterium beam and a 300 s pulse length. The extraction of ion beams was initiated by the formation of arc plasmas in the LPIS-1, called the arc-beam extraction method. A stable ion beam extraction of the LPIS-1 was achieved up to 85 kV/32 A for a 5 s pulse length and 80 kV/25 A for a 14 s pulse length. An optimum beam perveance of 1.15 µperv was observed at an acceleration voltage of 60 kV. Neutralization efficiency was measured by a water-flow calorimetry (WFC) method using a calorimeter and the operation of a bending magnet. The full-energy species of ion beams were detected by using the diagnostic method of optical multichannel analyzer (OMA). An arc efficiency of the LPIS was 0.6-1.1 A/kW depending on the operating conditions of arc discharge. A neutral beam power of ˜1.0 MW must be sufficiently injected into the KSTAR plasmas from the LPIS-1 at a beam energy of 80 keV.

  20. 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.

  1. L-H power threshold studies under non-axisymmetric magnetic field in KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, Won-Ha; in, Y.; Kim, H. S.; Lee, H. H.; Lee, J. H.; Jeon, Y. M.; Seol, J.; Ida, K.; Yoon, S. W.; Oh, Y. K.; Park, H.

    2016-10-01

    An exceptionally low level of H-mode power threshold (PTH) , as well as its dependence on non-axisymmetric magnetic field (δB), has been measured in KSTAR. While the application of resonant magnetic perturbation (RMP) is deemed necessary to suppress or mitigate edge-localized-mode (ELM) in ITER and future reactors, δB influence on PTH in deuterium plasmas has been predicted to be mostly insensitive at low level, while linearly proportional at high level. However, in similarly neutral-beam-heated deuterium plasmas, we have found that the PTH of KSTAR was almost a factor of 2 lower than that of DIII-D, while revealing linear δB dependence even at its low level. Despite various differences between two devices in terms of RMP characteristics and configurations, such contrasting results are mostly attributable to an order of magnitude lower level of intrinsic error field and toroidal field ripple in KSTAR. Perhaps, a theory about L-H transition physics might be in better agreement with experimental results, when δB dependence is explicitly incorporated. National Fusion Research Institute.

  2. Numerical Study of Equilibrium, Stability, and Advanced Resistive Wall Mode Feedback Algorithms on KSTAR

    NASA Astrophysics Data System (ADS)

    Katsuro-Hopkins, Oksana; Sabbagh, S. A.; Bialek, J. M.; Park, H. K.; Kim, J. Y.; You, K.-I.; Glasser, A. H.; Lao, L. L.

    2007-11-01

    Stability to ideal MHD kink/ballooning modes and the resistive wall mode (RWM) is investigated for the KSTAR tokamak. Free-boundary equilibria that comply with magnetic field coil current constraints are computed for monotonic and reversed shear safety factor profiles and H-mode tokamak pressure profiles. Advanced tokamak operation at moderate to low plasma internal inductance shows that a factor of two improvement in the plasma beta limit over the no-wall beta limit is possible for toroidal mode number of unity. The KSTAR conducting structure, passive stabilizers, and in-vessel control coils are modeled by the VALEN-3D code and the active RWM stabilization performance of the device is evaluated using both standard and advanced feedback algorithms. Steady-state power and voltage requirements for the system are estimated based on the expected noise on the RWM sensor signals. Using NSTX experimental RWM sensors noise data as input, a reduced VALEN state-space LQG controller is designed to realistically assess KSTAR stabilization system performance.

  3. 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.

  4. 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.

  5. Robust control of long-pulse, high performance plasmas in KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Jeon, Youngmu; Hahn, S. H.; Han, H. S.; Woo, M. H.; Joung, M.; Kim, Jayhyun; Bae, Y. S.; Kim, H.-S.; Yoon, S. W.; Oh, Y. K.; Na, Y. S.; Eidietis, N. W.; Walker, M. L.; Lanctot, M. J.; Hyatt, A. W.; Mueller, D. A.; Kstar Team

    2016-10-01

    The goal of KSTAR is to achieve and demonstrate high performance, steady state tokamak operations in long pulse up to 300 s. In recent years, we made significant progresses on plasma control and performance for this advanced tokamak (AT) operation. First of all, the plasma equilibrium magnetic control has been substantially improved by applying fully decoupled multi-input-multi-output (MIMO) isoflux shape controllers [1]. The MIMO shape controllers were designed using a newly developed design method by taking the plasma equilibrium response into account self-consistently. More than eight shape control variables including plasma currents are controlled independently on each other with high accuracy (less than 1cm error on average) and with wide variations of plasma shape. By virtue of this robust control, various long pulse H-mode discharges have been operated up to 60 s, which was the maximum pulse length allowable in current KSTAR system. Also, plasma performance has been improved accordingly. A fully non-inductive H-mode operation [1] was achieved for the first time in KSTAR, through the so-called `high betap' operation with betap 3.0. In addition, various experimental attempts for advanced scenario development have been conducted such as the `hybrid' [2] and `high li' scenarios[3].

  6. 1.5 GHz single-photon detection at telecommunication wavelengths using sinusoidally gated InGaAs/InP avalanche photodiode.

    PubMed

    Namekata, Naoto; Adachi, Shunsuke; Inoue, Shuichiro

    2009-04-13

    We report a telecom-band single-photon detector for gigahertz clocked quantum key distribution systems. The single-photon detector is based on a sinusoidally gated InGaAs/InP avalanche photodiode. The gate repetition frequency of the single-photon detector reached 1.5 GHz. A quantum efficiency of 10.8 % at 1550 nm was obtained with a dark count probability per gate of 6.3 x 10(-7) and an afterpulsing probability of 2.8 %. Moreover, the maximum detection rate of the detector is 20 MHz.

  7. The new 1.2 T{endash}14.5 GHz Caprice source of multicharged ions: Results with metallic elements

    SciTech Connect

    Hitz, D.; Bourg, F.; Delaunay, M.; Ludwig, P.; Melin, G.; Pontonnier, M.; NGuyen, T.K.

    1996-03-01

    The 1.2 T{endash}14.5 GHz ECR Caprice source is an upgrade version of previous Caprice sources where the three main ingredients of an ECR ion source of multicharged ions have been optimized: (i) the magnetic configuration has higher axial fields (1.4{endash}1.45 T at the mirror throats) and radial field (1.05 T at the wall inside the plasma chamber) as well as higher mirror ratios, (ii) the 14.5 GHz rf frequency is convenient to higher magnetic fields, and (iii) more efficient electron sources allow the electron density to reach higher values, and thus high extracted ion currents (both first stage and wall coating). Emphasis is given to the metallic elements, the source is able to produce 10 e{mu}A of Ca{sup 14+}, 3 e{mu}A of Fe{sup 17+} and Ni{sup 20+}, 1 e{mu}A of U{sup 37+}, while being able to deliver 1130 e{mu}A of O{sup 6+}, 190 e{mu}A of O{sup 7+}, and 100 e{mu}A of Ar{sup 12+}. {copyright} {ital 1996 American Institute of Physics.}

  8. Study of Divertor Heat Patterns Induced by LHCD L-Mode Plasmas Using an Infra-Red Camera System on EAST

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Gan, Kaifu; Gong, Xianzu; Zhang, Xiaodong; Wang, Fumin; Yang, Zhendong; Chen, Meiwen; Wang, Xiaoqiong

    2015-10-01

    Divertor heat patterns induced by Lower Hybrid Current Drive (LHCD) L-mode plasmas are investigated using an infra-red (IR) camera system on an Experimental Advanced Superconducting Tokamak (EAST). A two-dimensional finite element analysis code DFlux is used to compute heat flux along the poloidal divertor target and corresponding quantities. Outside the Origin Strike Zone (OSZ), a Second Peak Heat Flux (SPHF) zone, where the heat flux is even stronger than that at the OSZ, appears on the lower-outer (LO) divertor plates with LHCD and disappears immediately after switching off the LHCD. The main heat-flux shifts from the SPHF zone towards the OSZ when the divertor configuration converts from double null to lower single null, indicating that the growth of the SPHF zone is apparently affected by a plasma magnetic configuration. The heat patterns on the LO divertor plates are observed to be different from that on the lower-inner (LI) targets as the SPHF zone appears only on the LO divertor target. It is also found that the heat flux at the SPHF zone was obviously enhanced after the Supersonic Molecule Beam Injection (SMBI) pulse. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2014GB101001 and 2014GB101002)

  9. Effect of thickness on microwave absorptive behavior of La-Na doped Co-Zr barium hexaferrites in 18.0-26.5 GHz band

    NASA Astrophysics Data System (ADS)

    Arora, Amit; Narang, Sukhleen Bindra; Pubby, Kunal

    2017-02-01

    In this research, the microwave properties of Lanthanum-Sodium doped Cobalt-Zirconium barium hexaferrites, intended as microwave absorbers, are analyzed on Vector Network Analyzer in K-band. The results indicate that the doping has resulted in lowering of real permittivity and enhancement of dielectric losses. Real permeability has shown increase while magnetic losses have shown decrease in value with doping. All these four properties have shown very small variation with frequency in the scanned frequency range which indicates the relaxation type of behavior. Microwave absorption characteristics of these compositions are analyzed with change in sample thickness. The results demonstrate that the matching frequency of the microwave absorber shifts towards lower side of frequency band with increase in thickness. The complete analysis of the prepared microwave absorbers shows a striking achievement with very low reflection loss and wide absorption bandwidth for all the six compositions in 18-26.5 GHz frequency band.

  10. Design and assessment of a robust voltage amplifier with 2.5 GHz GBW and >100 kGy total dose tolerance

    NASA Astrophysics Data System (ADS)

    Verbeeck, J.; Leroux, P.; Steyaert, M.

    2011-01-01

    A differential voltage amplifier with a gain-bandwidth product of 2.5Ghz and using adaptive biasing has been designed in a standard CMOS technology and assessed under radiation and temperature variations. The principle used in this ASIC will be employed in the design of a Gbps TIA with improved tolerance for γ-irradiation and temperature for an optical instrumentation (LIDAR) receiver aiming at operation in harsh environments. The voltage amplifier was tested under gamma radiation and features a gain degradation of merely 4.5% up to a total dose of 100kGy. In order to verify the radiation effects on the IC, the threshold voltage shift of the separate transistors has been investigated. Temperature characterization has shown that the amplifier features a reduction of the voltage gain by only 5.6% for a temperature range of -40 till 130 °C.

  11. 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.

  12. 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.

  13. 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.

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

    PubMed

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

    2010-10-01

    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(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.

  15. Measurement and simulation of stilbene scintillator response for the KSTAR neutron diagnostic system

    NASA Astrophysics Data System (ADS)

    Lee, Seung Kyu; Son, Jae Bum; Kang, JeongSoo; Seo, Hee; Won, Byung-Hee; Park, Se-Hwan; Kim, Ho-Dong; Kang, Byoung Hwi; Kim, Gi Dong; Kim, Yong Kyun

    2014-03-01

    The Korea Superconducting Tokamak Advanced Research (KSTAR) project was started in December 1995, and its construction was completed in August 2007. On June 13, 2008, the KSTAR successfully produced its first plasma, and the diagnostic systems played an important role in achieving the first successful plasma operation. In fact, various diagnostic systems are required to protect reactor devices, to the control plasma, and to evaluate the plasma's performance in fusion reactors. One of the most essential tools for control of the burning plasma in fusion reactors may be a neutron diagnostic system to prove the presence of the plasma by measuring the neutrons from fusion reactions directly. The stilbene scintillator has been proposed as a good candidate for a neutron diagnostic system in the KSTAR fusion reactor because the stilbene scintillator is well-known to be an excellent material for detection of fast neutrons in a high gamma-ray background environment. If fast-neutron spectra are to be measured amid a high gamma-ray background, especially-designed electronics are necessary. For instance, a digital charge pulse shape discrimination (PSD) method, utilizing a total-to-partial-charge-ratio analysis, discriminates neutron from gamma-ray signals. Also, a flash analog-to-digital convertor (FADC) with a field-programmable gate array (FPGA) increases the data-transfer rate for real-time evaluation of plasma performance. In the present study, measurements and simulations were performed in order to confirm the stilbene scintillator's response to D-D fusion reaction neutrons. Additionally, the count-rate limit of the neutron diagnostic system was determined by using measurements with a 252Cf source at different distances.

  16. Numerical simulation on edge localized mode control capability of resonant magnetic perturbation in the KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Kim, Doohyun; Han, Hyunsun; Kim, Ki Min; Park, Jong Kyu; Jeon, Young Mu; Na, Yong-Su; Hong, Sang Hee

    2010-09-01

    Numerical simulations are carried out to investigate the applicability of resonant magnetic perturbation (RMP) to KSTAR plasmas for a possible control of edge localized mode (ELM) to suppress or mitigate its damages to divertor materials. For the verification of the feasibility of RMP application, magnetic island configurations, resonant normal fields, magnetic island widths and Chirikov parameters are calculated for two types of KSTAR operation scenarios: steady state and hybrid. Field error correction (FEC) coils in KSTAR are considered to produce externally perturbed magnetic fields for RMP, and the directions of coil currents determine the toroidal mode n and the parity (even or odd). The RMP configurations are described by vacuum superposition of the equilibrium magnetic fields and the perturbed ones induced by FEC coils. The numerical simulations for n = 2 toroidal mode in both operation scenarios show that when the pitches of the equilibrium and perturbed magnetic fields are well aligned, magnetic islands are formed for a series of m poloidal modes and the adjacent islands are overlapped to generate a stochastic layer in the edge region. Even parity turns out to be more effective in making the magnetic islands overlapped to become stochastic field lines in the steady-state operation, while odd parity in the hybrid operation. The formation of the stochastic layer is verified by the calculated Chirikov parameters, which also give basic information on the current requirement of FEC coils. Additionally, lobe structures of stochastic field lines are found in the edge region extended to the divertor plate in the hybrid scenario. Based on the standard vacuum criteria for RMP, the simulation results indicate that the FEC coils will be feasible for control of ELMs and mitigation of divertor heat load by RMP in both steady-state and hybrid operation scenarios.

  17. Digital I/Q demodulation for KSTAR ion cyclotron range of frequency system

    SciTech Connect

    Wang, S. J.; Kwak, J. G.; Hwang, C. K.

    2009-02-15

    An ion cyclotron range of frequency system requires rf diagnostics for a rf-plasma coupling or for maintaining a correct operation. A detector based on a digital I/Q demodulation technique collects the rf amplitude and phase at the same time without errors from the I/Q imbalance inherent in an analog counterpart. The theory of such a detector was studied and implemented for the first campaign of the KSTAR tokamak. Experimental results of the rf and other diagnostics are presented and discussed.

  18. Digital I/Q demodulation for KSTAR ion cyclotron range of frequency system.

    PubMed

    Wang, S J; Kwak, J G; Hwang, C K

    2009-02-01

    An ion cyclotron range of frequency system requires rf diagnostics for a rf-plasma coupling or for maintaining a correct operation. A detector based on a digital I/Q demodulation technique collects the rf amplitude and phase at the same time without errors from the I/Q imbalance inherent in an analog counterpart. The theory of such a detector was studied and implemented for the first campaign of the KSTAR tokamak. Experimental results of the rf and other diagnostics are presented and discussed.

  19. Long-lived pressure-driven coherent structures in KSTAR plasmas

    SciTech Connect

    Lee, S. G. Seol, J.; Lee, H. H.; Aydemir, A. Y.; Terzolo, L.; Lee, K. D.; Bae, Y. S.; Bak, J. G.; Choe, G. H.; Yun, G. S.; Yoo, J. W.

    2016-05-15

    Highly coherent structures associated with an extremely long-lived saturated magnetohydrodynamic instability have been observed in KSTAR tokamak under a long-pulse and steady-state operation. They persist essentially unchanged for the full duration of a discharge up to 40 s, much longer than any dynamical or dissipative time scales in the system. Analysis of the data, supported by numerical simulations, indicates that they may be associated with a pressure-driven mode causing some degradation in the toroidal rotation, electron, and ion energy confinement.

  20. Impurity diagnosis of a KSTAR graphite divertor tile using laser induced breakdown spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Kim, Minju; Cho, Min Sang; Cho, Byoung Ick

    2017-04-01

    Laser induced breakdown spectroscopy (LIBS) has been tested to diagnose impurity elements on a Korea Superconducting Tokamak Advanced Research (KSTAR) divertor tile. Spectral lines of various impurity elements such as iron, chromium, and nickel were detected from the divertor surface. The variation of spectra with consecutive laser pulses demonstrates the potential for depth profiling analysis for the deposited impurity layer. The LIBS plasma parameters have been qualitatively determined from analysis of the relative line intensities and linewidths for each element. The validity of this analysis has been checked with atomic spectral simulations.

  1. Lesson from Tungsten Leading Edge Heat Load Analysis in KSTAR Divertor

    NASA Astrophysics Data System (ADS)

    Hong, Suk-Ho; Pitts, Richard Anthony; Lee, Hyeong-Ho; Bang, Eunnam; Kang, Chan-Soo; Kim, Kyung-Min; Kim, Hong-Tack; ITER Organization Collaboration; Kstar Team Team

    2016-10-01

    An important design issue for the ITER tungsten (W) divertor and in fact for all such components using metallic plasma-facing elements and which are exposed to high parallel power fluxes, is the question of surface shaping to avoid melting of leading edges. We have fabricated a series of tungsten blocks with a variety of leading edge heights (0.3, 0.6, 1.0, and 2.0 mm), from the ITER worst case to heights even beyond the extreme value tested on JET. They are mounted into adjacent, inertially cooled graphite tile installed in the central divertor region of KSTAR, within the field of view of an infra-red (IR) thermography system with a spatial resolution to 0.4 mm/pixel. Adjustment of the outer divertor strike point position is used to deposit power on the different blocks in different discharges. The measured power flux density on flat regions of the surrounding graphite tiles is used to obtain the parallel power flux, q|| impinging on the various W blocks. Experiments have been performed in Type I ELMing H-mode with Ip = 600 kA, BT = 2 T, PNBI = 3.5 MW, leading to a hot attached divertor with typical pulse lengths of 10 s. Three dimensional ANSYS simulations using q|| and assuming geometric projection of the heat flux are found to be consistent with the observed edge loading. This research was partially supported by Ministry of Science, ICT, and Future Planning under KSTAR project.

  2. 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.

  3. Quiescence of magnetic braking and control of 3D non-resonance in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, J.-K.; in, Y.; Jeon, Y. M.; Logan, N. C.; Wang, Z. R.; Menard, J. E.; Kim, J. H.; Ko, W. H.; Kstar Team

    2016-10-01

    Magnetic braking using non-axisymmetric (3D) field is a promising tool to control rotation in tokamaks and thereby micro-to-macro instabilities. Ideally magnetic braking should induce only neoclassical momentum transport, without provoking resonant instabilities or unnecessary perturbations in particle or heat transport. Indeed in KSTAR, it was shown that the 3 rows of internal coils could be used to generate highly non-resonant n =1 with backward-helicity field distribution, called -90 phasing, and to change rotation without any perturbations to other transport channels. Recent KSTAR experiments, however, have also shown that the broad-wavelength field distribution, called 0 phasing, is rather more quiescent whereas -90 phasing can be highly degrading especially in high q95 plasmas. IPEC and NTV modeling are consistent with both observations, and further provide the optimal point in coil phasing and amplitude space. Additional experiments and comparisons with modeling all imply the sensitivity of plasma response to remnant resonant field, and thus importance of non-resonance control, to accomplish quiescent magnetic braking. This work was supported by DOE Contract DE-AC02-09CH11466.

  4. 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.

  5. The On-Site Status of the Kstar Helium Refrigeration System

    NASA Astrophysics Data System (ADS)

    Chang, H.-S.; Park, D. S.; Joo, J. J.; Moon, K. M.; Cho, K. W.; Kim, Y. S.; Bak, J. S.; Kim, H. M.; Cho, M. C.; Kwon, I. K.; Fauve, E.; Bernhardt, J.-M.; Dauguet, P.; Beauvisage, J.; Andrieu, F.; Yang, S.-H.; Baguer, G. M. Gistau

    2008-03-01

    Since the first design of the KSTAR helium refrigeration system (HRS) in year 2000, many modifications and changes have been applied due to both system optimization and improved knowledge of the KSTAR cold components. The present specification of the HRS had been fixed on March, 2005. Consequent manufacturing of main equipment, such as "Compressor Station" (C/S), "Cold Box" (C/B), and "Distribution Box ♯1" (D/B ♯1) was completed by or under the supervision of Air Liquide DTA by the end of year 2006. The major components of the C/S are 2 low and 2 high pressure compressor units and an oil-removal system. The cooling power of the C/B at 4.5 K equivalent is 9 kW achieved by using 6 turbo-expanders. The D/B ♯1 is a cryostat housing 49 cryogenic valves, 2 supercritical helium circulators, 1 cold compressor, and 7 heat exchangers immersed in a 6 m3 liquid helium storage. In this proceeding, the on-site installation and commissioning status of the HRS will be presented. In addition, the final specification and design features of the HRS and the

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

    PubMed

    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. 2D Simulations of KSTAR edge plasma using SOLPS 4.3 code

    NASA Astrophysics Data System (ADS)

    Shim, Seung Bo; Kotov, Vladislav; Reiter, Detelev; Han, Hyunsun; Kim, Jin Yong; Na, Yong-Su; Lee, Hae June

    2012-10-01

    Control of plasma density and impurity content is crucial to achieve high performance long pulse operation in tokamaks. In this paper edge plasma scenarios of KSTAR are analyzed numerically. ITER version of the well-known SOLPS code package (SOLPS4.3) which comprises 2D multi-species fluid plasma code B2 and 3D Monte-Carlo particle solver EIRENE coupled self-consistently. This latter allows full kinetic neutral particle transport modeling in realistic geometries including pump ducts and leaks to the main vessel from the sub-divertor volumes. Both connected and disconnected double null configurations are investigated. The main focus is made on studying the sensitivity of the edge plasma parameters with respect to gas puffing rate (density scans), thus, effectiveness of this latter for the plasma control. Preliminary findings show that for the reference KSTAR pumps: total pumping speed 100 m^3/s, pumping rates up to 13 Pa.m^3/s, and high performance discharges with heating power 8 MW plasma in both divertors is likely to stay attached. At the same time, plasma temperature at the divertor targets as well as the peak incident heat flux density can be effectively reduced with increased gas puff, been especially sensitive in the inner divertors.

  8. Suppression of edge localized mode crashes by multi-spectral non-axisymmetric fields in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, Jayhyun; Park, Gunyoung; Bae, Cheonho; Yoon, Siwoo; Han, Hyunsun; Yoo, Min-Gu; Park, Young-Seok; Ko, Won-Ha; Juhn, June-Woo; Na, Yong Su; The KSTAR Team

    2017-02-01

    Among various edge localized mode (ELM) crash control methods, only non-axisymmetric magnetic perturbations (NAMPs) yield complete suppression of ELM crashes beyond their mitigation, and thus attract more attention than others. No other devices except KSTAR, DIII-D, and recently EAST have successfully achieved complete suppression with NAMPs. The underlying physics mechanisms of these successful ELM crash suppressions in a non-axisymmetric field environment, however, still remain uncertain. In this work, we investigate the ELM crash suppression characteristics of the KSTAR ELMy H-mode discharges in a controlled multi-spectral field environment, created by both n=2 middle reference and n=1 top/bottom proxy in-vessel control coils. Interestingly, the attempts have produced a set of contradictory findings, one expected (ELM crash suppression enhancement with the addition of n  =  1 to the n  =  2 field at relatively low heating discharges) and another unexpected (ELM crash suppression degradation at relatively high heating discharges) from the earlier findings in DIII-D. This contradiction indicates the dependence of the ELM crash suppression characteristics on the heating level and the associated kink-like plasma responses. Preliminary linear resistive MHD plasma response simulation shows the unexpected suppression performance degradation to be likely caused by the dominance of kink-like plasma responses over the island gap-filling effects.

  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 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.

  11. Linear global gyrokinetic simulations of toroidal Alfven eigenmodes in KSTAR plasmas

    NASA Astrophysics Data System (ADS)

    Shahzad, M.; Rizvi, H.; Ryu, C. M.

    2016-12-01

    Excitation of toroidal Alfven eigenmodes (TAEs) in KSTAR tokamak plasmas has been studied by using the GENE code. Verification and benchmark analysis are performed for Alfven eigenmodes (AEs) excited by the energetic particles (EPs) in comparison with the AEs from the GYGLES code, and excellent agreements are found. In addition, the threshold value of the EP density gradient to destabilize the TAE has been investigated. For the plasma equilibrium of KSTAR discharge (10574), TAEs of n = 2 are found to be excited by coupling of adjoining poloidal harmonics (5, 6), (6, 7), and (7, 8). The dependence of the growth rate and frequency of the TAE on the EP density gradient is examined. It is found that the threshold value of EP density gradient increases with the higher poloidal mode coupling, of which location moves outward in the radial direction. The growth rates of TAEs with higher poloidal mode numbers are smaller than those with lower poloidal mode numbers, indicating that perpendicular wavenumbers play an important role. The efficiency of the EP drive for the TAE decreases for a higher poloidal mode coupling. At a higher EP density gradient, TAEs with higher poloidal harmonics are less unstable due to the decrease in the radial extents of the modes.

