Search

Home gardens are ancient and widespread agroecosystems in the uplands of Vietnam. However, they are often ignored as an important part of traditional upland farming systems by scientists and extension workers due to their small size and the low economic value of the species. This chapter describes the structure and functions of home gardens in the local livelihoods of the Da Bac Tay ethnic minority in Vietnam's northern mountains. Despite their small areas surrounding the houses, Da Bac Tay's home gardens are a part of their habitation, units of high diversity, and high efficiency production and use of labor. This chapter also analyses the interaction between the home garden and the other components of the composite swiddening system to maintain its sustainability. We conclude that home gardens play an important role in the social, economic, and cultural life of the Da Bac Tay and should be considered as a means to reduce pressure on the forest and to maintain the sustainability of the composite swiddening system.

Recently, the CIE has adopted a range of 15 standard sky distributions covering the whole spectrum of usual skies found in nature. In a dense urban region, the external environment plays a significant role in daylighting designs. This paper studies an approach to calculating the average daylight factor for rooms facing heavily obstructed environments under overcast and non-overcast skies. The modelled vertical sky components under the various unobstructed and obstructed CIE Standard General Skies were determined. The performance of the proposed method was evaluated against the results obtained by computer simulations. The proposed approach provides a simple alternative for comparing daylighting designs for buildings facing different obstructed environments under various sky conditions.

Photovoltaic (PV) is one of the promising solar energy applications. Measured data can give the realistic performance of PV systems under actual operating environments for product selection and system design. This paper studies a grid-connected PV system installed in an institutional building. Technical data including available solar radiation and output energy generated were systematically recorded and analyzed. The performance of the PV system is elaborated in terms of energy, environmental and financial aspects. Feed-in-tariff (FIT) schemes with high electricity selling price can encourage the deployment of PV system. The monetary payback period (MPBP) for the PV system was computed to be 72.4 years when the electricity buying price is equal to the electricity selling price. If carbon trading was considered, the payback was shortened to 61.4 years. The embodied energy payback period (EEPBP) was estimated to be 8.9 years. The findings would be useful for planning grid-connected PV installations and applicable to other spaces with similar architectural layouts.

Past and future trend of electricity use for air conditioning in the entire commercial sector in subtropical climates using 1979–2008 measured meteorological data as well as predictions for 2009–2100 from a general circulation model (MIROC3.2-H) was investigated. Air conditioning consumption showed an increasing trend over the past 30 years from 1979 to 2008. Principal component analysis (PCA) of measured and predicted monthly mean dry-bulb temperature, wet-bulb temperature and global solar radiation was conducted to determine a new climatic index Z for 1979–2008 and future 92 years (2009–2100) based on two emissions scenarios B1 and A1B (low and medium forcing). Through regression analysis, electricity use in air conditioning for the 92-year period was estimated. For low forcing, average consumption in 2009–2038, 2039–2068 and 2069–2100 would be, respectively, 5.7%, 12.8% and 18.4% more than the 1979–2008 average, with a mean 12.5% increase for the entire 92-year period. Medium forcing showed a similar increasing trend, but 1–4% more. Standard deviations of the monthly air conditioning consumption were found to be smaller suggesting possible reduction in seasonal variations in future years.

Principal component analysis of prevailing weather conditions in subtropical Hong Kong was conducted, and a new climatic index Z (as a function of the dry-bulb temperature, wet-bulb temperature and global solar radiation) determined for past (1979–2008, measurements made at local meteorological station) and future (2009–2100, predictions from general circulation models) years. Multi-year (1979–2008) building energy simulations were carried out for a generic office building. It was found that Z exhibited monthly and seasonal variations similar to the simulated cooling/heating loads and building energy use. Regression models were developed to correlate the simulated monthly building cooling loads and total energy use with the corresponding Z. Error analysis indicated that annual building energy use from the regression models were very close to the simulated values; the difference was about 1%. Difference in individual monthly cooling load and energy use, however, could be up to 4%. It was also found that both the DOE-simulated results during 1979–2008 and the regression-predicted data during 2009–2100 indicated an increasing trend in annual cooling load and energy use and a gradual reduction in the already insignificant heating requirement in cooling-dominated office buildings in subtropical climates.

