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Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on

Date 2-9 Sept. 2007

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Displaying Results 1 - 25 of 472
  • Preface

    Page(s): iii
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  • Sponsors

    Page(s): vii
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  • Program summary

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  • IRMMW-THz2007

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  • IRMMW-THz2007

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  • [Copyright notice]

    Page(s): i
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  • Contents

    Page(s): ii
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  • Conference committees

    Page(s): iv - vi
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  • Submitting author index

    Page(s): A1 - A7
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  • Are there terahertz solutions to problems in understanding the physics of life?

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (137 KB) |  | HTML iconHTML  

    This article provides a very brief summary of some of the problems concerned with understanding the physics of life. It then speculates on the contribution that research with the new high power sources of terahertz radiation might make to investigating some of these problems. View full abstract»

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  • Gyrotrons and mm wave technology for ITER

    Page(s): 4 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4573 KB) |  | HTML iconHTML  

    Recent progress on the high power mm wave technologies of the electron cyclotron heating and current drive (EC H&CD) for ITER (international thermonuclear experimental reactor) application is introduced. The R&D and design works are under progress at EU, Russia, US, India and Japan. On the 170 GHz gyrotron developments, the ITER criterion (1MW, 500s, 50%), which was the most critical issue for EC H&CD system, has been satisfied. Accompanied with the progress of the power sources, the development of the components is accelerated, such as mm wave transmission line. In addition, specific design works of launchers for mm-wave injection into the plasma have advanced. View full abstract»

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  • Advances in millimeter wave/THZ plasma diagnostics instrumentation

    Page(s): 8 - 11
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (13607 KB) |  | HTML iconHTML  

    Significant advances in millimeter wave and THz receiver and array technology have led to new approaches for the visualization of density and temperature fluctuations inside the core of high temperature plasmas. Electron cyclotron emission imaging collects millimeter wave electron cyclotron emission from the plasma and images it onto a planar mixer array to form 2-D images of electron temperature fluctuations. Illuminating the plasma with millimeter waves, microwave imaging reflectometry images the plasma cutoff layer onto a planar mixer array and thereby spatially resolves density fluctuations on the extended plasma cutoff surface; the use of multiple frequency illumination results in the formation of 2-D density fluctuation images. Collective scattering approaches at THz frequencies can resolve density fluctuations deep into the plasma core that are not accessible via reflectometry. View full abstract»

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  • Cosmic Microwave Background experiments — past, present and future

    Page(s): 12 - 15
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (896 KB) |  | HTML iconHTML  

    The cosmic microwave background (CMB) is the oldest electromagnetic radiation to reach the earth. Measurements of this radiation play a central role in modern Cosmology. In this presentation, I will describe the information that can be obtained from measurements of the CMB. The importance of these measurements is such that there have been two rounds of Nobel Prizes. The field has been advanced by small ground- and balloon-based measurements followed by space missions including COBE and WMAP. The Planck mission will be launched next year. A new generation of ground-based observations is now beginning, which may lead to yet another space mission. The requirements for such measurements have strongly driven the development of direct detection systems at millimeter and submillimeter wavelengths. The physical and practical issues that generally favor the use of coherent receivers (now based on HEMT amplifiers) at frequencies below -90 GHz and bolometric detectors at higher frequencies will be discussed. The development of this field will be illustrated by describing generic types of technology developments and of experiments. View full abstract»

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  • Far infrared fourier transform spectroscopy of solids

    Page(s): 16 - 19
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1764 KB) |  | HTML iconHTML  

    We briefly review the techniques of dispersive Fourier transform spectroscopy, polarised oblique incidence reflection spectroscopy and attenuated total reflection (ATR) spectroscopy, and discuss applications of these techniques to a variety of solids, including alkali halide crystals, ferroelectrics, semiconductors and insulating and conducting magnetic media. View full abstract»

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  • Unique applications of THz time-domain spectroscopy and waveguide THz-TDS

    Page(s): 20 - 23
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    THz photonic technology will be reviewed. Freely propagating THz-TDS and Waveguide THz-TDS measurements will be presented, which were previously impossible by other techniques. The unique features of THz-TDS for scientific measurements and technical applications will be illustrated. Future opportunities in fundamental research, and practical applications will be described. View full abstract»