  12. Non-linear MHD Simulation of ELMs including Pellet Triggered ones for KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; Park, G.; Strauss, H.; Kim, J. Y.

    2011-10-01

    Three-dimensional non-linear MHD simulations have been conducted to investigate the qualitative characteristics of ELM(Edge Localized Mode)s including pellet induced ones using the M3D code. A linearized velocity perturbation of initial equilibrium is employed to trigger the ELM instability for the simulation of natural ELM, while a density blob, which represents the ionized pellet ablation and is located within the edge pedestal, is adopted in an adiabatic condition for that of pellet induced one. The initial equilibrium is constructed based on a H-mode plasma of KSTAR(Korea Superconducting Tokamak Advanced Research) device. It is found that characteristics of natural ELM simulation are in qualitative agreement with the experimental observations including that density perturbation is much larger than temperature one during ELM instability. Regarding the pellet induced ELM, it is observed that the locally increased pressure due to the fast parallel heat conduction compared to the spread of density perturbation triggers the peeling-ballooning instability resulting in ELM-like relaxation. Detailed results will be presented in the discussion of underlying mechanism and application to KSTAR tokamak.

  13. Simulations of plasma shape and vertical-instability control in KSTAR

    NASA Astrophysics Data System (ADS)

    Lodestro, L. L.; Bulmer, R. H.; Meyer, W. H.; Pearlstein, L. D.

    2012-10-01

    In recent years, prompted by applications to ITER, the Corsica code's capability for evolving free-boundary equilibria coupled to transport, in particular current-profile transport, has been improved. All active and passive material conductors (coils, conducting plates, vessel walls) in these calculations are represented as axisymmetric wires, coupled to each other and the plasma with circuit equations; up/down asymmetric elongated plasmas require a feedback circuit to control the vertical instability. The improvements include: completion of the facility for running Corsica as the plasma model in Matlab/Simulink simulations of the circuits, benchmarked against stand-alone Corsica simulations; development of a general machine-description data-base for importing or verifying a machine's conductor configurations; and modernization and generalization of the (scripted) algorithms that accomplish the couplings in Corsica, plus new features needed for ITER scenario development. The code has been used to assess the capability of ITER's in-vessel coils (VS3) and is presently being used for ITER control simulations. In this paper, we apply the code to KSTAR. We have updated the KSTAR machine description and will present simulations of plasma-shape and vertical-instability control.

  14. Relative performance of 8.5-GHz and 32-GHz telemetry links on the basis of total data return per pass

    NASA Technical Reports Server (NTRS)

    Koerner, M. A.

    1986-01-01

    The performance of X-band (8.5-GHz) and 32-GHz telemetry links is compared on the basis of the total data return per DSN station pass. Differences in spacecraft transmitter efficiency, transmit circuit loss, and transmitting antenna area efficiency and pointing loss are not considered in these calculations. Thus, the performance differentials calculated in this memo are those produced by a DSN 70-m station antenna gain and clear weather receiving system noise temperature and by weather. These calculations show that, assuming mechanical compensation of the DSN 70-m antenna for 32-GHz operation, a performance advantage for 32 GHz over X-band of 8.2 dB can be achieved for at least one DSN station location. Even if only Canberra and Madrid are used, a performance advantage of 7.7 dB can be obtained for at least one DSN station location. A system using a multiple beam feed (electronic compensation) should achieve similar results.

  15. 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.

  16. A 3.5-4.5 GHz Complementary Metal-Oxide-Semiconductor Ultrawideband Receiver Frontend Low-Noise Amplifier with On-Chip Integrated Antenna for Interchip Communication

    NASA Astrophysics Data System (ADS)

    Azhari, Afreen; Kimoto, Kentaro; Sasaki, Nobuo; Kikkawa, Takamaro

    2010-04-01

    Chip-to-chip ultrawideband (UWB) wireless interconnections are essential for reducing resistance capacitance (RC) delay in wired interconnections and three-dimensional (3D) highly integrated packaging. In this study, we demonstrated a wireless interchip signal transmission between two on-chip meander antennas on printed circuit board (PCB) for 1 to 20 mm transmission distances where the low power gain of each antenna due to a lossy Si substrate has been amplified by a low-noise amplifier (LNA). The measured result shows that the LNA produces 26 dB of improvement in antenna power gain at 4.5 GHz on a lossy Si substrate. Moreover, a Gaussian monocycle pulse with a center frequency of 2.75 GHz was also received by an on-chip antenna and amplified by the LNA. The LNA was integrated with an on-chip antenna on a Si substrate with a resistivity of 10 Ω·cm using 180 nm complementary metal-oxide-semiconductor (CMOS) technology. The investigated system is required for future single chip transceiver front ends, integrated with an on-chip antenna for 3D mounting on a printed circuit (PC) board.

  17. 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.

  18. The influence of the reflective environment on the absorption of a human male exposed to representative base station antennas from 300 MHz to 5 GHz.

    PubMed

    Vermeeren, G; Gosselin, M C; Kühn, S; Kellerman, V; Hadjem, A; Gati, A; Joseph, W; Wiart, J; Meyer, F; Kuster, N; Martens, L

    2010-09-21

    The environment is an important parameter when evaluating the exposure to radio-frequency electromagnetic fields. This study investigates numerically the variation on the whole-body and peak spatially averaged-specific absorption rate (SAR) in the heterogeneous virtual family male placed in front of a base station antenna in a reflective environment. The SAR values in a reflective environment are also compared to the values obtained when no environment is present (free space). The virtual family male has been placed at four distances (30 cm, 1 m, 3 m and 10 m) in front of six base station antennas (operating at 300 MHz, 450 MHz, 900 MHz, 2.1 GHz, 3.5 GHz and 5.0 GHz, respectively) and in three reflective environments (a perfectly conducting wall, a perfectly conducting ground and a perfectly conducting ground + wall). A total of 72 configurations are examined. The absorption in the heterogeneous body model is determined using the 3D electromagnetic (EM) finite-difference time-domain (FDTD) solver Semcad-X. For the larger simulations, requirements in terms of computer resources are reduced by using a generalized Huygens' box approach. It has been observed that the ratio of the SAR in the virtual family male in a reflective environment and the SAR in the virtual family male in the free-space environment ranged from -8.7 dB up to 8.0 dB. A worst-case reflective environment could not be determined. ICNIRP reference levels not always showed to be compliant with the basic restrictions.

  19. Real-time EFIT data reconstruction based on neural network in KSTAR

    NASA Astrophysics Data System (ADS)

    Kwak, Sehyun; Jeon, Youngmu; Ghim, Young-Chul

    2014-10-01

    Real-time EFIT data can be obtained using a neural network method. A non-linear mapping between diagnostic signals and shaping parameters of plasma equilibrium can be established by the neural network, particularly with the multilayer perceptron. The neural network is utilized to attain real-time EFIT data for Korea Superconducting Tokamak for Advanced Research (KSTAR). We collect and process existing datasets of measured data and EFIT data to train and test the neural network. Parameter scans such as the numbers of hidden layers and hidden units were performed in order to find the optimal condition. EFIT data from the neural network was compared with both offline EFIT and real-time EFIT data. Finally, we discuss advantages of using neutral network reconstructed EFIT data for real time plasma control.

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

    PubMed

    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. 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.

  2. Observation of the loss of pre-disruptive runaway electrons in KSTAR ohmic plasma disruptions

    NASA Astrophysics Data System (ADS)

    Cheon, MunSeong; Kim, Junghee; An, YoungHwa; Seo, Dongcheol; Kim, Hyunseok

    2016-12-01

    A newly-developed fast neutron detector revealed a close relationship between the loss of pre-disruptive runaway electrons and the plasma disruption in KSTAR ohmic plasmas. It is observed that a burst of photoneutrons is generated exactly before the start of thermal quenches, indicating a bunch of runaway electrons which had existed before the disruption impacts the first wall at the time. The loss of runaway electrons could be identified also as a decrease in the measured electron temperature, forming a typical two-stage thermal quench trace. From the MHD pattern in the neutron signal during a low-q disruption, it could be identified that pre-disruptive runaway electrons are localized in the plasma, especially on the q  =  2 drift surface. These new findings suggest the pre-disruptive runaway electrons might play an important role in the plasma disruption mechanism.

  3. 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.

  4. ECE imaging of modified edge localized modes (ELMs) under n=1 magnetic perturbations in KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, Jaehyun; Yun, G. S.; Kim, M.; Choi, M. J.; Lee, W.; Park, H. K.; Lee, J. H.; Jeon, Y. M.; Domier, C. W.; Luhmann, N. C., Jr.; Donné, A. J. H.

    2012-10-01

    In order to control the ELMs in KSTAR H-mode plasmas, magnetic perturbations (MPs) of toroidal mode number n=1 were introduced through three sets of field error correction (FEC) coils [1] during the 2011 campaign. The plasma response was studied in 2-D using electron cyclotron emission imaging (ECEI) diagnostic [2], which showed alteration of both the spatial structure and temporal dynamics of the ELMs. The characteristics of the ELMs such as the growth rate, filament size, and poloidal flow are compared before and after the n=1 MP for various configurations of the FEC coil currents. In particular, the ELM suppression by resonant MP condition is characterized by occasional (non-periodic) tiny transport events, which involve the appearance and crash of transient filament structure localized near the separatrix.[4pt] [1] Y. Jeon et al., accepted for publication in Phys. Rev. Lett.[0pt] [2] G.S. Yun et al., Phys. Rev. Lett., 107, 045004 (2011).

  5. 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.

  6. VUV spectroscopy in impurity injection experiments at KSTAR using prototype ITER VUV spectrometer

    NASA Astrophysics Data System (ADS)

    Seon, C. R.; Hong, J. H.; Song, I.; Jang, J.; Lee, H. Y.; An, Y. H.; Kim, B. S.; Jeon, T. M.; Park, J. S.; Choe, W.; Lee, H. G.; Pak, S.; Cheon, M. S.; Choi, J. H.; Kim, H. S.; Biel, W.; Bernascolle, P.; Barnsley, R.

    2017-08-01

    The ITER vacuum ultra-violet (VUV) core survey spectrometer has been designed as a 5-channel spectral system so that the high spectral resolving power of 200-500 could be achieved in the wavelength range of 2.4-160 nm. To verify the design of the ITER VUV core survey spectrometer, a two-channel prototype spectrometer was developed. As a subsequent step of the prototype test, the prototype VUV spectrometer has been operated at KSTAR since the 2012 experimental campaign. From impurity injection experiments in the years 2015 and 2016, strong emission lines, such as Kr xxv 15.8 nm, Kr xxvi 17.9 nm, Ne vii 46.5 nm, Ne vi 40.2 nm, and an array of largely unresolved tungsten lines (14-32 nm) could be measured successfully, showing the typical photon number of 1013-1015 photons/cm2 s.

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

    PubMed

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

    2010-10-01

    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.

  8. Development of Plasma Equilibrium Response Model for Optimized Plasma Control of KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Jeon, Youngmu; Park, Jong-Kyu; Park, Young-Seok; Hwang, Y. S.

    2004-11-01

    Plasma equilibrium response models for an optimized control system design are developed with KSTAR tokamak configurations. In a simple filament model, plasma column is assumed as a single ring filament with rigid displacements, and constitutes circuits with external conductors (coils, passive plate, and vacuum vessel segments). Perturbed equilibrium response model, based on CREATE-L deformable plasma response model [1], assumes that the plasma evolves through a sequence of MHD equilibria. Prediction characteristics of both models are described in terms of open loop characteristics of vertical motion of plasma, and validated by comparison with TSC (Tokamak Simulation Code) simulations. Additionally, applications of the plasma equilibrium response models to design of optimal plasma controllers are described. [1] R. Albanese, and F. Villone, Nucl. Fusion 38 723 (1998)

  9. 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.

  10. a Study on Design Optimization of Conical Bolt in the TF Coil Structure of the Kstar Tokamak

    NASA Astrophysics Data System (ADS)

    Kwon, Young-Doo; Lee, Dae-Suep

    The goals of the KSTAR project are to develop a steady-state-capable advanced superconducting Tokamak and establish a scientific and technological basis for a Korean nuclear fusion power station. The KSTAR Tokamak comprises a magnet system, vacuum vessel, and cryostat, thereby facilitating vacuum conditions for plasma gas at high temperatures, along with low-temperature helium gas for cooling. The TF coil structure, a part of the magnet system, is constructed and jointed with 16 pieces at 22.5-degree intervals using a conical bolt and shear key. The main function of the conical bolt in the inner and outer inter-coil structures is to resist the in-plane and out-of-plane forces and increase the toroidal and intercoil shear stiffness. Therefore, the conical bolt must be dimensionally optimized to reduce the stresses at each connecting part. Accordingly, shape optimization of the conical bolt was carried out using SZGA, and the stresses were analyzed by ANSYS.

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

  14. 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.

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

    PubMed

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

    2012-09-01

    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.

  16. 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

  17. Confinement and ELM characteristics of H-mode plasmas in KSTAR

    NASA Astrophysics Data System (ADS)

    Ahn, J.-W.; Kim, H.-S.; Park, Y. S.; Terzolo, L.; Ko, W. H.; Park, J.-K.; England, A. C.; Yoon, S. W.; Jeon, Y. M.; Sabbagh, S. A.; Bae, Y. S.; Bak, J. G.; Hahn, S. H.; Hillis, D. L.; Kim, J.; Kim, W. C.; Kwak, J. G.; Lee, K. D.; Na, Y. S.; Nam, Y. U.; Oh, Y. K.; Park, S. I.

    2012-11-01

    The latest results of confinement and edge-localized mode (ELM) characteristics of Korea Superconducting Tokamak Advanced Research (KSTAR) H-mode plasmas are reported. The estimation of fast ion contribution to the total stored energy, calculated by both the NUBEAM and ASTRA simulations, and of the effective total heating power is used to derive the thermal energy confinement time (τE,thermal), which is compared with a multi-machine database. The measured power threshold for the L-H transition (Pthr) as a function of density shows a roll-over with minimum value at \\bar{n}_e \\sim 2\\times 10^{19}\\,m^{-3} . KSTAR H-mode plasmas exhibit three distinctive types of ELMs: large type-I ELMs, intermediate ELMs and a mixed (type-I and small ELM peaks) ELM regime. Power scans show that the frequency of the large ELMs increases with increasing heating power, a feature of type-I ELMs. The quality of confinement is higher for type-I and mixed ELMy H-mode (H98(y,2) ˜ 0.9-1) than for the intermediate ELM regime (H98(y,2) ˜ 0.7). Type-I ELMs have precursor-like signals from the magnetics measurement, while the other two ELM types do not. The low-field side (LFS) profile of electron temperature (Te), from the ECE measurement, and the pedestal profile of the toroidal velocity (Vt), from charge-exchange spectroscopy, show a continuous build up on the LFS during the inter-ELM period. However, the pedestal ion temperature (Ti) remains unchanged for most of the inter-ELM period until it rapidly rises in the last stage of the ELM cycle (⩾70-80%). The estimated electron pedestal collisionality for a type-I ELMy regime is v_e^\\ast \\sim 0.5{{--}}0.6 . The confinement and ELM characteristics for the ELM suppression discharges by the application of an n = 1 magnetic perturbation (MP) have also been investigated for each of the identified stages during the MP application. A second L-H transition during the L-mode phase after the end of first H-mode stage occurs for some discharges

  18. KSTAR equilibrium operating space and projected stabilization at high normalized beta

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    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 0.83 kW 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

  19. 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

  20. MSE measurements for sawtooth and non-inductive current drive studies in KSTAR

    NASA Astrophysics Data System (ADS)

    Ko, J.; Park, H.; Bea, Y. S.; Chung, J.; Jeon, Y. M.

    2016-10-01

    Two major topics where the measurement of the magnetic-field-line rotational transform profiles in toroidal plasma systems include the long-standing issue of complete versus incomplete reconnection model of the sawtooth instability and the issue with future reactor-relevant tokamak devices in which non-inductive steady state current sustainment is essential. The motional Stark effect (MSE) diagnostic based on the photoelastic-modulator (PEM) approach is one of the most reliable means to measure the internal magnetic pitch, and thus the rotational transform, or its reciprocal (q), profiles. The MSE system has been commissioned for the Korea Superconducting Tokamak Advanced Research (KSTAR) along with the development of various techniques to minimize systematic offset errors such as Faraday rotation and mis-alignment of the bandpass filters. The diagnostic has revealed the central q is well correlated with the sawtooth oscillation, maintaining its value above unity during the MHD quiescent period and that the response of the q profile to external current drive such as electron cyclotron wave injection not only involves the local change of the pitch angle gradient but also a significant shift of the magnetic topology due to the wave energy transport. Work supported by the Ministry of Science, ICT and Future Planning, Korea.

  1. First evidence of Alfvén wave activity in KSTAR plasmas

    NASA Astrophysics Data System (ADS)

    Hole, M. J.; Ryu, C. M.; Woo, M. H.; Bak, J. G.; Sharapov, S. E.; Fitzgerald, M.; the KSTAR Team

    2013-04-01

    We report on first evidence of wave activity during neutral beam heating in KSTAR plasmas: 40 kHz magnetic fluctuations with a toroidal mode number of n = 1. Our analysis suggests this a beta-induced Alfvén eigenmode (BAE) resonant with the q = 1 surface. A kinetic analysis, when coupled with electron temperature measurements from electron cyclotron emission and ion/electron temperature ratios from crystallography, enables calculation of the frequency evolution, which is in agreement with observations. Complementary detailed magnetohydrodynamic (MHD) modelling of the magnetic configuration and wave modes supports the BAE conclusion, by locating an n = 1 mode separated from the continuum in the core region. Finally, we have computed the threshold to marginal stability for a range of ion temperature profiles. These suggest the BAE can be driven unstable by energetic ions when the ion temperature radial gradient is sufficiently large. Our findings suggest that mode existence could be used as a form of inference for temperature profile consistency in the radial interval of the mode, thereby extending the tools of MHD spectroscopy.

  2. Effect of RMP spectrum on ELM suppression and the divertor plasma in KSTAR

    NASA Astrophysics Data System (ADS)

    Ahn, Joon-Wook; Park, J.-K.; in, Y.; Loarte, A.; Kim, J.; Jeon, Y. M.; Park, G. Y.; Choe, W.; Hong, J. H.; Hong, S. H.; Lee, H. H.; Kang, C. S.; Ko, W. H.; Yoon, S. W.

    2016-10-01

    ELM suppression by n =1 and n =2 magnetic perturbations have been robustly obtained in KSTAR, and effects of various coil configurations for applied magnetic perturbations (MPs) on ELM suppression as well as divertor plasma conditions have been investigated. The 4 toroidal and 3 poloidal sectors of internal coils allow to fully scan the phase difference (Δφ) of n =1 between different rows of coils, where it is shown that ideal plasma response can either shield or amplify applied MPs, depending on Δφ , which leads respectively to the weakening and strengthening of divertor footprint striations compared to the vacuum case. On the other hand, shielding is found to be the dominant plasma response for all possible cases of n =2 configuration (Δφ =0o and 90o, and mid-plane coil only), which weakens footprint striations. Spectra of applied MPs have been varied by changing Δφ as well as modifying the ratio of coil currents between different row of coils, e.g. IU/IL, in order to find optimal conditions for ELM suppression and divertor heat and particle flux dispersal. Effects of divertor conditions in various density and impurity levels on the ELM behavior and footprint striations are also being investigated. Work supported by the U.S. DOE, contract # DE-AC05-00OR22725.

  3. Intrinsic rotation reversal, non-local transport, and turbulence transition in KSTAR L-mode plasmas

    NASA Astrophysics Data System (ADS)

    Shi, Y. J.; Kwon, J. M.; Diamond, P. H.; Ko, W. H.; Choi, M. J.; Ko, S. H.; Hahn, S. H.; Na, D. H.; Leem, J. E.; Lee, J. A.; Yang, S. M.; Lee, K. D.; Joung, M.; Jeong, J. H.; Yoo, J. W.; Lee, W. C.; Lee, J. H.; Bae, Y. S.; Lee, S. G.; Yoon, S. W.; Ida, K.; Na, Y.-S.

    2017-06-01

    Experiments of electron cyclotron resonance heating (ECH) power scan in KSTAR tokamak clearly demonstrate that both the cutoff density for non-local heat transport (NLT) and the threshold density for intrinsic rotation reversal can be determined by the collisionality. We demonstrate that NLT can be affected by ECH, and the intrinsic rotation direction follows the changes of NLT. The cutoff density of NLT and threshold density for rotation reversal can be significantly increased by ECH. The poloidal flow of turbulence in core plasma is in the electron and the ion diamagnetic direction in ECH plasmas and high density OH plasma, respectively. The auto-power spectra of density fluctuation are almost the same in the outer region for both ECH and OH plasmas. On the other hand, the divergence in density fluctuation spectra at high frequency range between OH and ECH plasma is clearly observed in core region. The features of linear confinement and saturated confinement also appeared in ECH plasma, which is similar to the linear ohmic confinement (LOC) mode and saturate ohmic confinement (SOC) mode. All these observations in macroscopic parameters and micro fluctuations suggest a possible link between the macro phenomena and the structural changes in turbulence mode.

  4. 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.

  5. First comprehensive particle balance study in KSTAR with a full graphite first wall and diverted plasmas

    NASA Astrophysics Data System (ADS)

    Yu, Yaowei; Hong, Suk-Ho; Yoon, Si-Woo; Kim, Kwang-Pyo; Kim, Woong-Chae; Park, Jae-Min; Oh, Young-Suk; Na, Hoon-Kyun; Bak, Jun-Gyo; Chung, Kyu-Sun; the KSTAR Team

    2012-10-01

    The first comprehensive particle balance study is carried out in the KSTAR 2010 campaign with a full graphite first wall and diverted plasmas. The dominant retention is observed during the gas puffing into the plasmas. Statistical analysis shows that deuterium retention is increased with the number of injected particles. Particle balance analysis in the whole campaign shows that the long-term retention ratio is ˜21%, and the retention via implantation can be partially recovered by He-glow discharge cleaning (GDC), while long-term retention via co-deposition. The wall pumping capability is decreased with the D2 plasma due to fuel accumulation in the first wall, and He-GDC is effective in recovering the wall pumping. Boronization assisted by the D2 glow discharge using C2B10H12 strongly enhances the wall puffing and leads to negative retentions, but the wall pumping capability is recovered in 2-3 days by He-GDCs. Electron cyclotron resonance heating enhances wall outgassing during the discharge. During a diverted H-mode discharge, the retention rate decreases to a very low value, and a high divertor particle flux of ˜1.5 × 1023 D s-1 is observed indicating the strong recycling divertor. The amount of recovered deuterium after discharges mainly depends on the plasma-wall interaction when the plasma is terminated, and disruptive discharges release more particles from the first wall.

  6. Control of core argon impurity profile by ECH in KSTAR L-mode plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Joohwan; Lee, Seung Hun; Kim, Juhyung; Seon, C. R.; Lee, S. G.; Park, G. Y.; Lee, K. D.; Henderson, S. S.; Lee, H. Y.; Park, Jae Sun; Jang, Juhyeok; Jang, Siwon; Jeon, Taemin; O'Mullane, M.; Choe, Wonho

    2015-06-01

    Experiments on trace argon impurity transport in L-mode discharges were performed on Korea superconducting tokamak advanced research (KSTAR) with electron cyclotron resonance heating (ECH). Ar emission was measured by soft x-ray (SXR) arrays and vacuum UV (VUV) diagnostics. A significant reduction in the core Ar emissivity was observed with core ECH. The reduction was the largest with on-axis heating and became smaller with outward heating positions. The diffusivity and convection velocity of Ar were obtained by analysis of the SXR data with the SANCO impurity transport code for the on-axis ECH and the non-ECH shots. In the on-axis ECH case, both diffusivity and convection velocity increased. Furthermore, the convection changed its direction from inward to outward in the plasma core (r/a < 0.3), resulting in a hollow profile of the total Ar density. Together with the reduction in the SXR signals, the hollow impurity profile in the core and the reversal of the convection velocity consistently confirm that ECH can reduce impurity accumulation in the core region. Neoclassical impurity transport and linear stability of micro-turbulence were calculated and discussed in relation to the possible transport mechanism.