In a dense urban region in which high-rise buildings are packed inside limited land areas, the daylight components reflected from ground and surrounding buildings play significant roles in daylighting design. The natural light available in an interior strongly depends on the amount of daylight reaching the window facades. Lately we proposed a calculation procedure, presented in form of simple mathematical expressions and diagrams, to determine the daylight illuminance on a vertical plane under overcast skies. This paper extends the study to non-overcast sky conditions. The performance of the proposed method was evaluated by comparison with the daylight illuminance simulated by a lighting software, namely RADIANCE, and with measurements under real skies. It was found that the data estimated by the proposed method were in good agreement both with the values simulated by RADIANCE and with the measured results. The paper offers to architects and building engineers a useful tool for estimating the daylight illuminance and in particular for determining and assessing various daylighting schemes and concepts during design and construction stages.

An artificial neural network (ANN) model was developed for office buildings with daylighting for subtropical climates. A total of nine variables were used as the input parameters – four variables were related to the external weather conditions (daily average dry-bulb temperature, daily average wet-bulb temperature, daily global solar radiation and daily average clearness index), four for the building envelope designs (solar aperture, daylight aperture, overhang and side-fins projections), and the last variable was day type (i.e. weekdays, Saturdays and Sundays). There were four nodes at the output layer with the estimated daily electricity use for cooling, heating, electric lighting and total building as the output. Building energy simulation using EnergyPlus was conducted to generate daily building energy use database for the training and testing of ANNs. The Nash–Sutcliffe efficiency coefficient for the ANN modelled cooling, heating, electric lighting and total building electricity use was 0.994, 0.940, 0.993, and 0.996, respectively, indicating excellent predictive power. Error analysis showed that lighting electricity use had the smallest errors, from 0.2% under-estimation to 3.6% over-estimation, with the coefficient of variation of the root mean square error ranging from 3% to 5.6%.

Electric lighting is one of the major energy consuming items in many non-domestic buildings. Using appropriate energy-efficient light fittings with dimming controls and proper daylighting schemes can help reduce the electrical demand and contribute to visual comfort and green building development. This paper presents a study on the energy and lighting performances for energy-efficient fluorescent lamps associated with electronic ballasts and high frequency photoelectric dimming controls installed in a school building. Electricity expenditures and indoor illuminance levels for a workshop and a classroom employing high frequency dimming controls were analyzed. Simple prediction methods were used to illustrate the lighting savings. The findings provide the operational and performance information, which would be applicable to other spaces with similar building layouts and lighting schemes.

Past and future trends of human comfort in terms of heat and cold stresses under the local subtropical climates using measured meteorological data as well as predictions from general climate models were investigated. Summer discomfort showed an increasing trend (and winter discomfort a decreasing trend) over the past 41 years from 1968 to 2008. Monthly mean minimum and maximum temperatures and moisture content predictions from a general climate model (MIROC3.2-H) were used to determine summer and winter discomfort for future years (2009–2100) based on two emissions scenarios B1 and A1B (low and medium forcing). The 92-year (2009–2100) mean cold stress would be reduced from the 41-year (1968–2008) mean value of 8.7 to about three for both emissions scenarios. The 92-year mean heat stress would be 115.9 and 120.6 for B1 and A1B, respectively, representing 31.6% and 36.9% increase over the 1968–2008 long-term average of 88.1. These suggest that the already small winter heating requirement in subtropical Hong Kong would become even more insignificant in future years, whereas the increasing trend of summer discomfort would result in more cooling demand in the built environment.

The objective was to investigate whether energy use in buildings from simulation could be correlated with a new composite climatic index, which would account for the influences of major climatic variables such as temperature, humidity and solar radiation. Principal component analysis of prevailing weather conditions in sub-tropical Hong Kong was conducted, and a new climatic index Z determined. Multi-year (1979–2007) building energy simulations were carried out for a generic office building. It was found that Z exhibited daily and seasonal variations similar to the simulated cooling load and building energy use. Regression models were developed to correlate the simulated daily cooling load and building energy use with the corresponding daily Z. Error analysis indicated that annual building energy use from the regression models were very close to the simulated values; the difference was less than 2%. Difference in individual daily energy use, however, could be up to 6%. It was also found that both the simulated annual building energy use and the new climatic variable Z appeared to show an increasing trend during the 29-year period, indicating a subtle, but gradual change of climatic conditions that might affect energy use in buildings in future years.

