Showing papers in "International Journal of Infrared and Millimeter Waves in 2005"
TL;DR: The terahertz time domain spectroscopy (THz-TDS) as mentioned in this paper has been used extensively in the characterization of solids, such as semiconductors, superconductors, polymers, and photonic crystals.
Abstract: Recent development of the terahertz time domain spectroscopy (THz-TDS) and its application to solids have been reviewed. This spectroscopy is unique in that the time-domain wave forms are measured at first and the complex optical constants are deduced directly by the Fourier transformation of them without resort to the Kramers-Kronig analysis. Various types of the THz-TDS systems are briefly described. Applications of the THz-TDS to various solids, i.e., semiconductors, superconductors, polymers, photonic crystals, and so on are also presented to demonstrate how widely this spectroscopy is applicable to characterization of solids.
233 citations
TL;DR: In this article, the backward-wave oscillators (BWOs) were used for terahertz-sub-Terahertz (THz-subTHz) spectrometers, based on continuously frequency-tunable coherent sources of radiation.
Abstract: Modern Terahertz-subTerahertz (THz-subTHz) spectrometers, based on continuously frequency-tunable coherent sources of radiation, the backward-wave oscillators (BWOs), are described which cover the frequencies v = 1 cm−1 − 50 cm−1 (0.03 − 1.5 THz) and allow for measurements at temperatures 2 − 1000 K, also in magnetic fields. They allow for direct determination of spectra of any optical parameter of a material at millimeter-submillimeter wavelengths, the domain where infrared or microwave spectrometers encounter serious methodological difficulties. We report on new technical abilities of the quasioptical BWO-spectrometers and discuss their main components. We demonstrate abilities of the THz-subTHz BWO-spectroscopy by presenting some latest results on measurements of dielectric, conducting, superconducting and magnetic materials.
131 citations
TL;DR: In this article, the authors present the state-of-the-art and future prospects of gyro-devices and their applications, including high-power radar ranging and imaging in atmospheric and planetary science as well as deep-space and specialized satellite communications and RF drivers for next-generation high-gradient linear accelerators.
Abstract: Gyrotron oscillators are mainly used as high power millimeter wave sources for electron cyclotron resonance heating (ECRH), electron cyclotron current drive (ECCD), stability control and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. The maximum pulse length of commercially available 1 MW gyrotrons employing synthetic diamond output windows is 5 s at 110 GHz (CPI and JAERI-TOSHIBA), 12 s at 140 GHz (FZK-CRPP-CEA-TED) and 10 s at 170 GHz (GYCOM and JAERI-TOSHIBA), with efficiencies slightly above 30%. Total efficiencies of 45–50 % have been obtained using single-stage depressed collectors (SDC). The energy world record of 160 MJ (0.89 MW at 180 s pulse length and 140 GHz) at power levels higher than 0.8 MW has been achieved by the European FZK-CRPP-CEA-TED collaboration at FZK. Operation at the 1st and the 2nd harmonic of the EC frequency enables gyrotrons to act as medium power step-tunable mm- and sub-mm wave sources in the frequency range from 38 GHz (fundamental) to 889 GHz (2nd harmonic) for plasma diagnostics, EC plasma discharges for generation of multi-charged ions, high-frequency broadband electron paramagnetic resonance (EPR) spectroscopy and medical applications. Gyrotrons have also been successfully used in materials processing. Such technological applications require gyrotrons with the following parameters: f ≥ 24 GHz, Pout = 4–50 kW, CW, η ≥ 30%. Future applications which await the development of novel high-power gyro-amplifiers include high resolution radar ranging and imaging in atmospheric and planetary science as well as deep-space and specialized satellite communications and RF drivers for next-generation high-gradient linear accelerators (supercolliders). The present paper reviews the state-of-the-art and future prospects of gyro-devices and their applications.
103 citations
TL;DR: In this article, the principal bandwidth of such a two-polarizer setup has been evaluated and it was shown that two mirrors with sinusoidal grooves and corrugation depths adjusted to the center frequency of 122.5 GHz will satisfy the requirements.
Abstract: A new broadband ECRH (Electron Cyclotron Resonance Heating) system is currently under construction at the ASDEX Upgrade tokamak. This system will employ multi-frequency gyrotrons step-tunable in the range 105–140 GHz. A set of two corrugated polarizer mirrors will be applied to provide for an arbitrary polarization of the Gaussian beam injected into the plasma. The principal bandwidth of such a two-polarizer setup has been evaluated. It can be shown that two mirrors with sinusoidal grooves and corrugation depths adjusted to the center frequency of 122.5 GHz will satisfy the requirements.