  7. Modification of argon impurity transport by electron cyclotron heating in KSTAR H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Joohwan; Henderson, S. S.; Kim, Kimin; Seon, C. R.; Song, Inwoo; Lee, H. Y.; Jang, Juhyeok; Park, Jae Sun; Lee, S. G.; Lee, J. H.; Lee, Seung Hun; Hong, Suk-Ho; Choe, Wonho

    2017-03-01

    Experiments with a small amount of Ar gas injection as a trace impurity were conducted in the Korea Superconducting Tokamak Advanced Research (KSTAR) H-mode plasma ({{B}\\text{T}}   =  2.8 T, {{I}\\text{P}}   =  0.6 MA, and {{P}\\text{NBI}}   =  4.0 MW). 170 GHz electron cyclotron resonance heating (ECH) at 600 and 800 kW was focused along the mid-plane with a fixed major radial position of R   =  1.66 m. The emissivity of the Ar16+ (3.949 {\\mathring{\\text{A}}} ) and Ar15+ (353.860 {\\mathring{\\text{A}}} ) spectral lines were measured by x-ray imaging crystal spectroscopy (XICS) and a vacuum UV (VUV) spectrometer, respectively. ECH reduces the peak Ar15+ emission and increases the Ar16+ emission, an effect largest with 800 kW. The ADAS-SANCO impurity transport code was used to evaluate the Ar transport coefficients. It was found that the inward convective velocity found in the plasma core without ECH was decreased with ECH, while diffusion remained approximately constant resulting in a less-peaked Ar density profile. Theoretical results from the NEO code suggest that neoclassical transport is not responsible for the change in transport, while the microstability analysis using GKW predicts a dominant ITG mode during both ECH and non-ECH plasmas.

  8. 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.

  9. Analysis of MHD instabilities limiting high normalized beta operation in KSTAR

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    H-mode plasma operation in KSTAR reached high normalized beta up to 4.3 that significantly surpassed the computed n = 1 ideal no-wall beta limit by a factor of 1.6. Pulse lengths at maximum normalized beta were extended to longer pulses by new, more rapid equilibrium control resulting in normalized beta greater than 3 sustained for 1 s. Analysis of these plasmas shows that low- n global kink/ballooning or resistive wall modes (RWMs) were not the cause of the plasma termination. Kinetic modification of the ideal MHD n = 1 stability criterion computed by the MISK code shows the kinetic RWM to be stable, which is consistent with the observed high normalized beta operation. An m/ n = 2/1 tearing mode onsets at high normalized beta greater than 3 that experimentally reduces normalized beta by more than 30%. The stability of the observed 2/1 tearing mode examined by using the M3D-C1 code coupled with the EFIT reconstruction shows a stable 2/1 mode while the equilibrium is experimentally unstable to the 2/1 mode This result may imply that the mode is classically stable, and the pressuredriven neoclassical terms dominate over the current gradient term. Advances in the analysis from the recent run campaign will be reported. Supported by U.S. DOE Grant DE-FG02-99ER54524.

  10. Reconstruction of Plasma Equilibria and Projected Stabilization of Global MHD Modes in KSTAR

    NASA Astrophysics Data System (ADS)

    Park, Y. S.; Sabbagh, S. A.; Bialek, J. M.; Berkery, J. W.; Jeon, Y. M.; Hahn, S. H.; Lee, S. G.; You, K.-. I.; Park, H. K.; Evans, T. E.; Eidietis, N.; Walker, M.; Leuer, J.

    2010-11-01

    Experimental equilibria of the KSTAR tokamak with plasma current up to 0.34 MA were reconstructed using EFIT. Vessel currents were included by fitting estimated values based on loop voltage measurements and effective resistances from 2 and 3-D vacuum model calculations including a double-walled vessel with large port penetrations and passive stabilizers. Active and passive stabilization of global MHD instabilities for operation above the no-wall beta limit is also projected. The stabilization is applied using a set of segmented internal coils called in-vessel control coils (IVCCs). Passive stability of the resistive wall mode and power requirement for its active stabilization are investigated including conductive casing structures covering the IVCC, and noise effects. The potential for ELM mitigation by resonant magnetic perturbations is also examined by using the TRIP3D code. Favorable configurations of the IVCC based on the Chirikov parameter are determined using a combination of all IVCCs (midplane and off-midplane coils) with a dominant n = 2 field configuration.

  11. Validation of BOUT + + ELM simulation by Comparison with ECEI Measurements in the KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Kim, Minwoo; Lee, Jaehyun; Choi, Minjun; Yun, Gunsu; Xu, X. Q.; Lee, Woochang; Park, Hyeon; Domier, C. W.; Luhmann, N. C., Jr.; Kstar Team

    2013-10-01

    Details of ELM dynamics has been measured in 2D using an electron cyclotron emission imaging (ECEI) diagnostic in the KSTAR tokamak. The observed ELM dynamics show complex evolution stages including linear growth, saturation, changes in mode number and rotation velocity, and localized crash. We studied the mode structure of the observed ELMs in the linear growth phase using 3-field BOUT + + simulations. The toroidal mode number (n) of ELMs, which was experimentally determined by an array of toroidal Mirnov coils, was fixed in the simulation. On the other hand, the pressure profile was adjusted to make the linear growth rate finite at the given n number. For direct comparison with the observed images, the simulation results were converted to synthetic ECEI images by taking into account instrumental broadening, intrinsic ECE broadening in the pedestal region, and system noises. The synthetic images were qualitatively well matched with the observations. As a next step, a simulation study in linear phase is planned for a self-consistent equilibrium including bootstrap current. Work supported by NRF Korea under contract no. 2013035905 and US DoE under contract no. DE-FG-02-99ER54531.

  12. Equilibrium and global MHD stability study of KSTAR high beta plasmas under passive and active mode control

    NASA Astrophysics Data System (ADS)

    Katsuro-Hopkins, O.; Sabbagh, S. A.; Bialek, J. M.; Park, H. K.; Bak, J. G.; Chung, J.; Hahn, S. H.; Kim, J. Y.; Kwon, M.; Lee, S. G.; Yoon, S. W.; You, K.-I.; Glasser, A. H.; Lao, L. L.

    2010-02-01

    The Korea Superconducting Tokamak Advanced Research, KSTAR, is designed to operate a steady-state, high beta plasma while retaining global magnetohydrodynamic (MHD) stability to establish the scientific and technological basis of an economically attractive fusion reactor. An equilibrium model is established for stability analysis of KSTAR. Reconstructions were performed for the experimental start-up scenario and experimental first plasma operation using the EFIT code. The VALEN code was used to determine the vacuum vessel current distribution. Theoretical high beta equilibria spanning the expected operational range are computed for various profiles including generic L-mode and DIII-D experimental H-mode pressure profiles. Ideal MHD stability calculations of toroidal mode number of unity using the DCON code shows a factor of 2 improvement in the wall-stabilized plasma beta limit at moderate to low plasma internal inductance. The planned stabilization system in KSTAR comprises passive stabilizing plates and actively cooled in-vessel control coils (IVCCs) designed for non-axisymmetric field error correction and stabilization of slow timescale MHD modes including resistive wall modes (RWMs). VALEN analysis using standard proportional gain shows that active stabilization near the ideal wall limit can be reached with feedback using the midplane segment of the IVCC. The RMS power required for control using both white noise and noise taken from NSTX active stabilization experiments is computed for beta near the ideal wall limit. Advanced state-space control algorithms yield a factor of 2 power reduction assuming white noise while remaining robust with respect to variations in plasma beta.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2014-06-01

    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* of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α* 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.

  15. Two-Dimensional Visualization of Growth and Burst of the Edge-Localized Filaments in KSTAR H-Mode Plasmas

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    The filamentary nature and dynamics of edge-localized modes (ELMs) in the KSTAR high-confinement mode plasmas have been visualized in 2D via electron cyclotron emission imaging. The ELM filaments rotating with a net poloidal velocity are observed to evolve in three distinctive stages: initial linear growth, interim quasisteady state, and final crash. The crash is initiated by a narrow fingerlike perturbation growing radially from a poloidally elongated filament. The filament bursts through this finger, leading to fast and collective heat convection from the edge region into the scrape-off layer, i.e., ELM crash.

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

    PubMed

    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

    2014-06-01

    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* of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α* 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.

  17. SOL-Divertor Plasma Simulation in the KSTAR Tokamak with a Neutral Transport Model Using the TEP method

    NASA Astrophysics Data System (ADS)

    Han, Hyun-Sun; Kim, Ki Min; Hong, Sang Hee

    2007-11-01

    A two-dimensional numerical simulation has been carried out to analyze the transport phenomena of plasma and neutrals in Scrape- off Layer (SOL) and divertor region of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. In this numerical work, the transmission and escape probability (TEP) method is used for a neutral transport model by adapting the GTNEUT [1] code, which is coupled with a plasma transport model based on the Braginskii's fluid formulation. Prior to combining the GTNEUT code with the plasma transport one, preliminary tests are conducted by comparison with a Monte Carlo method to check the numerical accuracy and efficiency of the neutral model. A performance improvement of computing time is achieved during the coupling processes by pre-computing the various transmission coefficients and setting up an interpolation lookup table. As results of the simulation, plasma density and temperature distributions in the SOL-divertor region are calculated for the baseline operation of the KSTAR tokamak. This integrated modeling method could be extended to the simulation of more complicated edge transport for the advanced tokamak operation including impurity transport. [1] J. Mandrekas, Comput. Phys. Comm., 161, 36 (2004)

  18. 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.

  19. Direct measurements of safety factor profiles with motional Stark effect for KSTAR tokamak discharges with internal transport barriers

    NASA Astrophysics Data System (ADS)

    Ko, J.; Chung, J.

    2017-06-01

    The safety factor profile evolutions have been measured from the plasma discharges with the external current drive mechanism such as the multi-ion-source neutral beam injection for the Korea Superconducting Tokamak Advanced Research (KSTAR) for the first time. This measurement has been possible by the newly installed motional Stark effect (MSE) diagnostic system that utilizes the polarized Balmer-alpha emission from the energetic neutral deuterium atoms induced by the Stark effect under the Lorentz electric field. The 25-channel KSTAR MSE diagnostic is based on the conventional photoelastic modulator approach with the spatial and temporal resolutions less than 2 cm (for the most of the channels except 2 to 3 channels inside the magnetic axis) and about 10 ms, respectively. The strong Faraday rotation imposed on the optical elements in the diagnostic system is calibrated out from a separate and well-designed polarization measurement procedure using an in-vessel reference polarizer during the toroidal-field ramp-up phase before the plasma experiment starts. The combination of the non-inductive current drive during the ramp-up and shape control enables the formation of the internal transport barrier where the pitch angle profiles indicate flat or slightly hollow profiles in the safety factor.

  20. Comparative ELM study between the observation by ECEI and linear/nonlinear simulation in the KSTAR plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Minwoo; Park, Hyeon K.; Yun, Gunsu; Lee, Jaehyun; Lee, Jieun; Lee, Woochang; Jardin, Stephen; Xu, X. Q.; Kstar Team

    2015-11-01

    The modeling of the Edge-localized-mode (ELM) should be rigorously pursued for reliable and robust ELM control for steady-state long-pulse H-mode operation in ITER as well as DEMO. In the KSTAR discharge #7328, a linear stability of the ELMs is investigated using M3D-C1 and BOUT + + codes. This is achieved by linear simulation for the n = 8 mode structure of the ELM observed by the KSTAR electron cyclotron emission imaging (ECEI) systems. In the process of analysis, variations due to the plasma equilibrium profiles and transport coefficients on the ELM growth rate are investigated and simulation results with the two codes are compared. The numerical simulations are extended to nonlinear phase of the ELM dynamics, which includes saturation and crash of the modes. Preliminary results of the nonlinear simulations are compared with the measured images especially from the saturation to the crash. This work is supported by NRF of Korea under contract no. NRF-2014M1A7A1A03029865, US DoE by LLNL under contract DE-AC52-07NA27344 and US DoE by PPPL under contract DE-AC02-09CH11466.

  1. Role of the equilibrium and perturbative core current density in sawtoothing and non-sawtoothing discharges in KSTAR

    NASA Astrophysics Data System (ADS)

    Nam, Yoonbum; Park, Hyeon; Choi, Minjun; Choe, Gyuenghyuen; Lee, Woochang; Yun, Gunsu; Jardin, Stephen

    2015-11-01

    New study of multimode physics in the core of the KSTAR plasma provides an opportunity to address the long standing issue of the central current density during sawooth crash. The recent experiment on excitation of the m/n =3/3 mode with a current blip induced by ECH and successive evolution to the m/n =2/2 and m/n =1/1 mode during one sawtooth period in the core of the sawtoothing discharge in KSTAR suggests that the central safety factor (q0) may have to change from below ~ 1 (before crash) to slightly above ~ 1(after crash). This interpretation is consistent with the q profile condition for MHD simulation necessary for the growth of the higher order modes which require q0 slightly above ~ 1 until the 1/1 mode becomes dominant. Experimental observation of a long lived higher order mode in non-sawtoothing discharge (presumably q0>1) is consistent with the fact that the q0 has to be below ~ 1 to support the growth of the m/n =1/1 mode. Supported by the NRF of Korea under Contract No. NRF-2014M1A7A1A03029881 and NRF-2014M1A7A1A03029865 and by U.S. DOE grant DE-FG02-99ER54524.

  2. Advanced operation scenarios toward high-beta, steady-state plasmas in KSTAR

    NASA Astrophysics Data System (ADS)

    Yoon, Si-Woo; Jeon, Y. M.; Woo, M. H.; Bae, Y. S.; Kim, H. S.; Oh, Y. K.; Park, J. M.; Park, Y. S.; Kstar Team

    2016-10-01

    For the realization of the fusion reactor, solving issues for high-beta steady-state operation is one of the essential topics for the present superconducting tokamaks and in this regard, KSTAR has been focusing on maximizing performance and increasing pulse length simultaneously. Typically, study on high beta operation has been focusing on advanced scenario limited at relatively short pulse discharge and partial success has been reported previously. However, it must be stressed that it is critical to verify compatibility of the developed scenario to long-pulse operation and compared with that of the short-pulse, it is turned out stable long-pulse operation is possible only with a reduced level of beta. In this work, the results of recent approaches in long-pulse operation are presented focusing respectively on high betaN, high betap and high li scenarios. For high betaN, the achieved level is close to 3 with Ip =0.4 MA, BT =1.4T and Pext 6MW and it is found to be limited by m/n =2/1 tearing mode and is also sensitive on the internal inductance. For high betap, conditions of the maximum betap is investigated mainly by parametric scans of plasma current (Ip =0.4-0.7 MA) and also neutral beam injection power (3-5MW). The achieved betap is also close to 3 with Ip =0.4 MA, BT =2.9T and Pext 6MW and it is found to be limited by heating power and without indication of MHD activities. Finally, attempt for high li discharge will be addressed on scenario development and transient results.

  3. Second Harmonic 110 GHz ECH-assisted Start-up in KSTAR

    NASA Astrophysics Data System (ADS)

    Joung, M.; Gorelov, Y.; Park, S.; Jeong, J. H.; Bae, Y. S.; Yang, H. L.; Kim, J. H.; Han, S. H.; Kwak, J. G.; Lohr, J.

    2012-09-01

    In KSTAR device, a 110 GHz ECH system has been a useful heating device for a stable plasma start-up because a pure ohmic discharge scenario with a limited loop voltage of about 4 V was sometimes not successful for burn-through and plasma current ramp-up due to inconsistent wall conditioning and density control. Even though a pure ohmic discharge also was successful, the application of X2-mode ECH could reduce the flux consumption of poloidal field coils, leading to long pulse discharges. The ECH power was injected at the time of the field null formation after the onset of the toroidal electric field in which the electron temperature significantly increased up to 100 eV so that burn-through is overcome. The ECH heating enabled the formation of close flux surfaces earlier, leading to the reliable plasma current ramp-up, but, it caused outward plasma movement and failure of the plasma control, resulting in loss of the discharge. Moreover, impurities from the plasma facing components caused by not fully absorbed ECH power had a detrimental effect on the H-mode transition. In ECH-assisted start-up in the ramp-up phase, ECH power was mainly used for central electron heating, leading to reduction of the flux consumption of the central coils by increasing the electron temperature along with a density increase in the ramp-up phase. When X2-mode ECH power of 350 kW was injected at the mid-plane with a toroidal angle of 10 degree for 1 sec after the onset of the loop voltage, the flux consumption was reduced by about 30% in comparison with the pure ohmic discharges.

  4. Investigation of instabilities and rotation alteration in high beta KSTAR plasmas

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    H-mode plasma operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) device has been expanded to significantly surpass the ideal MHD no-wall beta limit. Plasmas with high normalized beta, βN, up to 4.3 have been achieved with reduced plasma internal inductance, li, to near 0.7, exceeding the computed n = 1 ideal no-wall limit by a factor of 1.6. Pulse lengths at maximum βN were extended to longer pulses by new, more rapid control. The stability of the observed m/n = 2/1 tearing mode that limited the achieved high βN is computed by the M3D-C1 code, and the effect of sheared toroidal rotation to tearing stability is examined. As a method to affect the mode stability in high βN plasmas, the non-resonant alteration of the rotation profile by non-axisymmetric magnetic fields has been used, enabling a study of the underlying neoclassical toroidal viscosity (NTV) physics and stability dependence on rotation. Non-axisymmetric field spectra were applied using in-vessel control coils (IVCCs) with varied n = 2 field configurations to alter the plasma toroidal rotation profile in high beta H-mode plasmas and to analyze their effects on the rotation. The rotation profile was significantly altered with rotation reduced by more than 60% without tearing activity or mode locking. To investigate the physical characteristics and scaling of the measured rotation braking by NTV, changes in the rotation profile are analytically examined in steady state. The expected NTV scaling with the square of the normalized applied field perturbation agrees with the measured profile change δB2.1-2.3. The NTV is also found to scale as Ti2.1-2.4, in general agreement with the low collisionality "1/ν" regime scaling of the NTV theory (TNTV-(1/ν) ∝ Ti2.5).

  5. 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

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

    PubMed

    Wiharto, Wiharto; Kusnanto, Hari; Herianto, Herianto

    2016-01-01

    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. 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. 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%. Based on these results it can be concluded that the proposed system is able to deliver good performance in the category of classification.

  7. Solitary perturbations prior to the partial collapse of the edge pedestal in KSTAR H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Lee, J. E.; Yun, G. S.; Kim, M. H.; Kim, M.; Lee, J.; Park, H. K.; Choi, M.; Ko, W. H.; Kstar Team

    2016-10-01

    Solitary perturbations (SPs), localized both poloidally and radially, are frequently observed on the KSTAR tokamak within 100 μs before the partial collapse of the edge pedestal. The perturbation structure measured by 2D imaging diagnostic is clearly distinguished from the quasi-steady filamentary modes that are routinely observed during the inter-crash period. In particular, the SPs have a low toroidal mode number (typically unity) and smaller pitch angle. The SPs are similar to the irregular mode structure with large amplitude appearing near complete crash. The resemblance suggests that the generation of SPs is strongly connected to the crash mechanism. This work is supported by NRF of Korea under contract no. NRF-2014M1A7A1A03029881 and BK21+ program.

  8. Variation of magnetic braking by non-axisymmetric magnetic fields depending on the perturbed field structure in the KSTAR tokamak

    NASA Astrophysics Data System (ADS)

    Kim, Kimin; Jeon, Y. M.; Park, J.-K.; Ko, W. H.; In, Y.; Choe, W.; Kim, J.; Lee, S. G.; Yoon, S. W.; Kwak, J. G.; Oh, Y. K.

    2017-03-01

    The variation of a magnetic braking profile by non-axisymmetric magnetic fields has been experimentally demonstrated and numerically validated in the KSTAR tokamak. Two types of n  =  2 non-resonant magnetic fields were applied by changing the relative phase of non-axisymmetric field coils. One is even parity, of which non-resonant fields deeply penetrate into the plasma core, and the other is odd parity localized at the plasma edge. The even and odd parity produced significantly different perturbed magnetic field structures, and thereby drove global and edge-dominant toroidal rotation damping, respectively. These distinct braking profiles are consistently reproduced by drift-kinetic particle simulations, indicating the possibility of the predictive utilization of non-resonant magnetic fields for rotation profile control.

  9. Determining the Inner Edge of the Habitable Zone Around M and late K-Stars Using 3-D Climate Models

    NASA Astrophysics Data System (ADS)

    Kopparapu, Ravi; Wolf, Eric T.; Haqq-Misra, Jacob; Jun, Yang; Kasting, James; Mahadevan, Suvrath; Terrien, Ryan

    2015-12-01

    We present preliminary results for the inner edge of the habitable zone (HZ) around M and late K-stars, calculated from state of the art 3-D global climate models, the NCAR Community Atmosphere Model and Flexible Modeling System (FMS) developed by the Geophysical Fluid Dynamics. Both 1-D and 3-D models show that, for a water-rich planet, as the surface temperature increases due to increased stellar radiation, water vapor becomes a significant fraction of the atmosphere. M- and late K-stars have their peak flux in the near-infrared, where water is a strong absorber. Our models have been updated with a new radiation scheme and with H2O absorption coefficients derived from the most recent line-by-line databases (HITRAN2012 and HITEMP2010). These updates will most likely result in moving the inner edge of the HZ around M and late-K stars further away from the star than previous estimates. The initial targets for survey missions such as K2 and the Transiting Exoplanet Survey Satellite (TESS) will likely be planets near the inner edge of the HZ due to the increased signal-to-noise ratio that results from their proximity to their host star. The James Webb Space Telescope (JWST) may be capable of probing the atmospheric composition of terrestrial planets around a nearby M-dwarf. Thus, determining the most accurate inner edge of the HZ around M-dwarf stars is crucial for selecting target candidates for atmospheric characterization and to identify potential biomarkers.

  10. 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.

  11. Helicon wave coupling in KSTAR plasmas for off-axis current drive in high electron pressure plasmas

    NASA Astrophysics Data System (ADS)

    Wang, S. J.; Wi, H. H.; Kim, H. J.; Kim, J.; Jeong, J. H.; Kwak, J. G.

    2017-04-01

    A helicon wave current drive is proposed as an efficient off-axis current drive in the high electron β plasmas that are expected in fusion reactors. A high frequency helicon wave coupling was analyzed using the surface impedance at a plasma boundary. A slow wave coupling, which may compete with the helicon wave coupling at a frequency of 500 MHz, is estimated to be lower than the fast wave coupling by an order of magnitude in the KSTAR edge plasma density and in practical Faraday shield misalignment with the magnetic pitch. A traveling wave antenna, which is a two port combline antenna, was analyzed using a simplified lumped element model. The results show that the traveling wave antenna provides load resiliency because of its insensitivity to loading resistance, provided that the loading resistance at a radiating element is limited within a practical range. The combline antenna is attractive because it does not require a matching system and exhibits a high selectivity of parallel refractive index. Based on the analysis, a seven element combline antenna was fabricated and installed at an off-mid-plane offset of 30 cm from the mid-plane in KSTAR. The low power RF characteristics measured during several plasma discharges showed no evidence of slow wave coupling. This is consistent with the expectation made through the surface impedance analysis which predicted low slow wave coupling. The wave coupling to the plasma is easily controlled by a radial outer-gap control and gas puffing. No plasma confinement degradation was observed during the radial outer-gap control of up to 3 cm in H-mode discharges. In a ELMy plasmas, only a small reflection peak was observed during a very short portion of the ELM bursting period. If the number of radiating elements is increased for high power operation, then complete load resiliency can be expected. A very large coupling can be problematic for maintaining a parallel refractive index, although this issue can be mitigated by

  12. Comparison of divertor heat flux splitting by 3D fields with field line tracing simulation in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, Kimin; Ahn, J.-W.; Lee, H. H.; Park, J.-K.; Kang, C. S.; In, Y.; Kwak, J. G.; Yoon, S. W.; Oh, O. K.; Choe, Wonho

    2017-05-01

    We present the experimental and numerical analysis of divertor heat flux spitting by 3D magnetic fields in KSTAR. A dedicated experiment to measure the modification of the divertor heat flux profile in the n = 2 resonant and non-resonant field configurations has been conducted. The measured heat flux profiles were directly compared to the magnetic field line tracing (FLT) simulation using the POCA-FLT code, which fully considers vacuum and ideal plasma response models. Measurements indicate that the 3D fields induce strong splitting of heat flux on the divertor target due to the formation of stochastic field layers. Splitting characteristics largely depend on the applied 3D field structure and its alignment to the axisymmetric magnetic pitch. The modeling of the field line connection length shows good agreement with measurements, reproducing well the pattern of heat flux splitting. Simulations with the ideal plasma response better reproduce measured heat flux profiles by excitation of non-resonant field components in the non-resonant 0° phase and shielding of resonant field components in the resonant 90° phase.