Sustainability is the trend of the modern building designs, in which solar energy conversion systems and daylighting schemes are widely considered as the important building energy strategies to reduce the peak cooling and electrical demands, generate clean energy and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a renewable energy product producing electricity via solar cells and allowing natural light entering into the interior spaces for daylighting designs. The PV modules are effective in reducing the cooling demand, especially for the skylight atrium that often receives large solar heat gains. This paper studies the thermal and visual properties, energy performance, environmental and financial issues of such semi-transparent PV skylights. Field measurements including solar irradiance, daylight illuminance and electricity generated were carried out. Case studies based on a circulating atrium were conducted to evaluate the energy use, cooling requirements and monetary implications when the PV skylights together with the daylight-linked lighting controls were applied. The results indicated that such an integrated system could save the overall electricity expenditures and benefit to the environmental and financial aspects.

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.

Designing a building to integrate daylight requires an accurate estimation of the amount of available outdoor illuminance. The common method for predicting daylight has been the derivation of illuminance from the more widely measured solar irradiance using the luminous efficacy approach. Recently, the International Commission on Illumination (CIE) has adopted a range of 15 standard skies which cover the whole probable spectrum of skies in the world. This paper presents the work to model the luminous efficacy of diffuse component under the 15 CIE standard skies. Sky luminance distributions measured between 1999 and 2005 were used for the standard sky classifications. An approach to develop luminous efficacy for inclined surfaces was proposed. The predicted vertical outdoor illuminance data for the four cardinal planes (i.e., N, E, S and W) using the proposed luminous efficacy were evaluated against data measured in 2004. Statistical analysis indicated that the estimated daylight illuminance data give acceptable agreements with measured data for all vertical planes.

In subtropical Hong Kong, solar heat gain via glazing contributes to a significant proportion of the building envelope cooling load. The principal fenestration design includes eliminating direct sunlight and reducing cooling requirements. Daylighting is an effective approach to allow a flexible building facade design strategy, and to enhance an energy-efficient and green building development. This paper studies the lighting and cooling energy performances for a fully air-conditioned open-plan office when solar control films together with daylight-linked lighting controls are being used. Measurements were undertaken at two stages including the electricity expenditures for the office using photoelectric dimming controls only (first stage) and together with the solar control film coatings on the windows (second stage). Electric lighting and cooling energy consumption, transmitted daylight illuminance and solar radiation were systematically recorded and analysed. The measured data were also used for conducting and validating the building energy simulations. The findings showed that the solar film coatings coupled with lighting dimming controls cut down 21.2% electric lighting and 6.9% cooling energy consumption for the open-plan office.

Artificial lighting is one of the major electricity consuming items in many non-domestic buildings. Recently, there has been an increasing interest in incorporating daylight in architectural and building designs to reduce the electricity use and enhance greener building developments. This paper presents field measurements for a fully air conditioned open plan office using a photoelectric dimming system. Electric lighting load, indoor illuminance levels and daylight availability were systematically measured and analyzed. The general features and characteristics of the results such as electric lighting energy savings and transmitted daylight illuminance in the forms of frequency distributions and cumulative frequency distributions are presented. Daylighting theories and regression models have been developed and discussed. It has been found that energy savings in electric lighting were over 30% using the high frequency dimming controls. The results from the study would be useful and applicable to other office spaces with similar architectural layouts and daylight linked lighting control systems.

A 193 nm excimer laser and a custom fabricated cylindrical lens system is used to produce a plasma sheet of 8 cm×30 cm×0.4 cm in tetrakis(dimethylamino)ethylene (TMAE), a low ionization energy organic gas. Plasma density variation due to photon absorption is studied by scanning the filling pressure of TMAE between 12 and 150 mTorr. A high density (n≥2.0×1013 cm−3), low temperature (Te≊0.8 eV) plasma sheet of 4 mm thickness is obtained with less than 50% spatial density variation over the 30 cm axial length. Charge recombination is found to be the dominant process for t≤1.2 μs with the plasma diffusion playing a perturbational role. A one‐dimensional plasma model is utilized to model the experimental plasma data by treating the diffusion as a perturbation. This study shows that the recombination coefficient is 1.8±0.1×10−7 cm3 s−1 and the diffusion coefficient is 2.8±0.4×104 cm2 s−1. The plasma sheet has attractive properties for a microwave agile mirror.