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  • Terahertz quantum cascade lasers and video-rate THz imaging

    Page(s): 24 - 25
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (695 KB) |  | HTML iconHTML  

    Based on a robust THz gain medium that rapidly depopulates the lower state using resonant LO-phonons and a novel metal-metal waveguide structure for mode confinement, we have developed THz quantum-cascade lasers with many performance records. These include but not limited to: the highest pulsed operating temperature of ~170 K, the highest CW operating temperature of 117 K, long wavelength of ~190 mum, and the highest output power levels of-250 mW. Using these lasers and a 320 times 240 pixel focal-plane array camera, real-time THz imaging is performed at a video rate of 20 frames/second. View full abstract»

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  • Infrared nanoscopy

    Page(s): 26 - 30
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3092 KB) |  | HTML iconHTML  

    My contribution is to highlight a recent advance in the area of microscopy: infrared near-field microscopy of the scattering type (infrared s-SNOM). This ultra-resolving infrared microscopy has come quite as a surprise because the >3 mum wavelengths seemed to prohibit - from Abbe's rule - any sub-micrometer resolution. The realization of a 10-nm resolving infrared microscope enables the power of infrared spectroscopy to benefit future nanoscience research. View full abstract»

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  • Metamaterials and their THz applications

    Page(s): 30 - 33
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (603 KB) |  | HTML iconHTML  

    We present experimental results of metamaterials operating at terahertz and mm-wave frequencies. Metamaterials consist of a single layer of 200 nm thick gold on a doped or undoped semiconducting substrate. By optical and electronic doping of supporting semiconducting substrates we show external control of planar arrays of metamaterials, characterized with terahertz time domain spectroscopy. Both methods yield meta-material / semiconductor devices which can be utilized as switches or modulators, enabling modulation of THz transmission by 50 percent. Experiments are supported by simulations and results agree well. Because of the universality of metamaterial response over many decades of frequency, these results have implications for other regions of the electromagnetic spectrum and will undoubtedly play a key role in future demonstrations of novel high-performance devices. View full abstract»

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  • Recent advances and future prospects of THz quantum cascade lasers

    Page(s): 34 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2452 KB) |  | HTML iconHTML  

    The development of quantum cascade lasers (QCLs) operating at terahertz frequencies is proceeding at a rapid pace. Improvements have been obtained both in output power and operating temperatures, thanks to a combination of quantum design and fabrication methods, while the range of lasing frequencies has been extended below 1 THz. Distributed feedback devices have been fabricated with a variety of techniques for the purpose of achieving predictable single-mode emission, and external cavity set-ups have been implemented for tunability. THz QCLs have also become an important test-bed for new device concepts like non-periodic resonators, low volume microcavity lasers, and phase-matched non-linear devices that generate a THz signal on a near-IR carrier. Future developments will likely include optical circuits with photonic crystals, random lasers, new electro-mechanical tuning mechanisms, and possibly quantum dot lasers, further expanding the range of possible applications in many research areas. View full abstract»

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  • The European 2MW, 170GHz coaxial cavity gyrotron for ITER

    Page(s): 38 - 40
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4697 KB) |  | HTML iconHTML  

    In the reference ECH design, ITER requires a total of 20 MW/CW power at 170 GHz using gyrotrons with a unit power of 1 MW. A higher power per unit (2 MW/gyrotron) would result in a strong reduction of the cost of the whole ECRH system, and would also relax the room constraints on the launcher antenna design. The high power capability of coaxial cavity gyrotrons has been demonstrated with short pulse experiments at FZK. A collaborative effort between European research associations CRPP-EPFL, FZK and Thales Electron Devices (TED) has been launched by the European Fusion Development Agreement (EFDA) in 2003, aiming at the development of an industrial 170 GHz/2 MW/CW coaxial cavity gyrotron. The first prototype, although designed to be CW compatible is expected to reach 2 MW/ls and has been delivered by end of 2006. It will be tested in Lausanne, where a specially dedicated test facility has been built. The test facility has been designed to be flexible enough, allowing the possible commissioning of tubes with different characteristics, as well the tests of the launcher antenna at full performances. Initial experiments are planned for the end of the third quarter 2007. View full abstract»