38 citations
TL;DR: In this paper, a millimeter wave propagation experiment at 103 GHz (2.9 mm) on a propagation path of 390 m was conducted and the results were compared with the rain attenuation calculations from the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size.
Abstract: We have conducted a millimeter wave propagation experiment at 103 GHz (2.9 mm) on a propagation path of 390 m. The results were compared with the rain attenuation calculations from the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size. It has been shown that the Weibull distribution has a good agreement with the experiments.
29 citations
TL;DR: In this paper, reentrant circular cylindrical cavities are analyzed on the basis of a mathematically simple formalism extending the range of validity of expressions for resonant frequency and quality factor obtained from lumped RLC constant models.
Abstract: Of applications ranging from electron spin resonance to detection of gravitational waves, reentrant circular cylindrical cavities are analyzed on the basis of a mathematically simple formalism extending the range of validity of expressions for resonant frequency and quality factor obtained from lumped RLC constant models. Several cavity configurations in the 1 – 3 GHz range are analytically examined in excellent agreement with frequencies obtained from Superfish code.
29 citations
TL;DR: In this article, 24 GHz microwave processing for B4C ceramics were performed under flowing argon gas using the sintering system, which achieved 90 % of theoretical accuracy.
Abstract: Boron carbide (B4C) is one of advanced materials and is being used in a wide rage of applications. The unique feature of this material is its large neutron-absorbing cross-section. Some of its most prominent applications are controlling rods in nuclear reactors and radiation protection. 24 GHz microwave processing for B4C ceramics were performed under flowing argon gas using the sintering system. Sintering at the high temperature (up to 2200°C) was achieved using thermal insulation system consists of fiber-board, boron nitride powder, and boron nitride case. The sintered samples were achieved 90 % of theoretical.
25 citations
TL;DR: In this article, the first variants of both the electron optical system and the resonant cavity which have been designed aiming continuous frequency tunability in a broad frequency band are presented and discussed.
Abstract: In this paper we present some initial results from a conceptual design study focused on the development of a novel frequency tunable gyrotron for nuclear magnetic resonance (NMR) spectroscopy with signal enhancement based on the utilization of high field radiation and dynamic nuclear polarization (DNP) technique. The first variants of both the electron optical system and the resonant cavity which have been designed aiming continuous frequency tunability in a broad frequency band are presented and discussed. The selected method for frequency tunability is based on the excitation of higher order axial modes and smooth transition between them. It was selected after a critical examination of the known theoretical and practical results related to the frequency control in gyrotrons. It is believed that the current conceptual design is an appropriate basis for development of the next (optimized) design which will include also a detailed design of other components (mode converter, output window etc.) and magnetic circuit (superconducting magnet and supplementary solenoids) as well as for the overall mechanical design and fabrication of the prospective gyrotron.
21 citations
TL;DR: In this paper, the integration of an experimental 32 × 32 uncooled IR microbolometer array with an unplanar CMOS Readout Integrated Circuit (ROIC) is presented.
Abstract: In this paper, the integration of an experimental 32 × 32 uncooled IR microbolometer array with an unplanar CMOS Readout Integrated Circuit (ROIC) is presented. A vanadium oxide film fabricated by low temperature reactive ion beam sputtering is utilized as thermal-sensitive material in the bolometric detectors Before the integration, the unplanar ROIC for commercial use is first planarized by bisbenzocyclobutene film, then a electroless nickel-plating on ohmic contact areas is accomplished. Finally the bolometer array is fabricated using a micromachining process, which is completely compatible with CMOS technology. Measurements and calculations for the as-fabricated samples show that the responsivity of 1.4 × 104 V/W and the detectivity of 2.1 × 108cmHz1/2W−1 and a thermal response time of 10ms are obtained at a pulse bias of IV.
19 citations
TL;DR: In this article, a high efficiency mode converter of the ITER gyrotron operating mode into the Gaussian wave beam has been developed, which includes an irradiating waveguide with shallow deformation and profiled quasi-optical mirrors to increase the gaussian content.