  13. Comparison study between the observed ELM dynamics in the KSTAR H-mode and simulation results from BOUT++

    NASA Astrophysics Data System (ADS)

    Kim, Minwoo; Xu, Xueqiao; Yun, Gunsu S.; Lee, Jaehyun; Park, Hyeon K.

    2012-10-01

    The BOUT++ simulations [1] of edge localized modes (ELMs) have been quantitatively compared with high resolution 2D images of ELMs observed in typical KSTAR H-mode plasmas through an electron cyclotron emission imaging (ECEI) system [2]. The poloidal structure of the most unstable mode predicted by the linear 3-field simulation qualitatively matches with the observed ELM structure. As the next step, simulation studies for the nonlinear aspects of the ELM dynamics are planned; in particular, the transient mode structure change prior to the ELM crash [2] will be investigated. In addition, the parametric dependence of the observed ELM suppression/mitigation process during resonant magnetic perturbation (RMP) [2, 3] and supersonic molecular beam injection (SMBI) experiments will be studied using 5-field BOUT++ simulation.[4pt] [1] X.Q. Xu et al., PRL, 105 (2010).[0pt] [2] G.S. Yun et al., Phys. Plasmas, 19 (2012).[0pt] [3] Y.M. Jeon et al., accepted for publication in PRL.

  14. Characterization of MHD instabilities, plasma rotation alteration, and RWM control analysis in the expanded H-mode operation of KSTAR

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    The Korea Superconducting Tokamak Advanced Research (KSTAR) has expanded its H-mode operational space to higher beta and lower internal inductance, moving toward design target operation. Plasmas have reached normalized beta of 1.9, stored energy of 340 kJ, and energy confinement time of 171ms evaluated by EFIT reconstructions. Advances from the fall run campaign will be reported. Rotating modes having n = 1, 2 tearing parities are observed by internal and external measurements and their characteristics and stability dependence on plasma rotation profile are analyzed and compared to initial observations. Initial alteration of the plasma rotation profile by applied non-axisymmetric fields is investigated and has characteristics of non-resonant braking. Computation of active RWM control using the VALEN code examines the impact of available sensors for control. Both off-axis and midplane sensors are analyzed, and with off-axis sensors the mode can be stabilized up to normalized beta of 4.5 (C/beta = 86/) and up to 3.6 (44&%slash;) with and without compensation of the prompt applied field of the control coils from the sensors, respectively. Power and bandwidth requirements for RWM stabilization are also calculated by including sensor noise and power supply time delay.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Physics-based integrated modeling of the energy confinement time scaling laws for the H- and L-modes in the KSTAR-type tokamak model

    NASA Astrophysics Data System (ADS)

    Kim, J. Y.; Han, H. S.; Terzolo, L.

    2017-07-01

    In an effort to clarify the physics origin of the energy confinement time scaling law in H-mode plasmas, a new analysis method is first proposed where the stored energy is separated into two parts—one coming from the marginal stability with the pedestal boundary condition and the other related to the turbulent dynamics. The method is then applied for the analysis of the global scaling law, as initial examples, focusing on the four parameters of plasma current, input power, magnetic field and density in the KSTAR-type tokamak model. It is shown that the method can provide more quantitative and explicit information on how various physics elements, such as the linear stability, nonlinear turbulent dynamics and pedestal boundary, contribute to the global scaling factor. While this method is not directly applicable, the L-mode is also considered for comparison, trying to clarify how a difference in the scaling law can occur between the H- and L-modes.

  20. 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.

  1. 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.

  2. 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.

  3. The third MIT-Green Bank 5 GHz survey

    SciTech Connect

    Griffith, M.; Heflin, M.; Conner, S.; Lehar, J.; Langston, G. National Radio Astronomy Observatory, Charlottesville, VA )

    1990-09-01

    The third MIT-Green Bank survey, which covers 1.11 sr in the right ascension range from 16.5 h to 5 h between +17 deg and +39.15 deg declination, is presented. The survey is unique in that a sample was observed twice in a short period of time and the spectral indices between 5 and 1.4 GHz are available for most of the sources brighter than 90 mJy. This survey can be used as the starting point for a search for gravitational lenses. The source list can also be examined for clustering and used to estimate the surface density of sources as a function of limiting flux density. 10 refs.

  4. Statistics of the MASIV 5 GHZ VLA Scintillation Survey

    DTIC Science & Technology

    2007-10-01

    with the flatter and more inverted sources more frequently exhibiting scintillation. From planets to dark energy : the modern radio universe 1-5...STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES Proceedings From Planets to Dark Energy : The Modern Radio Universe

  5. LHCD Scenarios for Spherical Tokamak Plasmas

    SciTech Connect

    Takase, Y.; Ejiri, A.; Oosako, T.; Bonoli, P. T.; Wright, J. C.

    2007-09-28

    Noninductive plasma current start-up and sustainment are crucial issues for spherical tokamak reactors and other applications such as component test facility. It is widely recognized that the lower hybrid wave (the slow wave), which is most efficient in driving current, is not accessible to the core of a fully developed spherical tokamak plasma with very high dielectric constant. However, it may be useful in the initial plasma current ramp-up phase while the density is still low, where it is not practical to use other methods of noninductive current drive. Such a possibility is investigated theoretically for planned experiments on the TST-2 spherical tokamak at the University of Tokyo. The transmitters previously used for FWCD experiments on JFT-2M (200 MHz) are being prepared for this experiment. The combline antenna used for JFT-2M has been modified for use in TST-2. This antenna will be used to excite a unidirectional fast wave traveling in the toroidal direction with a toroidal mode number of 12 (corresponding to an initial parallel index of refraction of about 5). The fast wave can mode convert to the lower hybrid wave and drive current under some conditions. Examination of the dispersion relation indicates that there may be a suitable regime at relatively high field (0.3 T) and low density (<1x10{sup 19} m{sup -3})

  6. Implementation of LHCD Experiments on Alcator C-Mod

    SciTech Connect

    Parker, R.; Basse, N.; Beck, W.; Childs, R.; Grimes, M.; Gwinn, D.; Irby, J.; Koert, P.; Labombard, B.; Liptac, J.; Marmar, E.; Terry, D.; Terry, J.; Vieira, R.; Wallace, G.; Wilson, J.R.; Zaks, J.; Bernabei, S.; Ellis, R.; Fredd, E.

    2005-09-26

    An antenna-transmitter system for driving current in the LHRF has been installed in Alcator C-Mod. The antenna is a grill consisting of 4 poloidal rows of waveguides, each with 24 guides in the toroidal direction. Power is supplied by 12 klystrons capable of 250 kW operation at a frequency of 4.6 GHz. Thus the total source power is 3 MW, with about 1.5 MW available to be coupled to the plasma. Power supply and heat throughput limits in C-Mod limit the pulse length to 5 s, which however represents several current redistribution times. With 90 deg. phasing, the n parallel spectrum is sharply peaked at 2.3 and the range 1.5 < n parallel < 3.5 can be accessed dynamically by varying the phase of the klystrons. The system is in the commissioning phase with klystron power limited to {approx}20 kW and pulse length to 10 ms. Early results from plasma operation are discussed.

  7. 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.

  8. 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

  9. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Route, Matthew; Wolszczan, Alexander

    2013-08-01

    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, 3.6σ flare from the L1 dwarf, 2MASS J1439284+192915. This detection is tentative and requires confirmation by additional monitoring observations.

  12. Dual polarization VLBI observations of stellar binary systems at 5 GHz

    NASA Astrophysics Data System (ADS)

    Mutel, R. L.; Lestrade, J. F.; Preston, R. A.; Phillips, R. B.

    1985-02-01

    The binary systems Sigma CrB, SZ Psc, HR 1099, UX Ari, HR 5110, Algol, and Cyg X-1 are characterized in terms of marcsec-scale radio structure on the basis of dual-polarization observations at 4.969-4.997 GHz, obtained with an international VLBI array comprising the 100-m Effelsberg, 36-m Haystack, 42-m Green Bank, 26-m Fort Davis, 130-m-equivalent VLA, and 40-m Owens Valley telescopes (system temperatures 40-70 K) at 22-14 h UT on July 26-27, 1983. The data are presented in graphs and tables and discussed in detail. Single Gaussian brightness distributions with theta(FWHM) = 0.5-2.0 marcsec and brightness temperatures (2-200) x 10 to the 8th K are determined for four sources; core-halo structures are found for UX Ari and Algol; and an upper limit of 50 microarcsec is established for the angular separation of the regions of left and right circular polarization. The gross features seen in RS CVn systems are explained in terms of a simple expanding-coronal-loop model of flare events.

  13. 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.

  14. A cooperative transponder system for improved traffic safety, localizing road users in the 5 GHz band

    NASA Astrophysics Data System (ADS)

    Schaffer, B.; Kalverkamp, G.; Chaabane, M.; Biebl, E. M.

    2012-09-01

    We present a multi-user cooperative mobile transponder system which enables cars to localize pedestrians, bicyclists and other road users in order to improve traffic safety. The system operates at a center frequency of 5.768 GHz, offering the ability to test precision localization technology at frequencies close to the newly designated automotive safety related bands around 5.9 GHz. By carrying out a roundtrip time of flight measurement, the sensor can determine the distance from the onboard localization unit of a car to a road user who is equipped with an active transponder, employing the idea of a secondary radar and pulse compression. The onboard unit sends out a pseudo noise coded interrogation pulse, which is answered by one or more transponders after a short waiting time. Each transponder uses a different waiting time in order to allow for time division multiple access. We present the system setup as well as range measurement results, achieving an accuracy up to centimeters for the distance measurement and a range in the order of hundred meters. We also discuss the effect of clock drift and offset on distance accuracy for different waiting times and show how the system can be improved to further increase precision in a multiuser environment.

  15. Total Ionizing Dose Test Report BFR92A NPN 5 GHz Wide Band Transistor from NXP

    NASA Technical Reports Server (NTRS)

    Phan, Anthony M.; Oldham, Timothy R.

    2011-01-01

    The purpose of this test was to characterize the Philips/NXP BFR92A NPN 5 gigahertz wide band silicon transistor for total dose response. This test shall serves as the radiation lot acceptance test (RLAT) for the lot date code (LDC) 1027. The BFR92A is packaged in a 3-pin plastic SOT23 package. Low dose rate (LDR/ELDRS) irradiations was performed.

  16. 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.

  17. 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.

  18. Intra-day Variability Observations at 5 GHz with the Urumqi 25-meter Radio Telescope

    NASA Astrophysics Data System (ADS)

    Song, H.-G.; Liu, X.

    2007-10-01

    Radio intra-day variability (IDV) in compact flat-spectrum quasars and BL Lac objects has proven to be an important tool to investigate the emission of AGN and the propagation effect in the interstellar medium. We present the preliminary results of Urumqi 25 meter radio telescope IDV searches around some scintillation pulsars. The targets are from JVAS and CLASS samples around five pulsars, J0332+5434, J0826+2637, J1932+1059, J2022+2854, and J2022+5154.

  19. 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.

  20. 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.

  1. An Atlas of Basic Transmission Loss for 0.125 to 15.5 GHz

    DTIC Science & Technology

    1980-08-01

    8217 1. INTRODUCTION Increasing air traffic density and fast, high-flying jets have made reliable navigation and communication systems for aircraft more...ground, isotropic ant.annas, - . O) I0C 12~00 14Z00 I MLCC 1?1500 a- kC’~ .rn ~ vau. s.~ ic~a~ transmission loss versus distance, F’ 100 MhIz, 11 15 00 M... reliability at a higher cost where cost may include a requirement for more frequencies j 110 110 to provide a particular service. Except when Q=0.5, the

  2. 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

    ... period submitted by IEEE 802 and W-Fi Alliance. We find that good cause exist for an extension of the..., IEEE 802 requested that the reply comment deadline be extended by 30 days because in reviewing the... falls before both the 2013 Wi-Fi Alliance Member Meeting and IEEE 802's Plenary Session, and that...

  3. Contemporaneous VLBA 5 GHz Observations of Large Area Telescope Detected Blazars

    DTIC Science & Technology

    2012-01-10

    blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma - ray Space Telescope have been observed contemporaneously by the Very Long...galaxies: jets – galaxies: nuclei – gamma rays : galaxies – radio continuum: galaxies 1. INTRODUCTION The Large Area Telescope (LAT; Atwood et al. 2009...on board the Fermi Gamma - ray Space Telescope is a wide-field telescope covering the energy range from about 20 MeV to more than 300 GeV. It has been

  4. CAD-Based Monte Carlo Neutron Transport KSTAR Analysis for KSTAR

    NASA Astrophysics Data System (ADS)

    Seo, Geon Ho; Choi, Sung Hoon; Shim, Hyung Jin

    2017-09-01

    The Monte Carlo (MC) neutron transport analysis for a complex nuclear system such as fusion facility may require accurate modeling of its complicated geometry. In order to take advantage of modeling capability of the computer aided design (CAD) system for the MC neutronics analysis, the Seoul National University MC code, McCARD, has been augmented with a CAD-based geometry processing module by imbedding the OpenCASCADE CAD kernel. In the developed module, the CAD geometry data are internally converted to the constructive solid geometry model with help of the CAD kernel. An efficient cell-searching algorithm is devised for the void space treatment. The performance of the CAD-based McCARD calculations are tested for the Korea Superconducting Tokamak Advanced Research device by comparing with results of the conventional MC calculations using a text-based geometry input.

  5. Catalog and Atlas from a Sensitive 1.5 GHz Radio Survey Around the North Ecliptic Pole

    DTIC Science & Technology

    1994-02-28

    673000 0.119 6.0 3517 -10 F104 182118.0 650000 0.093 7.5 1614 -1 F105 182152.0 683000 0.106 6.0 2622 -18 F106 182208.0 660000 0.101 6.0 1514 -40 F107 ...F097, F101, F105, F107 , F109. F018: image shifted to include bright source, 2.3’ on western edge not searched; F041: image shifted, 4.6’ on eastern side

  6. Wideband MIMO channel characterization in TV studios and inside buildings in the 2.2-2.5 GHz frequency band

    NASA Astrophysics Data System (ADS)

    Razavi-Ghods, N.; Salous, S.

    2009-10-01

    Multiple input multiple output (MIMO) measurements were performed with a chirp sounder with a switched antenna array at the transmitter and eight parallel receiver channels with 96-MHz bandwidth at 2.25 GHz in TV studios and 240-MHz bandwidth at 2.38 GHz inside buildings. MIMO capacity was estimated from the data with linear and circular arrays with array sizes 2 by 2, 4 by 4, and 6 by 8. Mean capacity estimates for 30-dB signal-to-noise ratio for both line of sight and obstructed line of sight were on the order of 11-31 b/s/Hz for the 2 by 2 to 4 by 4 antenna configurations and for the 6 by 8 directional antenna measurements a median capacity of 50 b/s/Hz. This is an increase of 20 b/s/Hz from the 4 by 4 omnidirectional antenna array indicating diversity gain as well as an increase due to the number of antennas.

  7. 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.

  8. 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.

  9. Microwave ablation of ex vivo human liver and colorectal liver metastases with a novel 14.5 GHz generator.

    PubMed

    Jones, Robert P; Kitteringham, Neil R; Terlizzo, Monica; Hancock, Christopher; Dunne, Declan; Fenwick, Stephen W; Poston, Graeme J; Ghaneh, Paula; Malik, Hassan Z

    2012-01-01

    This study assessed the relationship between time, power and ablation size using a novel high-frequency 14.5 GHz microwave applicator in ex vivo human hepatic parenchyma and colorectal liver metastases. Previous examination has demonstrated structurally normal but non-viable cells within the ablation zone. This study aimed to further investigate how ablation affects these cells, and to confirm non-viability. Ablations were performed in ex vivo human hepatic parenchyma and tumour for a variety of time (10-180 s) and power (10-50 W) settings. Histological examination was performed to assess cellular anatomy, whilst enzyme histochemistry was used to confirm cellular non-viability. Transmission electron microscopy was used to investigate the subcellular structural effects of ablation within these fixed cells. Preliminary proteomic analysis was also performed to explore the mechanism of microwave cell death. Increasing time and power settings led to a predictable and reproducible increase in size of ablation. At 50 W and 180 s application, a maximum ablation diameter of 38.8 mm (±1.3) was produced. Ablations were produced rapidly, and at all time and power settings ablations remained spherical (longest:shortest diameter <1.2). Routine histological analysis using haematoxylin-eosin (H&E) confirmed well preserved cellular anatomy despite ablation. Transmission electron microscopy demonstrated marked subcellular damage. Enzyme histochemistry showed complete absence of viability in ablated tissue. Large spherical ablation zones can be rapidly and reproducibly achieved in ex vivo human hepatic parenchyma and colorectal liver metastases using a 14.5 GHz microwave generator. Despite well preserved cellular appearance, ablated tissue is non-viable.

  10. 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

    2014-12-19

    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.

  11. Left-handed compact MIMO antenna array based on wire spiral resonator for 5-GHz wireless applications

    NASA Astrophysics Data System (ADS)

    Alqadami, Abdulrahman Shueai Mohsen; Jamlos, Mohd Faizal; Soh, Ping Jack; Rahim, Sharul Kamal Abdul; Narbudowicz, Adam

    2017-01-01

    A compact coplanar waveguide-fed multiple-input multiple-output antenna array based on the left-handed wire loaded spiral resonators (SR) is presented. The proposed antenna consists of a 2 × 2 wire SR with two symmetrical microstrip feed lines, each line exciting a 1 × 2 wire SR. Left-handed metamaterial unit cells are placed on its reverse side and arranged in a 2 × 3 array. A reflection coefficient of less than -16 dB and mutual coupling of less than -28 dB are achieved at 5.15 GHz WLAN band.

  12. Characteristics of a large multijunction launcher for high-power LHCD experiments on JT-60U

    SciTech Connect

    Seki, M.; Ikeda, Y.; Ushigusa, K.; Naito, O.; Kondoh, T.; Wolfe, S.W.; Imai, T. )

    1994-10-15

    This paper presents overview of a large multijunction launcher for JT-60U. The launcher is featured by the multijunction module with the oversized taper waveguide, in order to simplify structure of the launcher. This launcher allows high performances of current drive and current profile control by using very sharp and highly directive spectrum. Initial result of coupling property is also described. A good coupling was observed at a power level of [similar to]0.8 MW with plasma-launcher distance of [lt]14 cm.

  13. Calorimetric measurement of heat load in full non-inductive LHCD plasmas on TRIAM-1M

    NASA Astrophysics Data System (ADS)

    Hanada, K.; Shinoda, N.; Sugata, T.; Sasaki, K.; Zushi, H.; Nakamura, K.; Sato, K. N.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Triam Group

    2007-06-01

    Calorimetric measurements using the temperature increment of cooling-water were carried out to estimate the heat load distribution on the plasma facing components (PFCs) in the limiter discharges on TRIAM-1M. Line averaged electron density, ne, and LH power, PLH, dependences of the heat load on PFCs were measured. The heat load on the limiters was proportional to ne1.5 in the range of ne = 0.2-1.0 × 1019 m-3 and PLH1 in the range of PLH = 0.005-0.09 MW. For PLH > 0.1 MW, the plasma transition to an enhanced current drive (ECD) mode appeared and the ne dependences on the heat load on the limiter moderated. This indicates that the heat flux to scrape-off layer (SOL) region was reduced due to the improvement of the plasma confinement. The up-down asymmetry of the heat load on the vacuum vessel was enhanced in the ECD mode, which may be caused by the increasing of the direct loss of energetic electrons.

  14. 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.

  15. 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.

  16. The 1.5 GHz electromagnetic near-field used for cellular phones does not promote rat liver carcinogenesis in a medium-term liver bioassay.

    PubMed

    Imaida, K; Taki, M; Watanabe, S; Kamimura, Y; Ito, T; Yamaguchi, T; Ito, N; Shirai, T

    1998-10-01

    We have recently established that local exposure to a 929.2 MHz electromagnetic near-field, used for cellular phones, does not promote rat liver carcinogenesis in a medium-term bioassay system. In the present study, a 1.439 GHz electromagnetic near-field (EMF), another microwave band employed for cellular phones in Japan, was similarly investigated. Time division multiple access (TDMA) signals for the Personal Digital Cellular (PDC) Japanese cellular telephone standard system were directed to rats through a quarter-wavelength monopole antenna. Numerical dosimetry showed that the peak SARs within the liver were 1.91-0.937 W/kg, while the whole-body average specific absorption rates (SARs) were 0.680-0.453 W/kg, when the time-averaged antenna radiation power was 0.33 W. Exposure was for 90 min a day, 5 days a week, over 6 weeks, to male F344 rats given a single dose of diethylnitrosamine (200 mg/kg, i.p.) 2 weeks previously. At week 3, all rats were subjected to a two-thirds partial hepatectomy. At week 8, the experiment was terminated and the animals were killed. Carcinogenic potential was scored by comparing the numbers and areas of the induced glutathione S-transferase placental form (GST-P)-positive foci in the livers of exposed (48) and sham-exposed rats (48). Despite increased serum levels of corticosterone, adrenocorticotropic hormone (ACTH) and melatonin, the numbers and the areas of GST-P-positive foci were not significantly altered by the exposure. These findings clearly indicated that local body exposure to a 1.439 GHz EMF, as in the case of a 929.2 MHz field, has no promoting effect on rat liver carcinogenesis in the present model.

  17. 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.

  18. A 3 to 5 GHz low-phase-noise fractional-N frequency synthesizer with adaptive frequency calibration for GSM/PCS/DCS/WCDMA transceivers

    NASA Astrophysics Data System (ADS)

    Yaohua, Pan; Niansong, Mei; Hu, Chen; Yumei, Huang; Zhiliang, Hong

    2012-01-01

    A low-phase-noise Σ—Δ fractional-N frequency synthesizer for GSM/PCS/DCS/WCDMA transceivers is presented. The voltage controlled oscillator is designed with a modified digital controlled capacitor array to extend the tuning range and minimize phase noise. A high-resolution adaptive frequency calibration technique is introduced to automatically choose frequency bands and increase phase-noise immunity. A prototype is implemented in 0.13 μm CMOS technology. The experimental results show that the designed 1.2 V wideband frequency synthesizer is locked from 3.05 to 5.17 GHz within 30 μs, which covers all five required frequency bands. The measured in-band phase noise are -89, -95.5 and -101 dBc/Hz for 3.8 GHz, 2 GHz and 948 MHz carriers, respectively, and accordingly the out-of-band phase noise are -121, -123 and -132 dBc/Hz at 1 MHz offset, which meet the phase-noise-mask requirements of the above-mentioned standards.

  19. 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

    .... (a) Operators of NGSO MSS feeder link earth stations and GSO FSS earth stations in the band 29.25 to... MSS feeder link earth station complexes, that will minimize instances of unacceptable interference to the GSO FSS space stations. Earth station licensees operating with GSO FSS systems shall be capable...

  20. 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

    .... (a) Operators of NGSO MSS feeder link earth stations and GSO FSS earth stations in the band 29.25 to... MSS feeder link earth station complexes, that will minimize instances of unacceptable interference to the GSO FSS space stations. Earth station licensees operating with GSO FSS systems shall be capable...

  1. 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

    .... (a) Operators of NGSO MSS feeder link earth stations and GSO FSS earth stations in the band 29.25 to... MSS feeder link earth station complexes, that will minimize instances of unacceptable interference to the GSO FSS space stations. Earth station licensees operating with GSO FSS systems shall be capable...

  2. 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

    .... (a) Operators of NGSO MSS feeder link earth stations and GSO FSS earth stations in the band 29.25 to... MSS feeder link earth station complexes, that will minimize instances of unacceptable interference to the GSO FSS space stations. Earth station licensees operating with GSO FSS systems shall be capable...

  3. Low Phase Noise, 18kHz Frequency Tuning Step, 5GHz, 15bit Digitally Controlled Oscillator in 0.18µm CMOS Technology

    NASA Astrophysics Data System (ADS)

    Pokharel, Ramesh K.; Uchida, Kenta; Tomar, Abhishek; Kanaya, Haruichi; Yoshida, Keiji

    A method to realize the fine frequency-tuning steps using tiny capacitors instead of Metal-Insulator-Metal (MIM) capacitors is proposed for a digitally controlled oscillator (DCO). The tiny capacitors are realized by the coplanar transmission lines which are arranged unsymmetrical in a 6 metal layers (M6) foundry of 0.18µm CMOS technology. These transmission line based capacitors are designed by using electro-magnetic field simulator, and co-designed by using SPICE simulator. Finally, these capacitors are employed to design 15bit DCO and fabricated the proposed DCO in 0.18µm CMOS technology, and tested. The measured phase noise of DCO was -118.3dBc/Hz (@1MHz offset frequency), and the oscillating frequency tuned from 4.86GHz to 5.36GHz in the minimum frequency-tuning step of 18kHz.