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  • Recent results of development in Russia of high power gyrotrons

    Page(s): 41 - 43
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    The paper presents the latest achievements in development at IAP/GYCOM of MW power level gyrotrons for fusion installations. During last years several new gyrotrons were designed and tested at IAP/GYCOM. Among them are a new version of 170 GHz gyrotron for ITER and multi-frequency (105-140 GHz) gyrotrons for Asdex-Up. All these gyrotrons are equipped with diamond CVD windows and depressed collectors. View full abstract»

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  • New test results of 170 GHz/1MW/50%/CW gyrotron for ITER

    Page(s): 44 - 45
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1286 KB) |  | HTML iconHTML  

    The development of 170 GHz/1 MW/ 50%/CW gyrotron for ITER has been in progress in Russia. Recent test results of the last gyrotron version are presented. Stable output power of 0.5-0.6 MW was obtained for 300-s pulse duration limited by capability of the main power supply of that time. For output power of 0.9-0.95 MW the maximal pulse duration of 102 s was mainly limited by instability of gyrotron protection system and imperfection of power transmission line. Total gyrotron efficiency was about 50%. Stray radiation near 5% of radiated power was measured. After testing facility improvement and gyrotron opening and reassembling gyrotron test will be continued. View full abstract»

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  • Studies on a 120 GHz, 1.0 MW, longpulse gyrotron for plasma start-up in ITER

    Page(s): 46 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (924 KB) |  | HTML iconHTML  

    In this work, the initial design concept of a 1.0-1.5 MW, longpulse gyrotron operating at 120 GHz, for plasma start-up in the ITER has been presented. Mode competition and mode selection procedures are carried out for various candidate modes and the modes TE24,8 or TE24,7 are chosen as probable operating modes. Cold cavity design and self-consistent and time dependent calculations are carried out for the TE24,8 mode and power and efficiencies are computed. The nominal beam parameters are chosen to give a moderate to low velocity spread. The initial results are indicating that an output power of well over 1.0 MW, CW can be achieved at 120 GHz with the TE24,8 mode as the operating cavity mode. Further investigations to consolidate the design concept are in progress at the time of reporting this paper. View full abstract»

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  • Mode competition in the 170 GHz coaxial gyrotron cavity for ITER

    Page(s): 48 - 49
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (245 KB) |  | HTML iconHTML  

    170 GHz coaxial cavity gyrotrons with 2 MW output power in continuous wave (CW) operation are regarded as potential ECRH sources in ITER. A first industrial prototype of such a gyrotron has already been fabricated and delivered to CRPP Lausanne, where a suitable test facility has been constructed. Experimental tests are expected for the second half of this year. In view of the further development work, it is important to improve our understanding of the complicated processes of mode competition occurring in oversized coaxial cavities. An example of the comparison between the results obtained by means of four independent codes is presented and discrepancies between the theoretical end experimental results are discussed. View full abstract»

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  • Simulation of high power CW gyrotron collectors including the effect of secondary emission

    Page(s): 50 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (521 KB) |  | HTML iconHTML  

    High power CW gyrotrons (as the 1 MW, 140 GHz conventional cavity gyrotron for the stellarator W7-X at IPP Greifswald, Germany or the 2 MW, 170 GHz coaxial cavity gyrotron for ITER) require a sophisticated depressed collector design that is capable of absorbing the spent electron beam. The simulation program ESRAY, originally developed at FZK/IHM for electron gun design, is also capable of simulating gyrotron collectors, including the effects of eddy currents in the collector wall. At the moment, work is in progress to include secondary emission models in the ESRAY code. The effect of secondary emission has the advantage of a slightly reduced peak power density on the collector wall. It may also have drawbacks like secondary electrons reaching parts of the collector structure that are insufficiently cooled or electrons traveling back to the resonator region where they may have negative influence on the gyrotron interaction. In this paper we present the first results obtained with the enhanced version of our simulation tool ESRAY showing the effects of secondary emission on the collector wall of the 2 MW 170 GHz coaxial cavity gyrotron for ITER. View full abstract»

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