Abstract: A high-efficiency mode converter of the ITER gyrotron operating mode into the Gaussian wave beam has been developed. It includes an irradiating waveguide with shallow deformation and profiled quasi-optical mirrors to increase the Gaussian content. Low-power tests were carried out with a TE25.10 mode exciter and a mode converter. A prototype of the short-pulsed 170 GHz gymtmn with the new converter was manufactured and tested. Diffraction losses measured inside the tube were less then 2% at the 1 MW power level. A high Gaussian mode content in the output beam has been also demonstrated.
19 citations
TL;DR: In this article, the authors measured the reflectance spectra in the near-infrared region between 800 and 2500 nm with a Varian CARY 500 spectrophotometer equipped with an integrated sphere to measure reflectance in solid samples.
Abstract: In the last few years, the production of kiwifruit (Actinidia deliciosa) has undergone a significant development with increasing international market. Therefore, the use of fast and non-destructive methods for ripening control is desirable. In this sense, NIRS technology (Near Infrared Spectroscopy) has proved to be very useful. The objectives of this work were to estimate the soluble solids content from NIRS technology and to evaluate the influence of the kiwifruit temperature on the NIR measures. A sample of 210 fruits was collected and stored for three months under cold conditions. The NIR measures were done at three kiwifruit temperatures (0.5°C, 10°C and 20°C) and the refractometric index was determined at the end of the experiment. The reflectance spectra in the near-infrared region between 800 and 2500 nm were measured with a Varian CARY 500 spectrophotometer equipped with an integrated sphere to measure reflectance in solid samples. The information has been analysed with Unscramble and SPSS statistical programs, which include a wide range of rapid data-processing applications and procedures, with a large number of options and graphic representations. The test performed for this study are PLS (partial least squares regression) and DA (discriminate analysis). Results showed: the validity of this technology to obtain a relationship between the NIRS and the soluble solids content, and differences on the wavelengths used in the calibrations, depending on the kiwifruit temperature.
TL;DR: Based on radar RHI (Range height indicator) measurements, cloud height has been deduced during the worst months (July-August) over Kolkata. Such cloud height results have been utilized to estimate cloud temperature as mentioned in this paper.
Abstract: Based on radar RHI (Range height indicator) measurements, cloud height has been deduced during the worst months (July–August) over Kolkata. Such cloud height results have been utilized to estimate cloud temperature. The attenuation of radiowave due to cloud in various probability levels has been determined in millimeter wave and microwave frequency bands. Such results on different probability levels are useful for satellite communication and remote sensing application over the aforesaid station in tropical India.
TL;DR: In this article, a unified first-principles approach is applied to the analysis of the interaction of gyrating electrons with electromagnetic waves with different characteristic impedance, and an approximate constant of motion is derived for the latter case from which the requirements for autoresonance can be satisfied easily in comparison to the TE modes.
Abstract: The electron cyclotron autoresonance is of both theoretical and practical interest for acceleration of charged particles and for generation of microwave radiation in various gyro-devices. In this paper a unified first-principles approach is applied to the analysis of the interaction of gyrating electrons with electromagnetic waves with different characteristic impedance. In contrast to the previous works that consider the underlying autoresonance integral only for the case of plane transverse waves and TE modes our analysis is applied also to TM modes. An approximate constant of motion is derived for the latter case from which it follows that the requirements for autoresonance can be satisfied easily in comparison to the TE modes. Some fundamental relations which follow from the analysis are discussed as well.
TL;DR: In this article, the authors studied the transmission problem of an electromagnetic pulse with given transversal structure passing through a waveguide converter from TM01 to TE11 mode of circular waveguide.
Abstract: We study a transmission problem of an electromagnetic pulse with given transversal structure passing through a waveguide converter from TM01 to TE11 mode of circular waveguide. Using FDTD numerical simulation method we have investigated mode structure of the pulse at the output of the converter and its dependence on pulse length at the input. Also we have obtained frequency characteristic by calculating Fourier response for a pulse with wide spectrum.
TL;DR: In this article, a 3mm Schottky diode mixer with high doping density (room-temperature) was used to achieve a noise temperature of 109 K at 20 K, which is much higher than the Teq of low doping density diode (cryogenic) diodes.
Abstract: The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes The measured equivalent noise temperature Teq of the diodes is 109 K at 20 K, which is much higher than the Teq of the low doping density (“cryogenic”) diodes In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier This is the lowest noise temperature ever reported for a Schottky diode mixer receiver The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used
TL;DR: In this paper, rain attenuation was calculated by using the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop size.