  4. Short Range Propagation Measurements at 2.4, 4.5 and 11.5 GHz in Indoor and Outdoor Environments

    DTIC Science & Technology

    1992-05-01

    between the base stations and servers a cable (copper or optical fibre ) can be used as backbone network. The only limitation is that a base station...amplitude and phase values, - the impuls response: a series of time, amplitude and phase values. The data is transfered to an IBM-compatible computer in LOTUS ...the special Hewlett Packard binary format has to be converted to the regular ASCII format that can be read by (for example) the LOTUS software

  5. 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.

  6. Real-time extraction of plasma equilibrium parameters in KSTAR tokamak using statistical methods

    NASA Astrophysics Data System (ADS)

    Na, Yong-Su; Jeon, Young-Mu; Hong, S. H.; Hwang, Y. S.

    2001-02-01

    To improve inherent shortcomings of statistical methods and apply them to the extraction of plasma equilibrium parameters in a fast timescale for real-time plasma control, new concepts of statistical methods such as principal component analysis-based neural network (NN), functional parametrization (FP)-based NN and double network are introduced by modifying NN and FP. These new methods are benchmarked and compared with the conventional techniques of NN and FP in a simple single-filament system. As a result of their applications to identification of plasma equilibrium parameters in the Korea Superconducting Tokamak Advanced Research tokamak, particularly, the double network concept among them has successfully achieved the improvement of drawbacks in the conventional methods. It is shown that more reliable results from the double network method can be obtained by combining several different statistical treatments as a primary network. Even in the case of nonoptimized methods united as a primary network, quite acceptable results can be achieved in the double network method.

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

    PubMed

    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 χ(2) 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 χ(2) method. The best results were obtained for 10(3) training cycles and eight nodes in the hidden layer. Our neural network approach shows good agreement with the χ(2) method and performs the calculation twenty times faster.

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

    SciTech Connect

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

    2016-11-15

    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 χ{sup 2} 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 χ{sup 2} method. The best results were obtained for 10{sup 3} training cycles and eight nodes in the hidden layer. Our neural network approach shows good agreement with the χ{sup 2} method and performs the calculation twenty times faster.

  9. 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.

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

    SciTech Connect

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

    2016-11-15

    Electron cyclotron emission imaging (ECEI) diagnostic on Korean Superconducting Tokamak Advanced Research utilizes quasi-optical heterodyne-detection method to measure 2D (vertical and radial) T{sub e} 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.

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

    SciTech Connect

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

    2016-11-15

    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.

  12. 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.

  13. 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.

  14. Study on an azimuthal line cusp ion source for the KSTAR neutral beam injector.

    PubMed

    Jeong, Seung Ho; Chang, Doo-Hee; In, Sang Ryul; Lee, Kwang Won; Oh, Byung-Hoon; Yoon, Byung-Joo; Song, Woo Sob; Kim, Jinchoon; Kim, Tae Seong

    2008-02-01

    In this study it is found that the cusp magnetic field configuration of an anode bucket influences the primary electron behavior. An electron orbit code (ELEORBIT code) showed that an azimuthal line cusp (cusp lines run azimuthally with respect to the beam extraction direction) provides a longer primary electron confinement time than an axial line cusp configuration. Experimentally higher plasma densities were obtained under the same arc power when the azimuthal cusp chamber was used. The newly designed azimuthal cusp bucket has been investigated in an effort to increase the plasma density in its plasma generator per arc power.

  15. 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.

  16. Field Error Analysis and a Correction Scheme for the KSTAR device

    NASA Astrophysics Data System (ADS)

    You, K.-I.; Lee, D. K.; Jhang, Hogun; Lee, G.-S.; Kwon, K. H.

    2000-10-01

    Non-axisymmetric error fields can lead to tokamak plasma performance degradation and ultimately premature plasma disruption, if some error field components are larger than threshold values. The major sources of the field error include the unavoidable winding irregularities of the poloidal field coils during manufacturing, poloidal field and toroidal field coils misalignments during installation, stray fields from bus and lead wires between coils and power supplies, and welded joints of the vacuum vessel. Numerical simulation results are presented for Fourier harmonics of the error field obtained on the (m,n) = (2,1) resonant flux surface with a coil current set for the reference equilibrium configuration. Field error contributions are considered separately for all major error sources. An error correction scheme designed to reduce key components of the total net error field is also discussed in relation to the field error correction coils inside the vacuum vessel.

  17. 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.

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

    PubMed

    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.

  19. 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.

  20. Revealing the Galactic H II Region G84.9+0.5 through 5 GHz Continuum and Polarization Emission and a Voigt Profile Analysis of Radio Recombination Line Observations

    NASA Astrophysics Data System (ADS)

    Foster, T. J.; Kothes, R.; Kerton, C. R.; Arvidsson, K.

    2007-09-01

    We present new λ = 6 cm radio observations (Stokes I, Q, and U and hydrogen recombination line) of the Galactic object G84.9+0.5, previously classified as a supernova remnant. Radio recombination line (RRL) emission near 6 cm is detected in deep GBT observations, and we are able to separate the 7.6 mK line detected from this object (appearing at vLSR=-40 km s-1) from the line emitted by ionized gas of W80 in the foreground (Tl=5.4 mK; vLSR~0 km s-1) along the same line of sight (LOS). Detection of RRL emission from G84.9+0.5 and the absence of polarized emission at 6 cm imply that this object is an H II region. Rather than a Gaussian, a Voigt function better describes the extended line profile of G84.9+0.5, which has a low-level ``wing'' extending into its negative-velocity end. A Monte Carlo analysis of noisy synthetic spectra is presented, and it is concluded the wing is not spurious. Two physical explanations for the wing (pressure broadening and an outflow of gas) are considered. We favor that of a champagne-type outflow in the gas flowing along the inside wall of a known molecular cloud in the vicinity of the nebula (at -40 km s-1), making G84.9+0.5 a ``blister'' type H II region viewed face-on. We find Te=9900 K and ne=20 cm-3 from a non-LTE analysis of the peak toward the RRL, and a total H II mass of 440 Msolar. A distance of 4.9 kpc is determined for this object. An IR analysis using MSX and 2MASS data is presented, showing H II region colors for G84.9+0.5 and identifying a possible exciting star for this H II region.

  1. Recent progress on TRIAM-1M

    NASA Astrophysics Data System (ADS)

    Zushi, H.; Itoh, S.; Sato, K. N.; Nakamura, K.; Sakamoto, M.; Hanada, K.; Jotaki, E.; Makino, K.; Pan, Y. D.; Kawasaki, S.; Nakashima, H.

    2000-06-01

    A steady state plasma with high performance and high current drive efficiency is reported. In 2.45 GHz LHCD plasmas Ti is studied as a function of ne at the edge of the high ion temperature (HIT) window. Different characteristic timescales are found for Ti and ne to enter the HIT regime and the observed hysteresis behaviour of Ti with respect to ne is attributed to this difference. The electromagnetic emission (<3.5 GHz) is studied in order to understand ion heating mechanisms in the HIT regime. The spectrum shows several sidebands whose peak frequencies correspond to the ion plasma frequency. The spectral narrowing of the width of the sideband shows a clear correlation with ion heating. In 8.2 GHz LHCD plasmas an enhanced current drive (ECD) regime where both current drive efficiency ηCD( = bar neICDR0/PLH ~1 × 1019 A m-2/W) and energy confinement time τE (~8-10 ms) are simultaneously improved is obtained at an bar ne of 4.3 × 1013 cm-3 and B = 7 T under full current drive conditions. There exists a certain threshold power above which the ECD transition occurs. A hysteresis of ηCD is found around the threshold power, which is explained by the different characteristic time for the ECD transition in power rampup and rampdown schemes. Current profile control experiments are performed by using two opposite travelling LHWs. Current compensation (ΔICD/ICD < -10%) is clearly seen when the backward (BW) travelling LHW (8.2 GHz) is added to a target plasma whose current is driven by a forward travelling LHW (8.2 GHz). As the BW wave power is increased, however, the current tends to flow in the forward direction. The mechanisms of this non-linear behaviour of the driven current with respect to the BW wave power are discussed.

  2. 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.

  3. Effects of electron-cyclotron-resonance-heating-induced internal kink mode on the toroidal rotation in the KSTAR Tokamak.

    PubMed

    Seol, J; Lee, S G; Park, B H; Lee, H H; Terzolo, L; Shaing, K C; You, K I; Yun, G S; Kim, C C; Lee, K D; Ko, W H; Kwak, J G; Kim, W C; Oh, Y K; Kim, J Y; Kim, S S; Ida, K

    2012-11-09

    It is observed that the magnitude of the toroidal rotation speed is reduced by the central electron cyclotron resonance heating (ECRH) regardless of the direction of the toroidal rotation. The magnetohydrodynamics activities generally appear with the rotation change due to ECRH. It is shown that the internal kink mode is induced by the central ECRH and breaks the toroidal symmetry. When the magnetohydrodynamics activities are present, the toroidal plasma viscosity is not negligible. The observed effects of ECRH on the toroidal plasma rotation are explained by the neoclassical toroidal viscosity in this Letter. It is found that the neoclassical toroidal viscosity torque caused by the internal kink mode damps the toroidal rotation.

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

    SciTech Connect

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

    2016-11-15

    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.

  5. Magnetic Activity and High Energy XUV Irradiances of Dwarf K-Stars - Impacts of XUV Emissions on Hosted Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Lakatos, S. L.; Voyer, E. N.; Guinan, E. F.; DeWarf, L. E.; Ribas, I.; Harper, G. M.

    2005-05-01

    We report on the study of magnetic activity and spectral X-ray-UV (XUV) irradiances of main-sequence K-type (dK) stars covering a wide range of ages from <0.1 to 10 Gyr and rotation periods of <0.5 - 45d. This study is an extension of the Villanova ``Sun in Time'' Program (see Guinan et al. 2003; Ribas et al. 2005) to cooler, less luminous, but much more numerous, dK stars. These dK stars have deeper convective zones and more efficient magnetic dynamos. Of particular interest is the study of the evolution of coronal and chromospheric XUV emissions of these stars because of the critical roles that these emissions play in the photochemical and photoionization (and possible erosion) of the atmospheres of potentially hosted planets. The extension to dK stars is motivated by the upcoming extrasolar planet search missions (such as Kepler, SIM, and Darwin-TPF) that will search for earth-size planets in the (liquid water) habitable zones of nearby dG, dK and dM stars. Because of the very high space densities of low mass stars, they will likely be discovered to host numerous planets. In this study we have combined our FUSE FUV observations with archival X-ray, EUV, and UV, along with ground-based photometry, to study dependencies of XUV emissions with respect to age and rotation. Here we report on our initial study of a small sample of bright, nearby dK0-5 stars with a wide range of ages and rotation periods. The initial results are presented and we discuss the suitability of low mass dK stars as hosts for planets habitable for life. Also, the long lifetimes and high spacial densities of older dK stars make them attractive targets for searches for advanced intelligent life. This research is supported by NASA/FUSE Grants NAG5-12125, NNG04G038G, and NNGG04GC76G, which we gratefully acknowledge.

  6. E × B flow velocity deduced from the poloidal motion of fluctuation patterns in neutral beam injected L-mode plasmas on KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, W.; Leem, J.; Yun, G. S.; Park, H. K.; Ko, S. H.; Choi, M. J.; Wang, W. X.; Budny, R. V.; Ethier, S.; Park, Y. S.; Luhmann, N. C.; Domier, C. W.; Lee, K. D.; Ko, W. H.; Kim, K. W.

    2016-05-01

    A method for direct assessment of the equilibrium E × B flow velocity ( E ×B flow shear is responsible for the turbulence suppression and transport reduction in tokamak plasmas) is investigated based on two facts. The first one is that the apparent poloidal rotation speed of density fluctuation patterns is close to the turbulence rotation speed in the direction perpendicular to the local magnetic field line within the flux surface. And the second "well-known" fact is that the turbulence rotation velocity consists of the equilibrium E × B flow velocity and intrinsic phase velocity of turbulence in the E × B flow frame. In the core region of the low confinement (L-mode) discharges where a strong toroidal rotation is induced by neutral beam injection, the apparent poloidal velocities (and turbulence rotation velocities) are good approximations of the E ×B flow velocities since linear gyrokinetic simulations suggest that the intrinsic phase velocity of the dominant turbulence is significantly lower than the apparent poloidal velocity. In the neutral beam injected L-mode plasmas, temporal and spatial scales of the measured turbulence are studied by comparing with the local equilibrium parameters relevant to the ion-scale turbulence.

  7. 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

  8. 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.

  9. Effort of lower hybrid current drive experiments toward to H-mode in EAST

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Li, M. H.; Liu, F. K.; Shan, J. F.; Li, Y. C.; Wang, M.; Liu, L.; Zhao, L. M.; Yang, Y.; Wu, Z. G.; Feng, J. Q.; Hu, H. C.; Jia, H.; Cheng, M.; Zang, Q.; Lyu, B.; Duan, Y. M.; Lin, S. Y.; Wu, J. H.; Hillairet, J.; Ekedahl, A.; Peysson, Y.; Goniche, M.; Tuccillo, A. A.; Cesario, R.; Amicucci, L.; Shen, B.; Gong, X. Z.; Xu, G. S.; Zhao, H. L.; Hu, L. Q.; Li, J. G.; Wan, B. N.; EAST Team

    2017-02-01

    Lower hybrid current drive (LHCD) is an effective tool to achieve high confinement (H-mode) plasma in EAST. To utilize LHCD for accessing H-mode plasma, efforts have been made to improve LHW (lower hybrid wave)-plasma coupling and current drive capability at high density. Improved LHW-plasma coupling by means of local gas puffing and gas puffing from the electron side is routinely used during EAST operation with LHCD. High density experiments suggest that low recycling and high LH frequency are preferred for LHCD experiments at high density, consistent with previous results in other machines. The effect of LHCD on the current profile in EAST demonstrates that it is possible to control the plasma profile by optimizing the LHW spectrum. Repeatable H-mode plasma was obtained by LHCD and the maximum density during H-mode with the combination of 2.45 GHz and 4.6 GHz LH waves was up to 4.5  ×  1019 m-3.

  10. 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.

  11. 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.

  12. Time-dependent simulation of lower hybrid current drive in JET discharges

    NASA Astrophysics Data System (ADS)

    Barbato, E.; Saveliev, A.; Voitsekhovitch, I.; Kirov, K.; Goniche, M.

    2014-12-01

    In this paper we report on simulations of lower hybrid current drive (LHCD) in JET closely comparing the simulation results to the available experimental data. The simulations are performed all over the relevant discharge duration by ASTRA. The LHCD module, FRTC, is based on a standard ray-tracing Fokker-Planck model. The purpose of the paper is to understand the present LHCD experiments issues within the limit of the LH linear propagation model. These issues are: (i) analysis of non-resonant collisional absorption (NRCA) of LH wave power in the main JET plasma during the current ramp-up phase and in steady-state (SS) scenarios, (ii) the lack of penetration of LHCD in high-density plasmas, (iii) current diffusion during the LHCD-assisted current ramp-up and (iv) assessment of the current profile alignment in JET SS discharges in the presence of LHCD. In recent experiments from FTU, JET and C_MOD, LHCD effects at high plasma density are either completely absent or less than expected. It has been shown, both in FTU and ALCATOR-C_MOD, that NRCA of LH wave power can be responsible for that. Indeed NRCA is estimated to be small in JET plasmas, at least in the main heating phase and therefore it is not expected to be responsible for the lack of penetration of LHW in high-density JET plasmas, however here we show for the first time that it can be effective during the early phase of the current ramp-up, when the plasma is still collisional. On the contrary it is suggested that the reduction of LHCD effects at high density may be attributed at least partially to the loss of accessibility of the n‖ spectrum effectively launched into the plasma. Furthermore it is shown that the linear propagation model provide very broad and stable LH current density profiles, with no need to include any non-linear spectral broadening. The current diffusion during the LHCD-assisted current ramp-up is investigated and a careful comparison between the simulated q-profiles and the measured

  13. Lower Hybrid Wave Induced SOL Emissivity Variation at High Density on the Alcator C-Mod Tokamak

    SciTech Connect

    Faust, I.; Terry, J. L.; Reinke, M. L.; Meneghini, O.; Shiraiwa, S.; Wallace, G. M.; Parker, R. R.; Schmidt, A. E.; Wilson, J. R.

    2011-12-23

    Lower Hybrid Current Drive (LHCD) in the Alcator C-Mod tokamak provides current profile control for the generation of Advanced Tokamak (AT) plasmas. Non-thermal electron bremsstrahlung emission decreases dramatically at n-bar{sub e}>1{center_dot}10{sup 20}[m{sup -3}] for diverted discharges, indicating low current drive efficiency. It is suggested that Scrape-Off-Layer (SOL) collisional absorption of LH waves is the cause for the absence of non-thermal electrons at high density. VUV and visible spectroscopy in the SOL provide direct information on collision excitation processes. Deuterium Balmer-, Lyman- and He-I transition emission measurements were used for initial characterization of SOL electron-neutral collisional absorption. Data from Helium and Deuterium LHCD discharges were characterized by an overall increase in the emissivity as well as an outward radial shift in the emissivity profile with increasing plasma density and applied LHCD power. High-temperature, high-field (T{sub e} = 5keV,B{sub t} = 8T) helium discharges at high density display increased non-thermal signatures as well as reduced SOL emissivity. Variations in emissivity due to LHCD were seen in SOL regions not magnetically connected to the LH Launcher, indicating global SOL effects due to LHCD.

  14. Spectral broadening of parametric instability in lower hybrid current drive at a high density

    NASA Astrophysics Data System (ADS)

    Cesario, R.; Amicucci, L.; Cardinali, A.; Castaldo, C.; Marinucci, M.; Napoli, F.; Paoletti, F.; De Arcangelis, D.; Ferrari, M.; Galli, A.; Gallo, G.; Pullara, E.; Schettini, G.; Tuccillo, A. A.

    2014-04-01

    The important goal of adding to the bootstrap current a more flexible tool, capable of producing and controlling steady-state profiles with a high fraction of non-inductive plasma current, could be reached using the lower hybrid current drive (LHCD) effect. Experiments performed on FTU (Frascati Tokamak Upgrade) demonstrated that LHCD can occur at reactor-graded high plasma density, provided that the parametric instability (PI)-produced broadening of the spectrum launched by the antenna is reduced under proper operating conditions, capable of producing relatively high temperature in the outer region of plasma column. This condition was produced by operations that reduce particle recycling from the vessel walls, and enhance the gas fuelling in the core by means of fast pellet. New results of FTU experiments are presented documenting that the useful effect of temperature at the periphery, which reduces the LH spectral broadening and enhances the LH-induced hard-x ray emission level, occurs in a broader range of plasma parameters than in previous work. Modelling results show that a further tool for helping LHCD at a high density would be provided by electron cyclotron resonant heating of plasma periphery. New information is provided on the modelling, able determining frequencies, growth rates and LH spectral broadening produced by PI, which allowed assessing the new method for enabling LHCD at high densities. Further robustness is provided to theoretical and experimental fundaments of the method for LHCD at a high density.

  15. Studies of challenge in lower hybrid current drive capability at high density regime in experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Li, M. H.; Li, Y. C.; Wang, M.; Liu, F. K.; Shan, J. F.; Li, J. G.; Wan, B. N.

    2017-02-01

    Aiming at a fusion reactor, two issues must be solved for the lower hybrid current drive (LHCD), namely good lower hybrid wave (LHW)-plasma coupling and effective current drive at high density. For this goal, efforts have been made to improve LHW-plasma coupling and current drive capability at high density in experimental advanced superconducting tokamak (EAST). LHW-plasma coupling is improved by means of local gas puffing and gas puffing from the electron side is taken as a routine way for EAST to operate with LHCD. Studies of high density experiments suggest that low recycling and high lower hybrid (LH) frequency are preferred for LHCD experiments at high density, consistent with previous results in other machines. With the combination of 2.45 GHz and 4.6 GHz LH waves, a repeatable high confinement mode plasma with maximum density up to 19~\\text{m}-3$ was obtained by LHCD in EAST. In addition, in the first stage of LHCD cyclic operation, an alternative candidate for more economical fusion reactors has been demonstrated in EAST and further work will be continued.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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 H98˜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.

  18. 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.

  19. Observation of Zero Current Density in the Core of JET Discharges with Lower Hybrid Heating and Current Drive

    NASA Astrophysics Data System (ADS)

    Hawkes, N. C.; Stratton, B. C.; Tala, T.; Challis, C. D.; Conway, G.; Deangelis, R.; Giroud, C.; Hobirk, J.; Joffrin, E.; Lomas, P.; Lotte, P.; Mailloux, J.; Mazon, D.; Rachlew, E.; Reyes-Cortes, S.; Solano, E.; Zastrow, K.-D.

    2001-09-01

    Simultaneous current ramping and application of lower hybrid heating and current drive (LHCD) have produced a region with zero current density within measurement errors in the core ( r/a<=0.2) of JET tokamak optimized shear discharges. The reduction of core current density is consistent with a simple physical explanation and numerical simulations of radial current diffusion including the effects of LHCD. However, the core current density is clamped at zero, indicating the existence of a physical mechanism which prevents it from becoming negative.

  20. Simulations of steady-state scenarios for Tore Supra using the CRONOS code

    NASA Astrophysics Data System (ADS)

    Basiuk, V.; Artaud, J. F.; Imbeaux, F.; Litaudon, X.; Bécoulet, A.; Eriksson, L.-G.; Hoang, G. T.; Huysmans, G.; Mazon, D.; Moreau, D.; Peysson, Y.

    2003-09-01

    Scenarios of steady-state, fully non-inductive current in Tore Supra are predicted using a package of simulation codes (CRONOS). The plasma equilibrium and transport are consistently calculated with the deposition of power. The achievement of high injected energy discharges up to 1 GJ is shown. Two main scenarios are considered: a low density regime with 90% non-inductive current driven by lower hybrid waves—lower hybrid current drive (LHCD)—and a high density regime combining LHCD and ion cyclotron resonance heating with a bootstrap current fraction up to 25%. The predictive simulations of existing discharges are also reported.

  1. Stabilization and Destabilization of Sawtooth Oscillations by Lower Hybrid Current Drive in the WT-3 Tokamak

    NASA Astrophysics Data System (ADS)

    Iida, Motomi; Maekawa, Takashi; Tanaka, Hitoshi; Ide, Shunsuke; Ogura, Kazuo; Hanada, Kazuaki; Iwamasa, Mikito; Itoh, Takehiko; Terumichi, Yasushi; Tanaka, Shigetoshi

    1988-11-01

    Sawtooth oscillations appearing in Ohmically heated (OH) plasmas are suppressed by the lower hybrid current drive (LHCD) in the WT-3 tokamak (R{=}65 cm, a{=}20 cm, Ip≃100 kA, \\bar{n}e{=}1-2× 1013 cm-3, qa≃4.5, and PLH≳100 kW). After the suppression, sawteeth reappear following m{=}1 oscillations in the LHCD plasmas. The latter sawteeth have a large amplitude and long period (Ts{=}2--5 msec), compared with the former one (Ts{=}0.5--1.5 msec). Furthermore, they do not accompany a precursor and crash very fast.

  2. 47 CFR 90.379 - ASTM E2213-03 DSRC Standard (ASTM-DSRC Standard).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Intelligent Transportation Systems Radio Service... for Telecommunications and Information Exchange Between Roadside and Vehicle Systems—5 GHz...

  3. Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics

    SciTech Connect

    Bak, J. G.; Lee, S. G.; Son, D.; Ga, E. M.

    2007-04-15

    An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.

  4. Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics

    NASA Astrophysics Data System (ADS)

    Bak, J. G.; Lee, S. G.; Son, D.; Ga, E. M.

    2007-04-01

    An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.

  5. Analog integrator for the Korea superconducting tokamak advanced research magnetic diagnostics.

    PubMed

    Bak, J G; Lee, S G; Son, D; Ga, E M

    2007-04-01

    An analog integrator, which automatically compensates an integrating drift, has been developed for the magnetic diagnostics in the Korea superconducting tokamak advanced research (KSTAR). The compensation of the drift is done by the analog to digital converter-register-digital to analog converter in the integrator. The integrator will be used in the equilibrium magnetic field measurements by using inductive magnetic sensors during a plasma discharge in the KSTAR machine. Two differential amplifiers are added to the signal path between each magnetic sensor and the integrator in order to improve the performance of the integrator because a long signal cable of 100 m will be used for the measurement in the KSTAR machine. In this work, the characteristics of the integrator with two differential amplifiers are experimentally investigated.

  6. Advances in long pulse operation at high radio frequency power in Tore Supra

    SciTech Connect

    Goniche, M.; Dumont, R.; Bourdelle, C.; Decker, J.; Delpech, L.; Ekedahl, A.; Guilhem, D.; Guimarães-Filho, Z.; Litaudon, X.; Lotte, Ph.; Maget, P.; Mazon, D.; Saoutic, B.