Experiments with plasmas having nearly equal concentrations of deuterium and tritium have been carried out on TFTR. To date (September 1995), the maximum fusion power has been 10.7 MW, using 39.5 MW of neutral beam heating, in a supershot discharge and 6.7 MW in a high beta P discharge following a current ramp-down. The fusion power density in the core of the plasma has reached 2.8 MW/m3, exceeding that expected in the International Thermonuclear Experimental Reactor (ITER). The energy confinement time tau E is observed to increase in DT, relative to D plasmas, by 20% and the n1(0).T1(0). tau E product by 55%. The improvement in thermal confinement is caused primarily by a decrease in ion heat conductivity in both supershot and limiter H mode discharges. Extensive lithium pellet injection increased the confinement time to 0.27 s and enabled higher current operation in both supershot and high beta P discharges. First measurements of the confined alpha particles have been performed and found to be in good agreement with TRANSP simulations assuming classical confinement. Measurements of the alpha ash profile have been compared with simulations using particle transport coefficients from helium gas puffing experiments. The loss of energetic alpha particles to a detector at the bottom of the vessel is well described by the first-orbit loss mechanism. No loss due to alpha particle driven instabilities has yet been observed. ICRF heating of a DT plasma, using the second harmonic of tritium, has been demonstrated. DT experiments on TFTR will continue both to explore the physics underlying the ITER design and to examine some of the physics issues associated with an advanced tokamak reactor

The deuterium-tritium (D-T) experimental program on the Tokamak Fusion Test Reactor (TFTR) is underway and routine tritium operations have been established. The technology upgrades made to the TFTR facility have been demonstrated to be sufficient for supporting both operations and maintenance for an extended D-T campaign. To date fusion power has been increased to {approximately}9 MW and several physics results of importance to the D-T reactor regime have been obtained: electron temperature, ion temperature, and plasma stored energy all increase substantially in the D-T regime relative to the D-D regime at the same neutral beam power and comparable limiter conditioning; possible alpha electron heating is indicated and energy confinement improvement with average ion mass is observed; and alpha particle losses appear to be classical with no evidence of TAE mode activity up to the P{sub FUS} {approximately}6 MW level. Instability in the TAE mode frequency range has been observed at P{sub FUS} > 7 MW and its effect on performance is under investigation. Preparations are underway to enhance the alpha particle density further by increasing fusion power and by extending the neutral beam pulse length to permit alpha particle effects of relevance to the ITER regime to be more fullymore » explored.« less

Broadband microwave propagation and absorption processes and backscatter from objects immersed in a magnetized, finite, warm plasma column is addressed. In particular, the propagation, absorption, and backscatter of electron cyclotron waves are measured and compared with bounded vacuum hot plasma wave propagation, absorption, and ray tracing theory. The nonreciprocal nature of the transmission and absorption in an anisotropic plasma is measured. A homodyne technique which isolates the scattering from a single object in the plasma from the scattering from all other objects in the plasma and the walls of the containment device is developed and utilized. The range of absorption frequencies and nonreciprocity of the transmission signal are shown to be well correlated with wave trajectories in the associated regions of the Clemmow-Mullaly-Allis (CMA) diagram. It is shown that quasi-parallel propagation of electron cyclotron waves near resonance is present and that the transverse effects of wavenumber on propagation in the cylindrical plasma are small. >

The paper presents a study of the effects of a simulated L- to H-mode transition for the proposed BPX (Burning Plasma Experiment) device on the coupling of a recessed coil antenna in the ion cyclotron range of frequencies. Two computer codes are used: ANTIMP, a code developed by the authors, which uses a Runge-Kutta method of solution, and a finite element code, developed by Brambilla, which has been modified to examine fourfeed antenna coils. The radiation resistance is calculated for antenna parameters consistent with a design proposed by the Oak Ridge National Laboratory. Both finite cavity size and finite phase velocity along the current straps are modelled. The plasma density is simulated using both piecewise linear profiles and parabolic profiles. For anticipated BPX values of the density gradient at the separatrix, the radiation resistance decreases by a factor of two to three during an L- to H-mode transition. The reduction of the value of the radiation resistance due to finite phase velocity can be minimized by using a four-feeder scheme.

We study the effects of an L-to H-mode transition in a tokamak on the loading of fast wave launchers in the Ion Cyclotron Range of Frequencies. For analytical simplicity, a dielectric-filled waveguide is chosen for analysis. However, other apertures or coils can readily be accommodated within the formalism. The H-mode density at the edge is modeled as a pedestal followed by a region of Gaussian variation. We calculate the waveguide reflection coefficient, the equivalent surface plasma impedance and the electric field profile at the aperture, for conditions appropriate to CIT (Compact Ignition Torus). It is concluded that an L- to H-mode transition can impose substantial loading variations on the launcher system. These variations can be matched by appropriate fast response tuner systems, similar to those used for coil antennas.