Abstract: The rain attenuation was calculated by using the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size. The results were compared with the recent measurements from 8 to 312.5 GHz at the rain rate R = 50mm/hr. Especially, the Weibull distribution has a good agreement with the measurements at 312.5 GHz (0.96 mm) in the submillimeter wavelength. Specific attenuation values from 1 to 1000 GHz were calculated for a rain temperature of −10°C, 0°C and 20°C by using the Weibull distribution.
TL;DR: In this article, a quasi-optical gap in the 31.75 mm diameter corrugated waveguide at frequency 84 GHz was proposed for low-loss miter bends.
Abstract: A systematic approach to design of low-loss miter bends and quasi-optical gaps in multi-mode waveguides is proposed. Several examples illustrate the approach. A mode filter based on a quasi-optical gap in the 31.75 mm diameter corrugated waveguide at frequency 84 GHz has been tested in low (mW) and high-power (200 kW, CW) experiments.
TL;DR: In this article, a new S-type IR integrated waveguide amplifiers, based on erbium-ytterbium co-doped phosphate glass integrated with medium thin film filter, is proposed.
Abstract: A new S-type of IR integrated waveguide amplifiers, based on erbium-ytterbium co-doped phosphate glass integrated with medium thin film filter, is proposed. The intrinsical gain spectrum of the proposed amplifier is obtained by solving rate and power propagation equations, a thin film filter flattening this intrinsical gain spectrum is designed by genetic algorithm, and fabricated. An average gain >10dB is obtained between 1530nm and 1560nm, and the average gain about 18dB between 1531nm and 1550nm with gain difference of <3dB is achieved.
TL;DR: In this paper, the authors extended the time modulation technique for the design of low sidelobe antenna arrays to millimeter-wave frequency band, and the element radiation patterns were taken into account in the analysis and design of time modulated linear arrays.
Abstract: In this paper, the time modulation technique for the design of low sidelobe antenna arrays is extended to millimeter-wave frequency band. Millimeter-wave rectangular waveguide is selected as the element radiators of linear antenna arrays, and the element radiation patterns are taken into account in the analysis and design of low sidelobe time modulated linear arrays. Two types of time modulation, namely, the time modulated variable aperture sizes (VAS) and unidirectional phase center motion (UPCM), are implemented in the design of low sidelobe millimeter waveguide linear arrays. It is observed that both the co-polarized and the cross-polarized components will experience the time modulation effect simultaneously. Many factors that affect the array performance are discussed.
TL;DR: In this article, a rigorous electromagnetic analysis of a circular waveguide loaded with axially periodic annular discs was developed in the fast-wave regime, considering finite axial disc thickness and taking into account the effect of higher order space harmonics in the disc-free region and higher order modal harmonics on the disc occupied region of the structure.
Abstract: A rigorous electromagnetic analysis of a circular waveguide loaded with axially periodic annular discs was developed in the fast-wave regime, considering finite axial disc thickness and taking into account the effect of higher order space harmonics in the disc-free region and higher order modal harmonics in the disc-occupied region of the structure. The quality of the disc-loaded circular waveguide was evaluated with respect to its azimuthal interaction impedance that has relevance to the gain of a gyrotron millimeter-wave amplifier (gyro-traveling-wave tube) in which such a loaded waveguide finds application as a wideband interaction structure. The results of electromagnetic analysis of the structure with respect to both the dispersion and azimuthal interaction impedance characteristics were validated against the commercially available code: high frequency structure simulator (HFSS). The analysis predicts that the value of the interaction impedance at a given frequency decreases with the increase of the disc hole radius and disc periodicity. The change of the axial disc thickness does not significantly change the value of the interaction impedance though it shifts the frequency range over which appreciable interaction impedance is obtained. Out of the three disc parameters, namely the disc hole radius, thickness and periodicity, the lattermost is most effective in controlling the value of the azimuthal interaction impedance. However, the passband of frequencies and the center frequency of the passband both decrease with the increase of the disc periodicity. Moreover, the disc periodicity that provides large azimuthal interaction impedance would in general be different from that giving the desired dispersion shape for wideband interaction in a gyro-TWT, suggesting a trade-off in the value of the disc periodicity to be chosen.
TL;DR: The simulated result that both matched input impedance and low noise temperature Tn can be achieved simultaneously over a wide bandwidth in the single-ended low noise amplifier is proved mathematically and is well interpreted.