    2014-06-15

    The lower hybrid current drive (LHCD) system of Tore Supra has been upgraded for long pulse operation at higher power (7–8 MW). The two launchers have coupled on plasma 3.8 MW and 2.7 MW separately. This new power capability allows extending the operational domain of Tore Supra for long pulses at higher current and density. 38 long (20 s –155 s) discharges with very low loop voltage (V{sub L} = 30-60 mV) were performed with combined LHCD (5-5.7 MW) and ICRH (1–3 MW) powers, with up to 1 GJ of injected energy. Higher LHCD efficiency, with respect to the previous long discharges, is reported. MHD stability of these discharges is very sensitive to the LHCD power and parallel wave index, in particular in the preforming phase. For theses evanescent loop voltage plasmas, the ICRH power, in excess of 1 MW, is found to have a beneficial effect on the MHD stability.

  7. 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.

  8. The formation and evolution of extreme shear reversal in JET and its influence on local thermal transport

    NASA Astrophysics Data System (ADS)

    Hawkes, N. C.; Andrew, Y.; Challis, C. D.; DeAngelis, R.; Drozdov, V.; Hobirk, J.; Joffrin, E.; Lotte, P.; Mazon, D.; Rachlew, E.; Reyes-Cortes, S.; Sattin, F.; Solano, E.; Stratton, B. C.; Tala, T.; Valisa, M.; EFDA-JET workprogramme, contributors to the

    2002-07-01

    In JET discharges where lower hybrid heating and current drive (LHCD) is applied early during the current ramp, a region of the plasma with zero current density is formed near the axis. At the boundary of this region the current density is large and Bθ increases rapidly over a small distance. In the central region the safety factor, q, is effectively infinite, but this falls steeply in the boundary region. Outside the boundary region q reaches a minimum, where the magnetic shear s≡r/q (dq/dr) becomes zero. The formation of this region of zero current is dependent on both the heating and the current drive effects of the LHCD. When LHCD is switched off the current profile begins to relax towards the resistive peaked current distribution of fully inductive tokamak operation. If LHCD is not used in the current rise then these current profiles are not established. Although the physical mechanism exists to drive the central plasma current below zero, in most cases it appears to be prevented from going negative. At least one MHD mechanism has been identified which could be responsible for this. The presence of the zero central current is closely linked to the periodic relaxation events seen in these discharges. In these discharges, internal transport barriers have been observed with additional heating powers substantially below the values required to obtain barriers in monotonic q profile cases.

  9. Influence of gas puff location on the coupling of lower hybrid waves in JET ELMy H-mode plasmas

    SciTech Connect

    Ekedahl, A.; Petrzilka, V.; Baranov, Y.; Goniche, M.; Jacquet, P.; Klepper, C Christopher; Mailloux, J.

    2012-01-01

    Reliable coupling of the lower hybrid current drive (LHCD) to H-mode plasmas in JET is made feasible through a dedicated gas injection system, located at the outer wall and magnetically connected to the antenna (Pericoli Ridolfini et al 2004 Plasma Phys. Control. Fusion 46 349, Ekedahl et al 2005 Nucl. Fusion 45 351, Ekedahl et al 2009 Plasma Phys. Control. Fusion 51 044001). An experiment was carried out in JET in order to investigate whether a gas injection from the top of the torus, as is foreseen for the main gas injection in ITER, could also provide good coupling of the LH waves if magnetically connected to the antenna. The results show that a top gas injection was not efficient for providing a reliable LHCD power injection, in spite of being magnetically connected and in spite of using almost twice the amount of gas flow compared with the dedicated outer mid-plane gas puffing system. A dedicated gas injection system, set in the outer wall and magnetically connected to the LHCD antenna, is therefore recommended in order to provide the reliable coupling conditions for an LHCD antenna in ITER.

  10. 78 FR 28217 - Sunshine Act Meeting: FCC To Hold Open Commission Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-14

    ... COMMUNICATIONS & and Encouraging OFFICE OF Innovation through ENGINEERING & Establishment of an TECHNOLOGY. Air-Ground Mobile Broadband Secondary Service for Passengers Aboard Aircraft in the 14.0- 14.5 GHz Band (RM... Air-Ground Mobile Broadband secondary service in the 14.0- 14.5 GHz band, while ensuring that...

  11. 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

    ... the 10.7-14.5 GHz bands. The technical information shall demonstrate that the proposed NGSO FSS system... Service (NGSO FSS) system in the 10.7-14.5 GHz bands. The technical information shall demonstrate that the... may request at any time additional information from the NGSO FSS system applicant or licensee...

  12. Supersonic Molecular Beam Injection Effects on Tokamak Plasma Applied Non-axisymmetric Magnetic Perturbation

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; in, Y.; Jeon, Y. M.; Hahn, S. H.; Lee, K. D.; Nam, Y. U.; Yoon, S. W.

    2016-10-01

    In KSTAR experiments, the change of tokamak plasma behavior by supersonic molecular beam injection (SMBI) was investigated by applying resonant magnetic perturbations(RMP) that could suppress edge localized modes (ELMs). When the SMBI is applied, the symptom representing ELM suppression by RMP is disappeared. The SMBI acts as a cold pulse on the plasma keeping the total confinement engergy constant. However, it makes plasma density increase and change the plasama collisionality which can play a role in the edge-pedestal build-up processing. This work was supported by Project PG1201-2 and the KSTAR research project funded by Korea Ministry of Science, ICT and Future Planning.

  13. 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.

  14. Advances in lower hybrid current drive technology on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Wallace, G. M.; Shiraiwa, S.; Hillairet, J.; Preynas, M.; Beck, W.; Casey, J. A.; Doody, J.; Faust, I. C.; Fitzgerald, E.; Johnson, D. K.; Kanojia, A. D.; Koert, P.; Lau, C.; Lin, Y.; Leccacorvi, R.; MacGibbon, P.; Meneghini, O.; Murray, R.; Parker, R. R.; Terry, D. R.; Vieira, R.; Wilson, J. R.; Wukitch, S.; Zhou, L.

    2013-07-01

    Lower hybrid current drive (LHCD) is an attractive option for non-inductive tokamak operation due to its high current drive efficiency and ability to drive current off axis. The parameters of the Alcator C-Mod LHCD system (f0 = 4.6 GHz, Bφ ≃ 5.5 T, \\bar{n}_\\rme \\simeq 10^{20}\\,m^{-3} ) are similar to the proposed LHCD system on ITER. This paper will describe improvements in LHCD technology on C-Mod designed to increase single-pass absorption at high \\bar{n}_\\rme , extend pulse length (to >3 s), and increase power delivered to the plasma (to ∼2 MW). Modelling of lower hybrid (LH) wave propagation indicates that the observed loss of LHCD efficiency at higher \\bar{n}_\\rme can be mitigated by enhancing the single pass power absorption through use of an off mid-plane launcher. The four rows of the launcher are located above the mid-plane (with Ip and Bφ both clockwise viewing from the top down) in order to exploit the poloidal upshift of n‖ as rays propagate from the antenna into the plasma. The transmitter protection system (TPS) was redesigned to model the coolant temperature in real time and shut off the klystron beam voltage if the coolant is close to boiling. The TPS upgrade has been installed and operated on C-Mod for pulses up to 4.5 s into dummy loads and 1.0 s into the plasma. A new movable local LH launcher protection limiter was designed to reduce reflection coefficients across a wide range of launcher positions. Finally, a high power waveguide double-stub tuner is under development to provide feedback controlled load matching to reduce power reflected from the antenna under poor coupling conditions.

  15. 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.

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

    DOE PAGES

    Orlov, D. M.; Evans, T. E.; Moyer, R. A.; ...

    2016-06-03

    Here, 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-resonantmore » 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. 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.« less

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

    SciTech Connect

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

    2016-06-03

    Here, 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. 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.

  18. 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.

  19. 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).

  20. 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.

  1. Equilibria and Stability of JET Current Hole Discharges

    NASA Astrophysics Data System (ADS)

    Stratton, B. C.; Hawkes, N. C.; Breslau, J.; Reyes-Cortes, S.; Jardin, S.; Park, W.; Zakharov, L.

    2002-11-01

    Injection of Lower Hybrid Heating and Current Drive (LHCD) into the current ramp-up phase of JET discharges has produced extremely reversed q-profiles characterized by a core region of near zero current density (within Motional Stark Effect diagnostic measurement errors). Non-inductive, off-axis co-current drive induces a back electromotive force inside the non-inductive current radius that drives a negative current in the plasma core. The core current density does not go negative, although current diffusion calculations indicate that there is sufficient LHCD to cause this. A possible explanation of the observed core current density clamping near zero is that MHD instabilities redistribute the core current soon after it goes negative. This is seen in nonlinear resistive MHD simulations in toroidal geometry which predict that these discharges undergo n=0 reconnection events which clamp the core current near zero.

  2. Study of Inverted Sawtooth Activities in EAST Plasma

    NASA Astrophysics Data System (ADS)

    Chen, Yebin; Hu, Liqun; Chen, Kaiyun; Li, Miaohui

    2014-03-01

    On the EAST tokamak, during whole off-axis LHCD (low hybrid current drive) limiter discharge, inverted sawteeth oscillations on the SXR (soft X-ray camera) signals appear continuously, and no positive sawtooth is observed. It is thought that this phenomenon is caused by the curvature pinch, though it could partly be explained by the electron temperature profile observed on the PHA (soft X-ray pulse height analyzer) system. The off-axis LHCD and Ohmic heating generate a non-monotonic q profile. According to the curvature pinch effect, this q profile leads to a special electron density profile that has a valley ring. The non-monotonic q profile and the special electron density profile lead to this interesting phenomenon.

  3. 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)

  4. Synergy between LH and ECH waves in the FTU tokamak

    NASA Astrophysics Data System (ADS)

    Ridolfini, V. Pericoli; Barbato, E.; Bruschi, A.; Dumont, R.; Gandini, F.; Giruzzi, G.; Gormezano, C.; Granucci, G.; Panaccione, L.; Peysson, Y.; Podda, S.; Saveliev, A. N.

    2001-10-01

    Experiments on the effects of simultaneous injection of LH and ECH power have been carried out in FTU, with up to PLH=1 MW and PECH=0.75 MW. In the absence of the cold ECH resonance in the plasma, the ECH power is absorbed on the suprathermal electron tail sustained by LHCD, as predicted theoretically, and causes the central electron temperature Te0 to increase up to 1.2 keV. With the cold resonance at the center, in a sawteeth and MHD free plasma, almost fully sustained by LHCD, a quasi-stationary electron transport barrier is built-up in a region r/a<0.5. Te0 rises by more than 4 keV, for only 0.35 MW of ECH power.

  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. Observation of Self-Generated Flows in Tokamak Plasmas with Lower-Hybrid-Driven Current

    SciTech Connect

    Ince-Cushman, A.; Rice, J. E.; Reinke, M.; Greenwald, M.; Wallace, G.; Parker, R.; Fiore, C.; Hughes, J. W.; Bonoli, P.; Shiraiwa, S.; Hubbard, A.; Wolfe, S.; Hutchinson, I. H.; Marmar, E.; Bitter, M.; Wilson, J.; Hill, K.

    2009-01-23

    In Alcator C-Mod discharges lower hybrid waves have been shown to induce a countercurrent change in toroidal rotation of up to 60 km/s in the central region of the plasma (r/a{approx}<0.4). This modification of the toroidal rotation profile develops on a time scale comparable to the current redistribution time ({approx}100 ms) but longer than the energy and momentum confinement times ({approx}20 ms). A comparison of the co- and countercurrent injected waves indicates that current drive (as opposed to heating) is responsible for the rotation profile modifications. Furthermore, the changes in central rotation velocity induced by lower hybrid current drive (LHCD) are well correlated with changes in normalized internal inductance. The application of LHCD has been shown to generate sheared rotation profiles and a negative increment in the radial electric field profile consistent with a fast electron pinch.

  7. Experimental exploration of profile control in the Princeton Beta Experiment-Modified (PBX-M) tokamak

    SciTech Connect

    Bernabei, S.; Bell, R.; Chance, M.; Chu, T.K.; Corneliussen, M.; Davis, W.; Gettelfinger, G.; Gibney, T.; Greenough, N.; Hatcher, R.; Hermann, H.; Ignat, D.; Jardin, S.; Kaita, R.; Kaye, S.; Kessel, C.; Kozub, T.; Hugel, H.; Lagin, L.; LeBlanc, B.; Manickam, J.; Okabayashi, M.; Oliver, H.; Ono, M.; Paul, S.; Preische, S.; Roney, P.; Sauthoff, N.; Schweitzer, S.; Sesnic, S.; Sun, Y.; Takahashi, H.; Tighe, W.; Valeo, E.; von Goeler, S.; Voss, K.; Mauel, M.; Navratil, G.; Cesario, R.; Batha, S.; Levinton, F.; Rimini, F.; Asakura, N.; Jones, S.; Kesner, J.; Luckhardt, S.; Paoletti, F.; Woskov, P.; Zolfaghari, A.; Seki, T.; Bell, J.; Dunlap, J.; England, A.; Greenwood, D.; Harris, J.; Henkel, G.; Hirshman, S.; Isler, R.; Lee, D.; Blush, L.; Conn, R.; Doerner, R.; Hirooka, Y.; Lehmer, R.; Schmitz, L.; Tynan, G.

    1993-05-01

    The experimental program of the Princeton Beta Experiment-Modified (PBX-M) Tokamak is directed towards tailoring plasma profiles to achieve greater stability and confinement and to gain access to the second stability region. Modification of the current density profile has been achieved with lower hybrid current drive (LHCD), leading to a regime free of global magnetohydrodynamic modes, while raising the value of q(O) above unity. The diffusion of the fast electrons produced by LHCD has been examined using two dimensional hard x-ray imaging. Ion Bernstein waves (IBW) have been used for ion heating: a preliminary analysis shows that ion heating was spatially localized and in agreement with theoretical calculations. Divertor biasing has modified the electric field inside the last closed surface, resulting in the formation of a transport barrier, which in turn has reduced the threshold power of Neutral Beam Injection (NBI) for H-mode transition by 25%.

  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. 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.

  10. 47 CFR 0.408 - OMB control numbers and expiration dates assigned pursuant to the Paperwork Reduction Act of 1995.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Band Segmentation Plan Amending the Commission's Rules to Redesignate the 27.5—29.5 GHz Frequency Band... Policies Concerning Attribution of Joint Sales Agreements in Local Television Markets, NPRM, MB Docket No...

  11. A stationary long-pulse ELM-absent H-mode regime in EAST

    NASA Astrophysics Data System (ADS)

    Ye, Y.; Xu, G. S.; Wan, B. N.; Chen, R.; Yan, N.; Guo, H. Y.; Shao, L. M.; Yang, Q. Q.; Wang, H. Q.; Zhang, W.; Xia, T. Y.; Zhang, T.; Li, Y. Y.; Wang, T. F.; Zang, Q.; Hu, Y. J.; Wu, G. J.; Zhang, L.; Hao, B. L.; Wang, L.; Li, Y. L.; Wu, X. Q.; Chen, L.; Lan, H.; Wang, Y. F.; Xu, J. C.; Hu, G. H.; Ding, S. Y.; Zhang, H.; Zhao, N.; Li, J.; The EAST Team

    2017-08-01

    A stationary edge-localized mode (ELM)-absent H-mode regime, with an electrostatic edge coherent mode (ECM) which resides in the pedestal region, has been achieved in the EAST tokamak recently. This regime allows the operation of a nearly fully noninductive long pulse (>15 s), exhibiting a relatively high pedestal and good global energy confinement with {{H}98,y2} near 1.2, and excellent impurity control. Furthermore, this regime is mostly obtained with a 4.6 GHz lower hybrid current drive (LHCD) or counter-current neutral beam injection (NBI), plus electron cyclotron resonance heating, and an extensive lithium wall coating. This stationary ELM-absent H-mode regime transits to a stationary small ELM H-mode regime, and upon additional heating power from the 2.45 GHz LHCD, an ion cyclotron resonant frequency or co-current NBI is applied (under 4.6 GHz LHCD heating background). A slight change of the plasma configuration also makes the small ELMs reappear. The experimental observations suggest that a long-pulse ELM-absent regime can be induced by the ECM, which exhibits strong electrostatic fluctuations and may provide a channel for continuous particle (especially impurities) and heat exhaust across the pedestal. The ECM exists in the collisionality of ν e*   =  2.5-4 and the pressure gradient |\

  12. Lower hybrid current drive experiments with different launched wave frequencies in the EAST tokamak

    NASA Astrophysics Data System (ADS)

    Li, M. H.; Ding, B. J.; Liu, F. K.; Shan, J. F.; Wang, M.; Xu, H. D.; Liu, L.; Hu, H. C.; Zhang, X. J.; Li, Y. C.; Wei, W.; Wu, Z. G.; Ma, W. D.; Yang, Y.; Feng, J. Q.; Jia, H.; Wang, X. J.; Wu, D. J.; Chen, M.; Xu, L.; Wang, J.; Lin, S. Y.; Zhang, J. Z.; Qian, J. P.; Luo, Z. P.; Zang, Q.; Han, X. F.; Zhao, H. L.; Peysson, Y.; Decker, J.; Ekedahl, A.; Hillairet, J.; Goniche, M.

    2016-10-01

    EAST has been equipped with two high power lower hybrid current drive (LHCD) systems with operating frequencies of 2.45 GHz and 4.6 GHz. Comparative LHCD experiments with the two different frequencies were performed in the same conditions of plasma for the first time. It was found that current drive (CD) efficiency and plasma heating effect are much better for 4.6 GHz LH waves than for the one with 2.45 GHz. High confinement mode (H-mode) discharges with 4.6 GHz LHCD as the sole auxiliary heating source have been obtained in EAST and the confinement is higher with respect to that produced previously by 2.45 GHz. A combination of ray-tracing and Fokker-Planck calculations by using the C3PO/LUKE codes was performed in order to explain the different experimental observations between the two waves. In addition, the frequency spectral broadening of the two LH wave operating frequencies was surveyed by using a radio frequency probe.

  13. 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 ^}.

  14. 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 .

  15. Hard x-ray diagnostic for lower hybrid experiments on Alcator C-Mod

    SciTech Connect

    Liptac, J.; Parker, R.; Tang, V.; Peysson, Y.; Decker, J.

    2006-10-15

    Alcator C-Mod's lower hybrid current drive (LHCD) system allows the exploration of advanced tokamak (AT) regimes at densities relevant to ITER and fusion reactors. The location of the LHCD is critical to AT performance and may be inferred by measuring the nonthermal bremsstrahlung emission in the hard x-ray (HXR) region. A pinhole camera using an array of 32 CdZnTe detectors is used to image energies in the 20-200 keV range. Detectors and pulse processing electronics are integrated into a compact and modular package making extensive use of printed circuit board and surface mount technology. The system also makes use of fast digitization and software signal processing techniques. An ambient environment of neutrons, gammas, and high rf power requires careful shielding. Shielding is studied using the neutron and photon transport code MCNP. The design of the diagnostic is presented along with background measurements in lieu of LHCD fast electrons. Background measurements are then compared to advanced modeling results to predict the power threshold for meaningful HXR data for a H-mode target plasma.

  16. Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

    NASA Astrophysics Data System (ADS)

    Gao, Q. D.; Budny, R. V.

    2015-03-01

    By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (Ti,e) and toroidal velocity (Vϕ) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LH driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition.

  17. Experimental investigations of LHW-plasma coupling and current drive related to achieving H-mode plasmas in EAST

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Kong, E. H.; Li, M. H.; Zhang, Lei; Wei, W.; Wang, M.; Xu, H. D.; Li, Y. C.; Ling, B. L.; Zang, Q.; Xu, G. S.; Han, X. F.; Zhao, H. L.; Zhang, Ling; Zhao, L. M.; Hu, H. C.; Yang, Y.; Liu, L.; Ekedahl, A.; Goniche, M.; Cesario, R.; Peysson, Y.; Decker, J.; Basiuk, V.; Huynh, P.; Artaud, J.; Imbeaux, F.; Shan, J. F.; Liu, F. K.; Zhao, Y. P.; Gong, X. Z.; Hu, L. Q.; Gao, X.; Guo, H. Y.; Wan, B. N.; Li, J. G.; the EAST Team

    2013-11-01

    Aimed at high-confinement (H-mode) plasmas in the Experimental Advanced Superconducting Tokamak (EAST), the effect of local gas puffing from electron and ion sides of a lower hybrid wave (LHW) antenna on LHW-plasma coupling and high-density experiments with lower hybrid current drive (LHCD) are investigated in EAST. Experimental results show that gas puffing from the electron side is more favourable to improve coupling compared with gas puffing from the ion side. Investigations indicate that LHW-plasma coupling without gas puffing is affected by the density near the LHW grill (grill density), hence leading to multi-transition of low-high-low (L-H-L) confinement, with a correspondingly periodic characteristic behaviour in the plasma radiation. High-density experiments with LHCD suggest that strong lithiation gives a significant improvement on current drive efficiency in the higher density region than 2 × 1019 m-3. Studies indicate that the sharp decrease in current drive efficiency is mainly correlated with parametric decay instability. Using lithium coating and gas puffing from the electron side of the LHW antenna, an H-mode plasma is obtained by LHCD in a wide range of parameters, whether LHW is deposited inside the half-minor radius or not, implying that a central and large driven current is not a necessary condition for the H-mode plasma. H-mode is investigated with CRONOS.

  18. Analysis of the efficiency of lower hybrid current drive in the FT-2 tokamak

    SciTech Connect

    Lashkul, S. I.; Altukhov, A. B.; Gurchenko, A. D.; D'yachenko, V. V.; Esipov, L. A.; Kantor, M. Yu.; Kuprienko, D. V.; Irzak, M. A.; Savel'ev, A. N.; Sidorov, A. V.; Stepanov, A. Yu.; Shatalin, S. V.

    2010-09-15

    Results are presented from experimental studies of the efficiency of lower hybrid current drive (LHCD) in the FT-2 tokamak. The dependence of the LHCD efficiency on the grill phasing {Delta}{phi} and RF oscillator power was determined experimentally in a wide range of plasma densities. It is shown that, at high plasma currents (i.e., at sufficiently high electron temperatures), current drive is suppressed when the plasma density reaches its resonance value n{sub LH} for the pumping wave frequency, rather than when parametric decay comes into play (as was observed in regimes with lower plasma currents and, accordingly, lower electron temperatures T{sub e}). In order to analyze the experimentally observed effect of LHCD and its dependence on the value and sign of the antenna phasing, the spectra of the excited LH waves, P(N{sub z}), were calculated. Simulations using the FRTC code with allowance for the P(N{sub z}) spectrum and the measured plasma parameters made it possible to calculate the value and direction of the LH-driven current, which are determined by the spectrum of the excited LH waves. It is shown that the synergetic effect caused by the interaction between different spectral components of the excited RF wave plays a decisive role in the bridging of the gap in the wave spectrum.

  19. RF heating and current drive experiment on JT-60

    NASA Astrophysics Data System (ADS)

    1987-09-01

    Recent experimental results of Lower Hybrid and Ion Cyclotron Range of Frequencies (LHRF and ICRF) heating and current drive are presented on JT-60 at JAERI. Three LHRF at 2 GHz and one ICRF at 120 MHz system are installed in JT-60. Each unit has launched 2.1-2.4 MW of RF power into the JT-60, so far. Steady current up to 2 MA for 2.5 sec have been maintained only by LHCD at a density of ne=0.32×1019 m-3 with 3.1 MW. The current drive efficiency defined by ɛCD=ne (1019 m-3)R(m)IRF(MA)/PLH(MW) reach 1.5-3.0 by combination of LHCD and NBI heating. High central electron heating up to 6 keV is demonstrated at the density ne=1.7×10-19 m-3. Current profile control and improvement of energy confinement time via LHCD is observed with and without NBI heating. Optimization of the second harmonic ICRF heating is studied with 2×2 phased loop antenna. In combination heating of ICRF and NBI, remarkable beam acceleration is observed in the plasma core.

  20. Improved confinement mode induced by a MARFE during lower hybrid current drive in the HT-7 tokamak

    NASA Astrophysics Data System (ADS)

    Asif, M.; Gao, X.; HT-7 Team

    2006-04-01

    Lower hybrid current drive (LHCD) experiments have been carried out to achieve high performance for long pulse operation in the Hefei tokamak-7 (HT-7) superconducting tokamak. Multifaceted asymmetric radiation from the edge (MARFE) phenomena and an improved confinement mode induced by a MARFE are observed in LHCD plasmas when PLH>160 kW and the edge safety factor q(a) is slightly less than 6.5. It is found that an improved confinement mode induced by a MARFE, characterized by Hα line emissions drops and the line-averaged density increase is triggered in the MARFE discharges. The MARFE event occurs at t=1120 ms following the L H transition, and the improved confinement phase exists for about 65 ms from t=1140 ms after the L H transition. The LHCD plasma results basically are typical with MARFEs and it is an improved confinement mode; they are unique in that they appear at very low \\bar {n}_e values in the HT -7 tokamak.