A prior requirement to the design of any solar-based conversion systems is the knowledge of optimum orientation and tilt surface at which peak solar energy can be collected. In many parts of the world, however, the solar radiation data for the surfaces of interest are not always available. This paper presents a numerical approach to calculate the solar radiation on sloped planes by integrating the measured sky radiance distributions. The annual total solar yield at different sloped surfaces facing various orientations and monthly solar radiations at the optimal tilt surface and three vertical planes facing east, south, and west were determined. The energy outputs and efficiencies were simulated using a computer package. The environmental benefits in terms of greenhouse gases reductions and cost implications were also considered. The findings provide technical information for engineers to design and evaluate photovoltaic (PV) systems which could contribute to the environmental, energy, and economic aspects.

An excimer-laser ({lambda} = 193 nm) produced plasma in an organic gas (TMAE) has been generated and studied. These studies have determined the ion-electron recombination coefficient and the photon absorption cross-section, of the neutral gas. The dependences of wave transmission, reflection and absorption on plasma density are obtained. A new optical system with an array of cylindrical XUV coated lenses has been implemented to form a plasma sheet to study its usage as agile mirror microwave reflector. The lens system expands the incident laser beam in X direction and compresses it in Y direction to form a sheet beam. The expanded beam then passes through a vacuum chamber filled with TMAE at 50--500 nTorr to produce the plasma sheet. Space-time measurements of the plasma density and temperature as measured by a Langmuir probe are presented. XUV optical measurements of the laser beam as measured by a photodiode are presented. Initial experiments have generated a plasma sheet of 5--10 mm x 11 cm with peak plasma density of 5 {times} 10{sup 13} cm{sup {minus}3}. A microwave source will be utilized to study the agile mirror character of the plasma sheet. Modeling of the microwave reflection from the plasma profile will alsomore » be discussed.« less

The authors summarize an approach to developing a quantitative model for predicting the performance impact of a decision aid. This approach emerged from research in team decision making. The approach predicts combined user/decision aid performance. The approach to developing a predictive performance model for a decision aid is to first to characterize a decision aid use strategy, and then to use this strategy to determine the function for predicting combined user/decision aid performance. Examples provide some simple illustrations of this approach. >

Summary form only given. A Vacuum Ultra-Violet (VUV) laser pulse is used to create a plasma sheet in a low-ionization-energy organic gas. Microwaves from a highly directive X-band horn antenna impinge on the sheet where they are reflected. A bi-static antenna system is used for transmitting and receiving the microwave radiation. Both heterodyne and homodyne detection systems are investigated for maximum sensitivity. Reflected signals are measured for amplitude and phase analysis. Comparable amplitude and phase shifts are noted when compared to an aluminum conducting sheet placed in the same position as the plasma. The working gas is tetrakis(dimethylamino)ethylene (TMAE) with an ionization energy of 5.36 eV. The ionizing source is a VUV excimer laser operating at 193 nanometers (6.4 eV). The laser and plasma properties are diagnosed by an optical detection system and by Langmuir probes. The laser beam is transformed into a sheet using VUV coated Suprasil lenses (96% transmission efficiency). A plasma sheet with a peak density of 2.5/spl times/10/sup 13/ cm/sup -3/ and T/sub e/=0.8 eV is formed. Additional measurements of transmitted signals are utilized to determine plasma density and collision frequency. A computer model of the microwave transmission and reflection levels has been developed to optimize reflected signal levels as a function of density and thickness and to interpret experimental results. Comparison between the experimental results and the model show that this system is attractive for use as a microwave reflector.

Summary form only given. Agile microwave reflectors are of interest as potential replacements for large phased arrays on mobile crafts. Microwave reflection from an VUV(/spl lambda/=193 nm) excimer laser produced plasma (W=20 mJ, /spl tau/=17 ns) in an organic gas (TMAE: tetrakis-dimethylamino-ethylene) contained in a 22 mm/spl times/7 mm rectangular column, has been demonstrated. This work investigates the reflection of X-band microwaves at normal and oblique incidences by a planar TMAE sheet of dimensions: 9 cm W/spl times/2-7 mm H/spl times/10-20 cm L, produced by the same excimer laser. Suprasil VUV coated (96% transparent) lenses are used to generate the sheet laser beam profile. Both triple probes and reference probes are used to determine the 3-D laser produced plasma density and temperature profiles, at TMAE neutral pressures in the 25-150 mTorr range. The plasma diffusion during its lifetime is very small. Densities and temperatures in the ranges of n=5/spl times/10/sup 12/-2/spl times/10/sup 13/ cm/sup -3/ and T/sub e/=0.5-0.7 eV are obtained. An examination of the microwave reflection is carried out using X-band horns and rectangular guide apertures. The amplitude and phase of the transmitted and reflected microwave signals are measured using both homodyne and heterodyne systems with hybrid-tee mixers. A time history of the plasma and temperature density is obtained with Langmuir probes and compared with. a measurement based on microwave transmission through the plasma. Reflected and transmitted signals are compared with those from an aluminum sheet of the same dimensions as the plasma. Future plans for the agile mirror reflector and absorber are discussed.