Abstract: This paper analyzes different input-matching mechanisms used in designing the wide-band amplifiers in general, and the low noise amplifiers (LNA) in particular, and their corresponding noise impact. Among them, the most promising one is the reactive-feedback circuit configuration, which is a combination of high-frequency inductive feedback and low frequency capacitive feedback. In this paper the simulated result that both matched input impedance and low noise temperature Tn can be achieved simultaneously over a wide bandwidth in the single-ended low noise amplifier is proved mathematically and is well interpreted. This understanding of reactive feedback is crucial for the future development of ultra-wide-band low-noise amplifiers.
TL;DR: In this paper, the design and validation process for the profiled corrugated horn antennas, which feed the bolometer array of a cosmology experiment known as QUaD located at the South Pole, is reported.
Abstract: In this paper we report on the design and validation process for the profiled corrugated horn antennas, which feed the bolometer array of a cosmology experiment known as QUaD located at the South Pole. This is a cosmic background radiation polarization project, which demands precise knowledge and control of the optical coupling to the signal in order to map the feeble E- and B-polarization mode structure. The system will operate in two millimeter wavelength bands at 100 and 150 GHz. The imaging horn array collects the incoming signal via on-axis front-end optics and a Cassegrain telescope, with a cold stop in front of the array to terminate side-lobe structure at an edge taper of –20dB. The corrugated horn design process was undertaken using in-house analytical software tools, based on modal scattering, specially developed for millimeter -wave profiled horn antennas. An important part of the instrument development was the validation of the horn design, in particular to verify low edge taper levels and the required well-defined band edges. Suitable feed horn designs were measured and were found to be in excellent agreement with theoretical predictions.
TL;DR: In this paper, the authors employed the perturbational method to determine the propagation constants of higher-order modes in the coaxial waveguide, and the validity of the theoretical model is confirmed by comparison with results obtained using the high-frequency structure simulator.
Abstract: Overmoded coaxial waveguides have been used in coaxial gyrotrons as a key interaction structure. To achieve the required mode selectivity, the resistivity of the center conductor is properly chosen to damp unwanted modes. Considering attenuation due to conductor loss, this study employs the perturbational method to determine the propagation constants of higher-order modes in the coaxial waveguide. The validity of the theoretical model is confirmed by comparison with results obtained using the high-frequency structure simulator (HFSS). Moreover, the method proposed herein is applied to analyze the ohmic mode selection of the coaxial waveguide.
TL;DR: In this article, the authors presented preliminary ground-based lidar reflectance measurements on a variety of deciduous and coniferous trees under fully foliated conditions with a view towards tree species discrimination.
Abstract: There is growing interest in the use of lidar for remote sensing of vegetation owing to the emergence of reliable and rugged lasers and highly sensitive detectors. Lidar remote sensing has a distinct advantage over conventional techniques in vegetation remote sensing due to its capability for three-dimensional characterization of vegetative targets. The Multiwavelength Airborne Polarimetric Lidar (MAPL) system was developed primarily for vegetation remote sensing applications from an airborne platform of up to 1,000 -m altitude. The lidar system has full waveform capture and polarimetric measurement capability at two wavelengths in the near-infrared (1064 nm) and the green (532 nm) spectral regions. This study presents preliminary ground-based lidar reflectance measurements on a variety of deciduous and coniferous trees under fully foliated conditions with a view towards tree species discrimination. Variations in the reflectance characteristics of selected deciduous trees under unfoliated and fully foliated conditions were also investigated. Our study reveals distinct differences in the reflectance characteristics of various trees.
TL;DR: In this paper, a cascaded multilayer medium thin film filter structure is presented, which consists of some different filtering unit cells with different central wavelength and bandwidth, and each cell can suppress certain peak gain at a specific wavelength.
Abstract: This paper addresses in the design of thin film filter for IR broadband integrated photonic amplifiers. A cascaded multilayer medium thin film filter structure is presented. This proposed filter consists of some different filtering unit cells with different central wavelength and bandwidth, and each cell can suppress certain peak gain at a specific wavelength. The intrinsical gain spectrum of amplifier is obtained by solving a set of rate and power propagation equations with finite difference time-domain(FDTD)-based overlapping integral-Runge Kutter(RK) method. The effect of transmittance spectrum of the proposed cascaded multilayer medium thin film filter on flattening gain is discussed. The transmission function of the cascaded multilayer medium thin film filter is obtained. Finally, a real device is fabricated, it is shown that the design is valid.
TL;DR: In this article, the scattering of a plane electromagnetic wave from a Pruppacher-Pitter raindrop is treated using the Method of Auxiliary Sources (MAS) and compared with those taken from the open literature -in the form of real and imaginary part of the forward scattering amplitude -with excellent results.