  1. Intrinsic torque reversals induced by magnetic shear effects on the turbulence spectrum in tokamak plasmasa)

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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 ̂ ) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak s ̂ . Based on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak s ̂ discharges and that the value of s ̂ c r i t is consistent with the experimental results ŝ c r i t e x p ≈ 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 ̂ 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 ̂ .

  2. Hard x-ray diagnostic for lower hybrid experiments on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Liptac, J.; Parker, R.; Tang, V.; Peysson, Y.; Decker, J.

    2006-10-01

    Alcator C-Mod's lower hybrid current drive (LHCD) system allows the exploration of advanced tokamak (AT) regimes at densities relevant to ITER and fusion reactors. The location of the LHCD is critical to AT performance and may be inferred by measuring the nonthermal bremsstrahlung emission in the hard x-ray (HXR) region. A pinhole camera using an array of 32 CdZnTe detectors is used to image energies in the 20-200keV range. Detectors and pulse processing electronics are integrated into a compact and modular package making extensive use of printed circuit board and surface mount technology. The system also makes use of fast digitization and software signal processing techniques. An ambient environment of neutrons, gammas, and high rf power requires careful shielding. Shielding is studied using the neutron and photon transport code MCNP. The design of the diagnostic is presented along with background measurements in lieu of LHCD fast electrons. Background measurements are then compared to advanced modeling results to predict the power threshold for meaningful HXR data for a H-mode target plasma.

  3. Absorption of lower hybrid waves in the scrape off layer of a diverted tokamak

    SciTech Connect

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

    2010-08-15

    The goal of the Lower Hybrid Current Drive (LHCD) system on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] is to investigate current profile control under plasma conditions relevant to future tokamak experiments. Experimental observations of a LHCD ''density limit'' for C-Mod are presented in this paper. Bremsstrahlung emission from relativistic fast electrons in the core plasma drops suddenly above line averaged densities of 10{sup 20} m{sup -3} ({omega}/{omega}{sub LH{approx}}3-4), well below the density limit previously observed on other experiments ({omega}/{omega}{sub LH{approx}}2). Electric currents flowing through the scrape off layer (SOL) between the inner and outer divertors increase dramatically across the same density range that the core bremsstrahlung emission drops precipitously. These experimental x-ray data are compared to both conventional modeling, which gives poor agreement with experiment above the density limit and a model including collisional absorption in the SOL, which dramatically improves agreement with experiment above the observed density limit. These results show that strong absorption of LH waves in the SOL is possible on a high density tokamak and the SOL must be included in simulations of LHCD at high density.

  4. Design, and initial experiment results of a novel LH launcher on Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Shiraiwa, S.; Meneghini, O.; Parker, R. R.; Wallace, G.; Wilson, J.; Faust, I.; Lau, C.; Mumgaard, R.; Scott, S.; Wukitch, S.; Beck, W.; Doody, J.; Irby, J.; MacGibbon, P.; Johnson, D.; Kanojia, A.; Koert, P.; Terry, D.; Vieira, R.; Alcator C-Mod Team

    2011-10-01

    The design, construction and initial results of a new lower hybrid current drive (LHCD) launcher on Alcator C-Mod (Hutchinson et al 1994 Phys. Plasmas 1 1511) are presented. The new LHCD launcher (LH2) is based on a novel splitter concept which evenly distributes the microwave power in four ways in the poloidal direction. This design allows for simplification of the feeding structure while keeping the flexibility to vary the peak launched toroidal index of refraction, Ntoroidal, from -3.8 to 3.8. An integrated model predicts good plasma coupling over a wide range of edge densities, while poloidal variations of the edge density are found to affect the evenness of power splitting in the poloidal direction. The measured transmission loss is about 30% lower than the previous launcher, and a clean Ntoroidal spectrum has been confirmed. Power handling capability exceeding an empirical weak conditioning limit and reliable operation up to 1.1 MW net LHCD power have been achieved. A survey of antenna-plasma coupling shows the existence of a millimetric vacuum gap in front of the launcher. Fully non-inductive, reversed shear plasma operation has been demonstrated and sustained for multiple current diffusion times. The current drive efficiency, ηLH ≡ neR0Ip/PLH, of these plasmas is (0.2-0.25) × 1020 m-2A W-1, which is in agreement with the expected efficiency on the International Thermonuclear Experimental Reactor (ITER).

  5. Radio upper limits on DLT17ch from the ATCA

    NASA Astrophysics Data System (ADS)

    Bannister, Keith; Corsi, Alessandra; Sand, David

    2017-08-01

    We observed the type-Ib/c supernova DLT17ch (=SN 2017 gax; ATel #10638) for approximately 8 hrs with the Australia Telescope Compact Array starting on 2017-08-20 19:34 UTC. The array was in the EW352 configuration which has a resolution of around 30" at 5.5 GHz. Imaging at 5.5 GHz was somewhat hampered by the presence of strong continuum emission from the host galaxy.

  6. 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).

  7. On estimators of the jet bolometric luminosity of Fermi 2LAC blazars

    NASA Astrophysics Data System (ADS)

    Wang, Zerui; Xue, Rui; Du, Leiming; Xie, Zhaohua; Xiong, Dingrong; Yi, Tingfeng; Xu, Yunbing; Liu, Wenguang

    2017-10-01

    Bolometric luminosity is a basic physical parameter that is widely used in the study of blazars. Due to the lack of simultaneous full wavelength data, several estimators of the bolometric luminosity are being used in practice. In this paper, we study and evaluate the reliability and significance of six estimators, the 5GHz luminosity, the 1keV luminosity, the γ-ray luminosity, the 5GHz luminosity + the 1keV luminosity, the 5GHz luminosity + the γ-ray luminosity and the 1keV luminosity + the γ-ray luminosity, by analyzing the linear correlations between the integrated bolometric luminosity and them. Our main results are as follows. (i) All the six estimators are reliable in the sense that they are all significant correlated with the bolometric luminosity. (ii) Ranking from the higher significance of the reliability to lower one the six estimators are the 5GHz luminosity + the γ-ray luminosity, the 1keV luminosity + the γ-ray luminosity, γ-ray luminosity, the 5GHz luminosity + the 1keV luminosity, the 5GHz luminosity and the 1keV luminosity. (iii) We suggest that the bolometric luminosity can be well estimated by the γ-ray luminosity using the best linear equation that given in this paper for Fermi FSRQs. (iv) According to the linear regressions obtained in the analysis, we provide calibration for each estimator.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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 (Te_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 (Te_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, f0=144 GHz), an increase of Te in the outer plasma (from 40 eV to 80 eV at r/a˜0.8) is expected by the JETTO code

  9. 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

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

    SciTech Connect

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

    2016-04-15

    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{sup −1}. The upper limit corresponds to the normalized wavenumber k{sub θ}ρ{sub e} 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.

  11. 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.

  12. The Effect of a Gap Nonlinearity on Recursive Parameter Identification Algorithms

    DTIC Science & Technology

    1988-05-09

    returns to equilibrium before touchdown on the other side. In retrospect, working with difference equations directly might be preferable. The displacement...2.2.2). KSTAR (2.2,2) REA KBAR(2).KAST(2) DOUBLEPRECISION DEN OPEN CUNIT=29 ,STATUS= ’OLD’) OPEN (UNIT=25 ,STATUS=’ OLD’) OPEN (UN IT=26.STATUS= ’NEW...OPEN (UN IT=27 .STATUS= ’NEW’) OPEN (UN IT=52, STATUS=’ OLD’) C DO 30 12=1,2 DO 20 I=1,2 DO 10 J=1.2 KSTAR (12.I.J)=0 P(12,I.J)=0 PSTAR(12.I,J)=O S1(I.J

  13. 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.

  14. Series of powerful CW gyrotrons in the range 105 - 140 GHz

    NASA Astrophysics Data System (ADS)

    Denisov, Gregory; Kazansky, Igor; Malygin, Vladimir; Soluyanova, Elena; Tai, Evgeny; Chirkov, Aleksey

    2017-07-01

    GYCOM in collaboration with Institute of Applied Physics (IAP) designed, fabricated and tested two different gyrotrons with similar to ITER parameters at 105 - 140 GHz frequency range. Set of gyrotron system beside the tube includes matching optic unit (MOU) and elements of evacuated transmission lines. One gyrotron system was installed and operates at plasma machines EAST / ASIPP / China, another system is delivered to KSTAR / NFRI / Korea.

  15. Experimental observations and modelling of intrinsic rotation reversals in tokamaks

    NASA Astrophysics Data System (ADS)

    Camenen, Y.; Angioni, C.; Bortolon, A.; Duval, B. P.; Fable, E.; Hornsby, W. A.; McDermott, R. M.; Na, D. H.; Na, Y.-S.; Peeters, A. G.; Rice, J. E.

    2017-03-01

    The progress made in understanding spontaneous toroidal rotation reversals in tokamaks is reviewed and current ideas to solve this ten-year-old puzzle are explored. The paper includes a summarial synthesis of the experimental observations in AUG, C-Mod, KSTAR, MAST and TCV tokamaks, reasons why turbulent momentum transport is thought to be responsible for the reversals, a review of the theory of turbulent momentum transport and suggestions for future investigations.

  16. A Comparison of the Aging Kinetics of a Cast Alumina-6061 Aluminum Composite and a Monolithic 6061 Aluminum Alloy

    DTIC Science & Technology

    1989-12-01

    PERFORM RESISTIVITY CALCULATION 49 APPENDIX E. PROGRAM TO CALCULATE KSTAR .. ........ 50 APPENDIX F. PROGRAM TO CALCUATE THERMODYNAMIC QUANTITIES...potential nucleation sites and permit the precipitate to form. The structure, still a supersaturated solid solution, not at equilibrium 2 and therefore...precipitate forms and grows. If the alloy is held at the aging temperature for a sufficient time, an equilibrium structure of primary solid solution

  17. Computer Program for Calculation of Separated Turbulent Flows on Axisymmetric Afterbodies

    DTIC Science & Technology

    1977-06-01

    FOR BOUNDARY LAYER/INVISCID FLOW EQUILIBRIUM CONVERGED This message is printed whenever the maximum change in 6* between iterations is less than...0 0 [ + 0 ~ 0 0 5 7 4 E + 0 1 0 o 8 4 0 ~ + 0 0 0 * 5 8 1 E ~ 0 2 O , 1 9 I E t 0 2 GAM AM|NF KSTAR PSTAH ~PSTAR CP3 46 O e 8 9 3 5 E # O 0

  18. 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.

  19. 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.

  20. Diamagnetic loop measurement in Korea Superconducting Tokamak Advanced Research machine.

    PubMed

    Bak, J G; Lee, S G; Kim, H S

    2011-06-01

    Diamagnetic loop (DL), which consists of two poloidal loops inside the vacuum vessel, is used to measure the diamagnetic flux during a plasma discharge in the Korea Superconducting Tokamak Advanced Research (KSTAR) machine. The vacuum fluxes in the DL signal can be compensated up to 0.1 mWb by using the coefficients, which are obtained from experimental investigations, in the vacuum flux measurements during vacuum shots under same operational conditions of magnetic coils for plasma experiment in the KSTAR machine. The maximum error in the diamagnetic flux measurement due to the errors of the coefficients was estimated as ∼0.22 mWb. From the diamagnetic flux measurements for the ohmically heated circular plasmas in the KSTAR machine, the stored energy agrees well with the estimated kinetic energy within the discrepancy of 25%. When the electron cyclotron heating, the neutral beam injection, and the ion cyclotron resonance heating are added to the ohmically heated limiter plasmas, the additional heating effects can be clearly observed from the increase of the stored energy evaluated in the DL measurement.

  1. Diamagnetic loop measurement in Korea Superconducting Tokamak Advanced Research machine

    SciTech Connect

    Bak, J. G.; Lee, S. G.; Kim, H. S.

    2011-06-15

    Diamagnetic loop (DL), which consists of two poloidal loops inside the vacuum vessel, is used to measure the diamagnetic flux during a plasma discharge in the Korea Superconducting Tokamak Advanced Research (KSTAR) machine. The vacuum fluxes in the DL signal can be compensated up to 0.1 mWb by using the coefficients, which are obtained from experimental investigations, in the vacuum flux measurements during vacuum shots under same operational conditions of magnetic coils for plasma experiment in the KSTAR machine. The maximum error in the diamagnetic flux measurement due to the errors of the coefficients was estimated as {approx}0.22 mWb. From the diamagnetic flux measurements for the ohmically heated circular plasmas in the KSTAR machine, the stored energy agrees well with the estimated kinetic energy within the discrepancy of 25%. When the electron cyclotron heating, the neutral beam injection, and the ion cyclotron resonance heating are added to the ohmically heated limiter plasmas, the additional heating effects can be clearly observed from the increase of the stored energy evaluated in the DL measurement.

  2. 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.

  3. A High-Resolution Radio Continuum Study Of The Dwarf Irregular Galaxy IC 10

    NASA Astrophysics Data System (ADS)

    Westcott, J.; Brinks, E.; Beswick, R. J.; Heesen, V.; Argo, M. K.; Baldi, R. D.; Fenech, D. M.; McHardy, I. M.; Smith, D. J. B.; Williams, D. R. A.

    2017-01-01

    We present high-resolution e-MERLIN radio continuum maps of the Dwarf Irregular galaxy IC 10 at 1.5 GHz and 5 GHz. We detect 11 compact sources at 1.5 GHz, 5 of which have complementary detections at 5 GHz. We classify 3 extended sources as compact HII regions within IC 10, 5 sources as contaminating background galaxies and identify 3 sources which require additional observations to classify. We do not expect that any of these 3 sources are Supernova Remnants as they will likely be resolved out at the assumed distance of IC 10 (0.7 Mpc). We correct integrated flux densities of IC 10 from the literature for contamination by unrelated background sources and obtain updated flux density measurements of 354 ± 11 mJy at 1.5 GHz and 199 ± 9 mJy at 4.85 GHz. The background contamination does not contribute significantly to the overall radio emission from IC 10, so previous analysis concerning its integrated radio properties remain valid.

  4. 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.

  5. Chapter 3: Internal Transport Barrier Studies in the FTU

    SciTech Connect

    Barbato, E.; Pericoli-Ridolfini, V.; Castaldo, C.; Esposito, B.; Giovannozzi, E.; Gormezano, C.; Granucci, G.; Leigheb, M.; Marinucci, M.; Mirizzi, F.; Panaccione, L.; Podda, S.; Romanelli, M.; Smeulders, P.; Sozzi, C.

    2004-05-15

    Strong electron internal transport barriers (ITBs) are obtained in the Frascati Tokamak Upgrade (FTU) with the combined injection of lower hybrid (LH) (up to 1.9 MW) and electron cyclotron (EC) (up to 0.8 MW) radio-frequency waves. ITBs occur during either the current plateau or the ramp-up phase, both in full and partial current drive (CD) regimes, up to n{sub e0} > 1.4 x 10{sup 20} m{sup -3}, relevant to ITER operation. Central electron temperatures T{sub e0} > 8 keV, at n{sub e0} [approximately equal to] 0.8 x 10{sup 20} m{sup -3}, are sustained for up to 36 confinement times. The ITB extends over a region where a slightly reversed magnetic shear is established by off-axis LHCD and can be even larger than r/a = 0.5. EC power is used either to benefit from this improved confinement by heating inside the ITB or to enhance the peripheral LH power deposition and CD with off-axis resonance. Collisional ion heating is also observed, but thermal equilibrium with the electrons is not attained since the electron-ion equipartition time is always 4 to 5 times longer than the energy confinement time. An extensive transport modeling of these discharges, performed by means of the ASTRA code, is also presented. During the ITB phase, the ion diffusivity is close to the neoclassical value while the electron shear-dependent Bohm-gyro-Bohm model accounts quite well for T{sub e}(r,t), The Ray Tracing Fokker-Planck model, used to describe the LHCD physics, appears satisfactory to analyze and interpret the experimental results. It turns out that the barrier radius is mainly influenced by the LHCD deposition. In particular, a wider barrier is obtained the lower q{sub a} is and the larger the plasma density is.

  6. Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

    SciTech Connect

    Gao, Q. D.; Budny, R. V.

    2015-03-15

    By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (T{sub i,e}) and toroidal velocity (V{sub ϕ}) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LH driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition.

  7. 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.

  8. 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.

  9. Performance of the PBX-M passive plate stabilization system

    SciTech Connect

    Kugel, H.W.; Bell, R.; Bernabei, S.

    1994-02-01

    The PBX-M passive plate stabilization system provides significant stabilization of long-wavelength external kink modes, the slowing of vertical instability growth rates, and the amelioration of disruption characteristics. The passive plate stabilization system has allowed the use of LHCD and IBW to induce current density and pressure profile modifications, and m = 1 divertor biasing for modifying edge plasma transport. Improvements in the passive plate system insulators and support structures have provided reliable operation. Impurity influxes with the close-fitting passive plates are low. Solid target boronization is applied routinely to reduce conditioning time and maintain clean conditions.

  10. Motional Stark Effect Measurements of q-Profiles in JET Optimised Shear Plasmas

    NASA Astrophysics Data System (ADS)

    Stratton, B. C.; Hawkes, N. C.; Challis, C. D.; Drozdov, V.; Lomas, P.; Joffrin, E.; Litaudon, X.; Lotte, P.; Mazon, D.; Deangelis, R.; Rachlew, E.; Reyes-Cortes, S.

    2000-10-01

    A Motional Stark Effect (MSE) diagnostic is used to measure the magnetic field pitch angle in JET discharges. The q-profile is deduced from EFIT magnetic equilibrium reconstructions constrained by MSE data. Measurements have concentrated primarily on the Optimised Shear (OS) regime in which the details of the q-profile play an important role in the formation of internal transport barriers, leading to improved confinement. q-profiles in the target and high-power phases of OS plasmas with various heating scenarios (NBI + ICRF, NBI only, and NBI + LHCD) and pre-heat timings are presented and are correlated with ITB formation in the high-power phase.

  11. 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.

  12. 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.

  13. Design and coupling characteristics of lower-hybrid launcher for TPX

    SciTech Connect

    Hubbard, A.E.; Porkolab, M. ); Bernabei, S.; Greenough, N. ); Goranson, P.; Swain, D.; Yugo, J. )

    1994-10-15

    The physics and mechanical design of the LHCD launcher for the proposed TPX experiment is presented. The main role of this system is current drive and current profile control, requiring a flexible and well defined spectrum. The launcher features 32 independently phasable guides in each of 4 rows. Coupling calculations indicate that low reflection coefficients can be achieved over the whole range of phasing by adjusting the launcher position. Good directivity is predicted over a wide range of densities. The mechanical design of the launcher is complicated by the high expected thermal loads and radiation fluxes. A design which incorporates these requirements is outlined.

  14. Design and coupling characteristics of lower-hybrid launcher for TPX

    NASA Astrophysics Data System (ADS)

    Hubbard, A. E.; Porkolab, M.; Bernabei, S.; Greenough, N.; Goranson, P.; Swain, D.; Yugo, J.

    1994-10-01

    The physics and mechanical design of the LHCD launcher for the proposed TPX experiment is presented. The main role of this system is current drive and current profile control, requiring a flexible and well defined spectrum. The launcher features 32 independently phasable guides in each of 4 rows. Coupling calculations indicate that low reflection coefficients can be achieved over the whole range of phasing by adjusting the launcher position. Good directivity is predicted over a wide range of densities. The mechanical design of the launcher is complicated by the high expected thermal loads and radiation fluxes. A design which incorporates these requirements is outlined.

  15. A 3 megawatt lower hybrid generator for TPX

    SciTech Connect

    Greenough, N.; Bernabei, S.; Swain, D.

    1995-12-31

    The lower hybrid (LH) system is part of an overall heating and current drive system for TPX. The LH system is required to provide off-axis current profile control, efficient bulk current drive at low plasma temperatures, and electron heating. The device and facility will provide 4 MW of generated LH/LHCD power with 3 MW of power to the plasma at 3.7 GHz through one horizontal port. This paper will describe the RF generator system that supplies RF power to the launcher. The LH launcher is described separately in a paper by Paul Goranson of ORNL.

  16. Particle Confinement Properties of Lower Hybrid Current Drive Plasma on the HL-1 Tokamak

    NASA Astrophysics Data System (ADS)

    Duan, Xuru; Yuan, Chengjie; Qian, Shangjie; Ding, Xuantong; Yuan, Bin; Yang, Guang; Diao, Guangyue

    1994-03-01

    The particle confinement property of LHCD (lower hybrid current drive) plasma on the HL-1 tokamak is mainly affected by the line-averaged density of electrons (ne). With ne < 2.0 × 1013 cm-3, the particle confinement time (τp) is improved with the suppression of Hα(Dα) fluctuation at the edge, and tends to increase with the power PLH. The peak of τp appears near the critical density (1.0×1013 cm-3). These results are not influenced by the current drive directions.

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

    SciTech Connect

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

    2009-11-26

    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.

  18. C-Band All-Sky Survey: a first look at the Galaxy

    NASA Astrophysics Data System (ADS)

    Irfan, M. O.; Dickinson, C.; Davies, R. D.; Copley, C.; Davis, R. J.; Ferreira, P. G.; Holler, C. M.; Jonas, J. L.; Jones, Michael E.; King, O. G.; Leahy, J. P.; Leech, J.; Leitch, E. M.; Muchovej, S. J. C.; Pearson, T. J.; Peel, M. W.; Readhead, A. C. S.; Stevenson, M. A.; Sutton, D.; Taylor, Angela C.; Zuntz, J.

    2015-04-01

    We present an analysis of the diffuse emission at 5 GHz in the first quadrant of the Galactic plane using two months of preliminary intensity data taken with the C-Band All-Sky Survey (C-BASS) northern instrument at the Owens Valley Radio Observatory, California. Combining C-BASS maps with ancillary data to make temperature-temperature plots, we find synchrotron spectral indices of β = -2.65 ± 0.05 between 0.408 and 5 GHz and β = -2.72 ± 0.09 between 1.420 and 5 GHz for -10° < |b| < -4°, 20° < l < 40°. Through the subtraction of a radio recombination line free-free template, we determine the synchrotron spectral index in the Galactic plane (|b| < 4°) to be β = -2.56 ± 0.07 between 0.408 and 5 GHz, with a contribution of 53 ± 8 per cent from free-free emission at 5 GHz. These results are consistent with previous low-frequency measurements in the Galactic plane. By including C-BASS data in spectral fits, we demonstrate the presence of anomalous microwave emission (AME) associated with the H II complexes W43, W44 and W47 near 30 GHz, at 4.4σ, 3.1σ and 2.5σ, respectively. The CORNISH (Co-Ordinated Radio `N' Infrared Survey for High mass star formation) VLA 5-GHz source catalogue rules out the possibility that the excess emission detected around 30 GHz may be due to ultracompact H II regions. Diffuse AME was also identified at a 4σ level within 30° < l < 40°, -2° < b < 2° between 5 and 22.8 GHz.

  19. VizieR Online Data Catalog: Parameters of radio sources near Sgr A* (Yusef-Zadeh+, 2015)

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, F.; Roberts, D. A.; Wardle, M.; Cotton, W.; Schodel, R.; Royster, M. J.

    2017-09-01

    Radio continuum observations were carried out with the Karl G. Jansky Very Large Array (VLA) in its A-configuration at 34.5 GHz on 2014 March 9 (14A-232). We observed a field of view with a radius of 39'' centered on Sgr A* in the Ka band (8.7 mm) using the 3 bit sampler system, which provided full polarization correlations in four basebands, each 2 GHz wide, centered at 31.5, 33.5, 35.5, and 37.5 GHz. Each baseband was composed of 16 subbands 128 MHz wide. Each subband was composed of 64 channels, each 2 MHz wide. (1 data file).

  20. 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.

  1. Low Temperature Plasmas Generated and Sustained Indefinitely Using a Focused Microwave Beam

    NASA Astrophysics Data System (ADS)

    Reid, Remington; Hoff, Brad; Lepell, Paul; AFRL Team

    2016-10-01

    The Air Force Research Laboratory has constructed a device that can initiate a plasma discharge in a focused microwave beam and sustain it indefinitely. A 10 kW, 4.5 GHz beam is passed through a vacuum chamber outfitted with pressure windows that are transparent to 4.5 GHz radiation. The pressure windows are large enough in diameter to prevent any interactions between the beam and the metallic chamber. The entire experiment is housed inside an anechoic chamber to minimize reflections. This novel plasma source generates low temperature, low density plasmas that have no contact with the walls which minimizes contamination and sheath formation.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Impact of SOL plasma profiles on lower hybrid current drive: Experimental evidence, mitigation and modeling approaches

    NASA Astrophysics Data System (ADS)

    Shiraiwa, S.; Baek, S. G.; Faust, I.; Wallace, G.; Bonoli, P.; Meneghini, O.; Mumgaard, R.; Parker, R.; Scott, S.; Harvey, R. W.; Ding, B. J.; Li, M. H.; Lin, S. Y.; Yang, C.