Abstract: The combined effects of hydrometeor scattering and absorption result in significant power loss, for Earth-space microwave links operating at frequencies above 10GHz. With the increasing deployment of higher frequencies in commercial wireless networks, the accurate estimation of the specific rain attenuation is very significant for the reliable design of a radio communication system. In the present paper, the scattering of a plane electromagnetic wave from a Pruppacher-Pitter raindrop is treated using the Method of Auxiliary Sources (MAS). The obtained data are compared with those taken from the open literature -in the form of real and imaginary part of the forward scattering amplitude - with excellent results. Then, they are used for the numerical calculation of both the specific rain attenuation and the exceedance probability function, in the case of a hypothetical satellite link located in various climatic regions. The comparison with other models against experimental data has given very encouragingresults.
TL;DR: In this paper, the main factors affecting phase noise of MMW PLL frequency source are analyzed, and then a new method to estimate the phase noise is presented, which is based on the comparison of the phase noises of microwave phase-locked frequency source with phaselocked intermediate frequency in MMW phaselocked loop.
Abstract: Phase noise is an important index in evaluating the performance of millimeter wave (MMW) frequency source. Because of the high frequency, it is difficult to measure its phase noise directly. So it is very necessary to find new methods for estimating it effectively and easily. In this paper, the main factors affecting phase noise of MMW PLL frequency source are analyzed, and then a new method to estimate the phase noise is presented, which is based on the comparison of the phase noise of microwave phase-locked frequency source with phase-locked intermediate frequency in MMW phase-locked loop. In order to demonstrate the validity of this method of phase noise estimate, it is applied to estimate the phase noise of 95GHz double PLL frequency synthesizer. The result shows that the theoretical estimate value is well coincident with the experimental value.
TL;DR: An integrated 3mm-wave Schottky diode mixer and pseudomorphic high-electron-mobility transistor (PHEMT) IF amplifier with record noise performance at room temperature is described in this article.
Abstract: An integrated 3mm-wave Schottky diode mixer and pseudomorphic high-electron-mobility transistor (PHEMT) IF amplifier with record noise performance at room temperature is described. The design has shown the room-temperature double-sideband (DSB) receiver noise temperature TRDSB of 190 K at 100 GHz due to a very low conversion loss in the full-height waveguide mixer and an ultra-low noise of the PHEMT IF amplifier. The receiver noise temperature has been reduced by a factor of 1.5 in comparison with the best previously reported 3mm-wave Schottky diode mixer receiver.
TL;DR: In this article, a real-time gas Flow Control and Analysis (FCA) system was developed and successfully tested for its applications in Chemical Oxygen Iodine Laser (COIL).
Abstract: The composition of various gas effluents and their flow parameters viz. flow rate, pressure and Mach number are very crucial in determining the output of high power infrared gas lasers. PC based real time gas Flow Control and Analysis (FCA) System which is the heart of the high power infrared gas lasers such as CO2 Gas Dynamic Laser (10.6μm), Hydrogen Fluoride-Deuterium Fluoride (2.7–3.4μm) and Chemical Oxygen Iodine Laser (1.315μm) has been developed and successfully tested for its applications in Chemical Oxygen Iodine Laser (COIL). The system has been realized using the state of the art PCI bus based high-speed data processing electronics, a personal computer and electro-pneumatic components. The system has demonstrated its capability of controlling the flow rates in the range of 1-6500 lpm (in case of nitrogen) with a response time of 50 msec which is mainly limited by the response of the electro-pneumatic valves and pressure reducers used in the present system. The developed system also has the potential to monitor, estimate and display various flow parameters at critical locations of the laser system. More than 600 successful power runs of the COIL have been given using the developed FCA system.
TL;DR: In this paper, the dispersion equation in Cerenkov devices has been derived and analyzed numerically using the self-consistent linear theory, which can be applied to efficiently calculate all kinds of beam-wave interaction in different types of axisymmetric slow-wave structures (SWS) with arbitrary periodic profile.
Abstract: The “hot” dispersion equation in Cerenkov devices has been derived and analyzed numerically using the self-consistent linear theory. In principle, the linear analysis can be applied to efficiently calculating all kinds of beam-wave interaction in various Cerenkov devices composed of axisymmetric slow-wave structures (SWS) with arbitrary periodic profile. Then the results for Cerenkov devices with three typical SWS profiles are presented.