    2015-12-01

    Recent progress in understanding and mitigating parasitic wave absorption in edge plasmas is presented. Experimental observations collected on Alcator C-Mod suggest multiple physics mechanisms are involved in such losses. Localized measurement of parametric decay instabilities (PDIs) has been performed using RF Langmuir probes. The divertor heat flux due to LH and ionization power loss have been evaluated quantitatively. We observe that the LHCD efficiency can be recovered when the SOL density profile is controlled by operating the tokamak at high current. The experimental progresses motivated a re-examination of the LHCD simulation model based on the ray-tracing/Fokker-Planck code (GENRAY/CQL3D). The effect of introducing a relatively small wave number broadening in the launched power spectrum and using 2D SOL density and temperature profiles was investigated. Comparison with C-Mod experiment indicates that the new model can explain the experimental trend over a wider density range including the density regime where disagreement was seen previously, suggesting that including realistic SOL geometry is a key to improve the simulation accuracy.

  7. Integrated Plasma Simulation of Ion Cyclotron and Lower Hybrid Range of Frequencies Actuators in Tokamaks

    NASA Astrophysics Data System (ADS)

    Bonoli, P. T.; Shiraiwa, S.; Wright, J. C.; Harvey, R. W.; Batchelor, D. B.; Berry, L. A.; Chen, Jin; Poli, F.; Kessel, C. E.; Jardin, S. C.

    2012-10-01

    Recent upgrades to the ion cyclotron RF (ICRF) and lower hybrid RF (LHRF) components of the Integrated Plasma Simulator [1] have made it possible to simulate LH current drive in the presence of ICRF minority heating and mode conversion electron heating. The background plasma is evolved in these simulations using the TSC transport code [2]. The driven LH current density profiles are computed using advanced ray tracing (GENRAY) and Fokker Planck (CQL3D) [3] components and predictions from GENRAY/CQL3D are compared with a ``reduced'' model for LHCD (the LSC [4] code). The ICRF TORIC solver is used for minority heating with a simplified (bi-Maxwellian) model for the non-thermal ion tail. Simulation results will be presented for LHCD in the presence of ICRF heating in Alcator C-Mod. [4pt] [1] D. Batchelor et al, Journal of Physics: Conf. Series 125, 012039 (2008).[0pt] [2] S. C. Jardin et al, J. Comp. Phys. 66, 481 (1986).[0pt] [3] R. W. Harvey and M. G. McCoy, Proc. of the IAEA Tech. Comm. Meeting on Simulation and Modeling of Therm. Plasmas, Montreal, Canada (1992).[0pt] [4] D. Ignat et al, Nucl. Fus. 34, 837 (1994).[0pt] [5] M. Brambilla, Plasma Phys. and Cont. Fusion 41,1 (1999).

  8. Evaluation of current drive requirements and operating characteristics of a high bootstrap fraction advanced tokamak reactor

    NASA Astrophysics Data System (ADS)

    Houlberg, W. A.; Attenberger, S. E.

    The reactor potential of some advanced physics operating modes proposed for the TPX physics program are examined. A moderate aspect ratio (A = 4.5 as in TPX), 2 GW reactor is analyzed because of its potential for steady-state, noninductive operation with high bootstrap current fraction. Particle, energy, and toroidal current equations are evolved to steady-state conditions using the 1 1/2-D time-dependent WHIST transport code. The solutions are therefore consistent with particle, energy, and current sources and assumed transport models. Fast wave current drive (FWCD) provides the axial seed current. The bootstrap current typically provides 80-90% of the current, while feedback on the lower hybrid current drive (LHCD) power maintains the total current. The sensitivity of the plasma power amplification factor, Q equivalent to P(sub fus)/P(sub aux), to variations in the plasma properties is examined. The auxiliary current drive power, P(sub aux) = P(sub LH) + P(sub FW); bootstrap current fraction; current drive efficiency; and other parameters are evaluated. The plasma is thermodynamically stable for the energy confinement model assumed (a multiple of ITER89P). The FWCD and LHCD sources provide attractive control possibilities, not only for the current profile, but also for the total fusion power since the gain on the incremental auxiliary power is typically 10-30 in these calculations when overall Q approximately equals 30.

  9. Evaluation of current drive requirements and operating characteristics of a high bootstrap fraction advanced tokamak reactor

    SciTech Connect

    Houlberg, W.A.; Attenberger, S.E.

    1994-11-01

    The reactor potential of some advanced physics operating modes proposed for the TPX physics program are examined. A moderate aspect ratio (A = 4.5 as in TPX), 2 GW reactor is analyzed because of its potential for steady-state, non-inductive operation with high bootstrap current fraction. Particle, energy and toroidal current equations are evolved to steady-state conditions using the 1-1/2-D time-dependent WHIST transport code. The solutions are therefore consistent with particle, energy and current sources and assumed transport models. Fast wave current drive (FWCD) provides the axial seed current. The bootstrap current typically provides 80-90% of the current, while feedback on the lower hybrid current drive (LHCD) power maintains the total current. The sensitivity of the plasma power amplification factor, Q {triple_bond} P{sub fus}/P{sub aux}, to variations in the plasma properties is examined. The auxiliary current drive power, P{sub aux} = P{sub LH} + P{sub FW}; bootstrap current fraction; current drive efficiency; and other parameters are evaluated. The plasma is thermodynamically stable for the energy confinement model assumed (a multiple of ITER89P). The FWCD and LHCD sources provide attractive control possibilities, not only for the current profile, but also for the total fusion power since the gain on the incremental auxiliary power is typically 10-30 in these calculations when overall Q {approx} 30.

  10. Investigation of runaway electrons in the current ramp-up by a fully non-inductive lower hybrid current drive on the EAST tokamak

    NASA Astrophysics Data System (ADS)

    Lu, H. W.; Zha, X. J.; Zhong, F. C.; Hu, L. Q.; Zhou, R. J.; EAST Team

    2013-05-01

    The possibility of using a lower hybrid wave (LHW) to ramp up the plasma current (Ip) from a low level to a high enough level required for fusion burn in the EAST (experimental advanced superconducting tokamak) tokamak is examined experimentally. The focus in this paper is on investigating how the relevant plasma parameters evolve during the current ramp-up (CRU) phase driving by a lower hybrid current drive (LHCD) with poloidal field (PF) coil cut-off, especially the behaviors of runaway electrons generated during the CRU phase. It is found that the intensity of runaway electron emission increases first, and then decreases gradually as the discharge goes on under conditions of PF coil cut-off before LHW was launched into plasma, PF coil cut-off at the same time as LHW was launched into plasma, as well as PF coil cut-off after LHW was launched into plasma. The relevant plasma parameters, including Hα line emission (Ha), impurity line emission (UV), soft x-ray emission and electron density n_{\\rm{e}} , increase to a high level. The loop voltage decreases from positive to negative, and then becomes zero because of the cut-off of PF coils. Also, the magnetohydrodynamic activity takes place during the CRU driving by LHCD.

  11. A control-oriented model of the current profile in tokamak plasma

    NASA Astrophysics Data System (ADS)

    Witrant, E.; Joffrin, E.; Brémond, S.; Giruzzi, G.; Mazon, D.; Barana, O.; Moreau, P.

    2007-07-01

    This paper proposes a control-oriented approach to the tokamak plasma current profile dynamics. It is established based on a consistent set of simplified relationships, in particular for the microwave current drive sources, rather than exact physical modelling. Assuming that a proper model for advanced control schemes can be established using the so-called cylindrical approximation and neglecting the diamagnetic effects, we propose a model that focuses on the flux diffusion (from which the current profile is inferred). Its inputs are some real-time measurements available on modern tokamaks and the effects of some major actuators, such as the magnetic coils, lower hybrid (LHCD), electron and ion cyclotron frequency (ECCD and ICRH) systems, are particularly taken into account. More precisely, the non-inductive current profile sources are modelled as 3-parameters functions of the control inputs derived either from approximate theoretical formulae for the ECCD and bootstrap terms or from experimental scaling laws specifically developed from hard x-ray Tore Supra data for the LHCD influence. The use of scaling laws in this model reflects the fact that the operation of future reactors will certainly depend upon a great number of scaling laws and specific engineering parameters. The discretization issues are also specifically addressed, to ensure robustness with respect to discretisation errors and the efficiency (in terms of computation time) of the associated algorithm. This model is compared with experimental results and the CRONOS solver for tore supra tokamak.

  12. Optimizing the current ramp-up phase for the hybrid ITER scenario

    NASA Astrophysics Data System (ADS)

    Hogeweij, G. M. D.; Artaud, J.-F.; Casper, T. A.; Citrin, J.; Imbeaux, F.; Köchl, F.; Litaudon, X.; Voitsekhovitch, I.; the ITM-TF ITER Scenario Modelling Group

    2013-01-01

    The current ramp-up phase for the ITER hybrid scenario is analysed with the CRONOS integrated modelling suite. The simulations presented in this paper show that the heating systems available at ITER allow, within the operational limits, the attainment of a hybrid q profile at the end of the current ramp-up. A reference ramp-up scenario is reached by a combination of NBI, ECCD (UPL) and LHCD. A heating scheme with only NBI and ECCD can also reach the target q profile; however, LHCD can play a crucial role in reducing the flux consumption during the ramp-up phase. The optimum heating scheme depends on the chosen transport model, and on assumptions of parameters like ne peaking, edge Te,i and Zeff. The sensitivity of the current diffusion on parameters that are not easily controlled, shows that development of real-time control is important to reach the target q profile. A first step in that direction has been indicated in this paper. Minimizing resistive flux consumption and optimizing the q profile turn out to be conflicting requirements. A trade-off between these two requirements has to be made. In this paper it is shown that fast current ramp with L-mode current overshoot is at the one extreme, i.e. the optimum q profile at the cost of increased resistive flux consumption, whereas early H-mode transition is at the other extreme.

  13. Evaluation of current drive requirements and operating characteristics of a high bootstrap fraction advanced tokamak reactor

    SciTech Connect

    Houlberg, W.A.; Attenberger, S.E.

    1995-02-01

    The reactor potential of some advanced physics operating modes proposed for the TPX physics program are examined. A moderate aspect ratio (A = 4.5 as in TPX), 2 GW reactor is analyzed because of its potential for steady-state, non-inductive operation with high bootstrap current fraction. Particle, energy and toroidal current equations are evolved to steady-state conditions using the 1-1/2-D time-dependent WHIST transport code. The solutions are therefore consistent with particle, energy and current sources and assumed transport models. Fast wave current drive (FWCD) provides the axial seed current. The bootstrap current typically provides 80-90% of the current, while feedback on the lower hybrid current drive (LHCD) power maintains the total current. The sensitivity of the plasma power amplification factor, Q {equivalent_to} P{sub fus}/P{sub aux}, to variations in the plasma properties is examined. The auxiliary current drive power, P{sub aux} = P{sub LH} + P{sub FW}; bootstrap current fraction: current drive efficiency; and other parameters are evaluated. The plasma is thermodynamically stable for the energy confinement model assumed (a multiple of ITER89P). The FWCD and LHCD sources provide attractive control possibilities, not only for the current profile, but also for the total fusion power since the gain on the incremental auxiliary power is typically 10-30 in these calculations when overall Q {approx} 30.

  14. Magnetic perturbation effects on boundary plasmas during high power lower hybrid current drive in Tore Supra

    NASA Astrophysics Data System (ADS)

    Evans, T. E.; Goniche, M.; Grosman, A.; Guilhem, D.; Hess, W.; Vallet, J.-C.

    1992-12-01

    Small time-independent magnetic perturbations (δ br), produced with the Tore Supra ergodic divertor coils, have been used to control thermal loads on plasma facing components, current density profiles, the transport of non-Maxwellian particles, and the confinement properties of thermal plasmas during high power ( PLH≤3.3 MW) lower hybrid current drive (LHCD) discharges. MARFEs with 0.12 ≤ϱ m=π a2 < ne20> Ip-1≤0.22 (i.e., roughly a factor of 3 less than the smallest value of ϱ m previously reported) are obtained during the δ br pulse when PLH>2.0 MW and the edge safety factor is slightly less than 3. These MARFEs generally appear to have the same characteristics as high ϱ m MARFEs and are positionally stable throughout the LHCD+δ br pulse. Steady state conditions in which more than 90% of the total input power is radiated from a 0.15 m wide region near the high-field side wall were obtained.

  15. Development of high poloidal beta, steady-state scenario with ITER-like W divertor on EAST

    NASA Astrophysics Data System (ADS)

    Garofalo, A. M.; Lanctot, M.; Gong, X. Z.; Ding, S.; Li, G.; Liu, H.; Lyu, B.; Qian, J.; Bonoli, P. T.; Shiraiwa, S.; Holcomb, C.; McClenaghan, J.

    2016-10-01

    Experiments on EAST have started to adapt the fully-noninductive high poloidal beta scenario developed on DIII-D, in order to demonstrate steady state tokamak operation at high performance on metal walls. Unlike on DIII-D, where the creation of a broad current profile requires early heating at low density, on EAST a broad current profile can be obtained simply by increasing the electron density, when most of the current drive is provided by lower hybrid wave. Systematic scans yield lower internal inductance with higher density. The hypothesis is that the LHCD profile becomes more off-axis with higher density. With the newly commissioned POINT (polarimeter-interferometer) diagnostic for q-profile measurements, these experiments enable strict tests of LHCD deposition models. Supported by US DOE under DE-SC0010685, DE-SC0010492 DE-FC02-04ER54698, DE-AC02-09-CH11466, DE-AC52-07NA27344, DE-AC05-00OR22725, and the National Magnetic Confinement Fusion Program of China (No. 2015GB110001 and 2015GB102000).

  16. Transition into the improved core confinement mode as a possible mechanism for additional electron heating observed in the lower hybrid current drive experiments at the FT-2 tokamak

    NASA Astrophysics Data System (ADS)

    Lashkul, S. I.; Altukhov, A. B.; Gurchenko, A. D.; Gusakov, E. Z.; Dyachenko, V. V.; Esipov, L. A.; Irzak, M. A.; Kantor, M. Yu.; Kouprienko, D. V.; Perevalov, A. A.; Saveliev, A. N.; Stepanov, A. Yu.; Shatalin, S. V.

    2017-07-01

    In experiments on lower hybrid current drive (LHCD) carried out at the FT-2 tokamak, a substantial increase in the central electron temperature T e ( r = 0 cm) from 550 to 700 eV was observed. A complex simulation procedure is used to explain a fairly high LHCD efficiency and the observed additional heating, which can be attributed to a transition into the improved core confinement (ICC) mode. For numerical simulations, data obtained in experiments with deuterium plasma at < n e > = 1.6 × 1019 m-3 were used. Simulations by the GRILL3D, FRTC, and ASTRA codes have shown that the increase in the density and central temperature is apparently caused by a significant suppression of heat transport in the electron component. The mechanism for transition into the improved confinement mode at r < 3 cm can be associated with the broadening of the plasma current channel due to the lower hybrid drive of the current carried by superthermal and runaway electrons. In this case, the magnetic shear s = ( r/ q)( dq/ dr) in the axial region of the plasma column almost vanishes during the RF pulse. In this study, the effect of lower hybrid waves on the plasma parameters, resulting in a transition into the ICC mode, is considered. New experimental and calculated data are presented that evidence in favor of such a transition. Special attention is paid to the existence of a threshold for the transition into the ICC mode in deuterium plasma.

  17. 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.

  18. 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.

  19. 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.

  20. 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}.

  1. 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

  2. Beyond where to how: a machine learning approach for sensing mobility contexts using smartphone sensors.

    PubMed

    Guinness, Robert E

    2015-04-28

    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. Iron based carbon nanocomposites for electromagnetic wave absorber with wide bandwidth in GHz range

    NASA Astrophysics Data System (ADS)

    Liu, J. R.; Itoh, M.; Horikawa, T.; Taguchi, E.; Mori, H.; Machida, K.

    2006-02-01

    The electromagnetic wave absorption properties of resin compacts containing 40 vol. % composite powders of α-Fe/C(a), and Fe3C/C(a) were characterized in a frequency range of 0.05 26.5 GHz, according to a conventional reflection/transmission technique. The real part (ɛr ') and the imaginary part (ɛr '') of relative permittivity were constantly low in the 2 14 GHz (ɛr '= ˜12.4 and ɛr ''= ˜0.6) for α-Fe/C(a) resin composites, and in the 1 26.5 GHz (ɛr '= ˜9.6 and ɛr ''= ˜0.8) for Fe3C/C(a) ones. The imaginary part (μr '') of relative permeability exhibited wide peaks in the 1 9 GHz range for α-Fe/C(a), and in the 2 26.5 GHz range for Fe3C/C(a) owing to their different magnetocrystalline anisotropy field values. Consequently, the resin compacts with 40 vol. % α-Fe/C(a), and Fe3C/C(a) powders provided good electromagnetic wave absorption performances (reflection loss <-20 dB) in ranges of 4.3 8.2 GHz, and 9 26.5 GHz over absorber thicknesses of 1.8 3.3 mm, and 1.0 2.4 mm, respectively.

  4. Radio Observations of the Nuclear Transient AT 2017gbl in IRAS 23436+5257

    NASA Astrophysics Data System (ADS)

    Bright, Joe; Fender, Rob; Anderson, Gemma; Cantwell, Therese

    2017-08-01

    We report on observations of AT 2017gbl made at 15.5 GHz with the Arcminute Microkelvin Imager Large Array (AMI-LA). AT 2017gbl was discovered (ATel #10651) in the near-infrared on MJD 57942.56 and associated with the nucleus of the galaxy IRAS 23436+5257.

  5. Millimetre-wave isolator based on Al substituted Ba ferrite

    NASA Astrophysics Data System (ADS)

    Ustinov, A. B.; Vinnik, D. A.; Belyavskii, P. Yu; Gudkova, S. A.; Zakharchuk, I.; Lähderanta, E.

    2016-11-01

    A mm-wave isolator is fabricated and studied. The operating frequency of the devices is 78.5 GHz. A bandwidth at the level of -3 dB equals 1.6 GHz. The device used a flux grown single-crystal aluminum substituted barium ferrite.

  6. 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

    ... 3550-3650 MHz band (3.5 GHz Band) for shared, commercial uses, including small cell networks. The NPRM... federal and Fixed Satellite System (FSS) users, potential out-of-band interference issues, or any... capabilities of small cell and SAS technologies to enable sharing between users in the Priority Access and...

  7. 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...

  8. 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.

  9. 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.

  10. 75 FR 7975 - Procedures to Govern the Use of Satellite Earth Stations on Board Vessels in the 5925-6425 MHz...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-23

    ... COMMISSION 47 CFR Part 25 Procedures to Govern the Use of Satellite Earth Stations on Board Vessels in the... Satellite Earth Stations on Board Vessels in the 5925-6425 MHz/3700-4200 MHz Bands and 14.0-14.5 GHz/11.7-12.... Expiration Date: December 31, 2012. Title: Earth Stations on Board Vessels (ESV). Form No.: Not...

  11. 78 FR 14952 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ... COMMISSION 47 CFR Part 2 Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service... of Earth Stations Aboard Aircraft (ESAA) in the 14.0-14.5 GHz band from secondary to primary and... stations of the FSS on a primary basis in the 11.7-12.2 GHz band (space-to-Earth), on an unprotected...

  12. 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

    ... information shall demonstrate that the proposed NGSO FSS system would not exceed the validation equivalent... Service (NGSO FSS) system in the 10.7-14.5 GHz bands. The technical information shall demonstrate that the... request at any time additional information from the NGSO FSS system applicant or licensee concerning the...

  13. New small 90 deg hybrid coupler

    NASA Astrophysics Data System (ADS)

    Murgulescu, M.-H.; Legaud, P.; Penard, E.; Zaquine, I.

    1994-08-01

    The two classical 90 deg couplers (Lange coupler and branch-line hybrid) are not appropriate for frequencies around 1-5 GHz. The small 90 deg coupler proposed by the authors is the implementation of the Wheatstone bridge in uniplanar transmission lines. It is dedicated to narrowband applications. The coupler is demonstrated at a center frequency of 4 GHz.

  14. Spike Leakage and Burnout of Silicon PIN Diode Microwave Limiters

    DTIC Science & Technology

    1991-06-01

    13 3.4 Video Pulse Measurements...p m-width diodes ........................................................................ 15 11. Measured recovery time versus forward-current pulse ...38 43. Comparison of measured short pulse and cw output power as a function of input power at 1.5 GHz for 10-jim diode

  15. VSOP Observations of the Blazar S5 2007+77

    NASA Astrophysics Data System (ADS)

    Gabányi, K. É.; Krichbaum, T. P.; Kraus, A.; Witzel, A.; Zensus, J. A.

    2009-08-01

    The blazar, S5 2007+77 shows intraday variability in cm wavelengths. Seven epochs of VSOP observations were carried out in 1998 and 1999 at 5 GHz to look for the origin of the variability with the highest achievable angular resolution at cm wavelengths. Here the results of four epochs are analysed, which revealed ˜ 10 % variations in polarized flux density.

  16. Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser

    NASA Technical Reports Server (NTRS)

    Auyeung, J.

    1981-01-01

    We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.

  17. Sub-femtosecond absolute timing jitter with a 10 GHz hybrid photonic-microwave oscillator

    NASA Astrophysics Data System (ADS)

    Fortier, T. M.; Nelson, C. W.; Hati, A.; Quinlan, F.; Taylor, J.; Jiang, H.; Chou, C. W.; Rosenband, T.; Lemke, N.; Ludlow, A.; Howe, D.; Oates, C. W.; Diddams, S. A.

    2012-06-01

    We present an optical-electronic approach to generating microwave signals with high spectral purity. By circumventing shot noise and operating near fundamental thermal limits, we demonstrate 10 GHz signals with an absolute timing jitter for a single hybrid oscillator of 420 attoseconds (1 Hz-5 GHz).

  18. VizieR Online Data Catalog: Gould's Belt Distances Survey (GOBELINS). II. OMC (Kounkel+, 2017)

    NASA Astrophysics Data System (ADS)

    Kounkel, M.; Hartmann, L.; Loinard, L.; Ortiz-Leon, G. N.; Mioduszewski, A. J.; Rodriguez, L. F.; Dzib, S. A.; Torres, R. M.; Pech, G.; Galli, P. A. B.; Rivera, J. L.; Boden, A. F.; Evans, N. J., II; Briceno, C.; Tobin, J. J.

    2017-07-01

    The observations presented in this paper were made with the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA) at 5GHz with a 256MHz bandwidth (spanning the range of 4.852-5.076GHz). They span a period of two years from 2014 to 2016 March. (2 data files).

  19. Dielectric spectroscopy as a probe for dynamic properties of compacted smectites

    NASA Astrophysics Data System (ADS)

    Cadène, A.; Rotenberg, B.; Durand-Vidal, S.; Badot, J.-C.; Turq, P.

    The micro-dynamics of water and ions in two types of clays (montmorillonite and hectorite) was investigated with broadband dielectric spectroscopy (40 Hz to 5 GHz). Four to five relaxations were observed depending on the relative humidity, the clay type and the nature of the compensating counter-ion (Na + or Cs +). A tentative assignment of the relaxations to physical mechanisms is proposed.

  20. Joint timing/frequency offset estimation and correction based on FrFT encoded training symbols for PDM CO-OFDM systems.

    PubMed

    Zhou, Huibin; Li, Xiang; Tang, Ming; Wu, Qiong; Chen, Xi; Luo, Ming; Fu, Songnian; Liu, Deming

    2016-12-12

    A joint timing offset (TO) and frequency offset (FO) estimation algorithm is proposed for polarization division multiplexing (PDM) coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems. It is realized by taking the advantage of the time-frequency property of the fractional Fourier transformation (FrFT) encoded training symbols. Compared with the classical Schmidl & Cox method, the proposed algorithm exhibits robust estimation result of timing offset with poor optical signal-to-noise ratio (OSNR) and nonlinear interference. For the frequency offset estimation, a quite large FO estimation ranges of [-5GHz + 5GHz] can be achieved. The mean normalized estimation error can be kept under 0.002 and the max normalized estimation error is no more than 0.008. The feasibility and effectiveness of the proposed joint estimation algorithm has been verified by experiments. The transmission performances with [-5GHz + 5GHz] FO are compared under the OSNR range from 14 to 27dB in a 106.8Gbit/s 16-ary quadrature amplitude modulation (16-QAM) PDM CO-OFDM transmission system. The proposed TO/FO estimation algorithm performs robustly and accurately without any induced BER degradations.