Summary form only given, as follows. A large plasma sheet is created by a 193 nm laser ionizing a low ionization potential molecule tetrakis-(dimethylamino)ethylene (TMAE). The plasma density is diagnosed by a fast response single Langmuir probe, and special features of the probe measurements at early times in the laser produced plasma are discussed. On microsecond time scales, the plasma decay is dominated by a two-body recombination process, and other plasma decay processes, such as plasma diffusion, electron attachment, three-body recombination with either another molecule or an electron as the third body, can be neglected. The initial plasma densities vary for different experimental conditions, but all the density traces at later times approach a same limit, which is only sensitive to the two-body recombination coefficient. Based on plasma density measurements, a dielectric model is developed to calculate the properties of microwave reflection from the plasma sheet. The critical reflection angles for different plasma densities, as well as the polarization effects on the microwave reflection are discussed. The calculations of microwave reflection from the plasma density measurements agree well with those obtained by direct microwave measurements.

Summary form only. An excimer-laser (/spl lambda/=193 nm, r=17 nS, E=20 mJ) along with a cylindrical lens system is utilized to produce a sheet plasma, in an organic gas (TMAE). The plasma has a peak density of 3.5/spl times/10/sup 13/ cm/sup -3/ and a "sheet" like profile of 0.2-0.7 cm/spl times/8 cm/spl times/20 cm. The effect of the lens system on the plasma, sheet thickness is examined. The triple probe measured plasma temperature (T/sub e//spl ap/1 eV) agrees with the postulation of single-photon absorption-ionization process. The plasma density spatial decay along the laser beam, which is associated with TMAE photon absorption length, is measured. The absorption length is found to be a function of base pressure of the neutral working gas. We have obtained an optimal window of TMAE base pressure at 50-150 mTorr. Within this optimal pressure range a plasma formation can have a long absorption length (L/sub a//spl ges/10 cm), relatively high plasma density (n/sub e//spl ges/5/spl times/10/sup 12/ cm/sup -3/), and lifetime of 5 /spl mu/s. A 1-D plasma diffusion model is proposed and solved both analytically and numerically. Comparison of the modeling and the measured results yields accurate values for the plasma diffusion and recombination coefficients.

Summary form only given. Agile microwave reflectors are of interest as a potential replacement of phased arrays in radar applications. Microwave reflection from an XUV (/spl lambda/=193 nm) excimer laser (Wmax=20 mJ, r=17 ns) produced rectangular Tetrakis(dimethyl-amino)ethylene (TMAE) plasma column of dimensions 2.2 cm wide, 0.7 cm thick and up to 40 cm long has been demonstrated. This work demonstrates reflection of X-band microwaves at normal incidence by a planar TMAE plasma sheet of dimensions 7.8 cm wide, 0.7 cm thick and up to 40 cm long generated with the same excimer laser. Suprasil XUV lenses coated for 98% transparency at /spl lambda/=193 nm are used to generate the sheet beam profile. The plasma is in the far field of an X-band rectangular aperture antenna used to launch the microwaves. Amplitude and phase measurements of the reflected and transmitted microwave signal is achieved with microwave interferometers utilizing magic-tees. Three dimensional plasma density and temperature profiles as a function of time are obtained with Langmuir probes and compared with a measurement based on microwave transmission through the plasma. Langmuir triple probe measurements indicate that the peak plasma temperature is about 1 eV and densities are on the order of 10/sup 13/ cm/sup -3/.

Summary form only given, as follows. This work examines fundamental deuterium and second harmonic tritium heating in ITER and TFTR. The fundamental heating scenario is (D)T in an ITER-like plasma with baseline parameters (R/sub major/=6 m; r/sub minor/=2.2 m; B/sub minor/=4.85 T; n/sub e/=9.0/spl times/10/sup 19/ m/sup -3/; T/sub e/=10-15 keV). The enhanced fusion reactivity resulting from the non-Maxwellian deuterium population (given by Stix's quasi-linear formalism) has been evaluated numerically. The absorption and reflection coefficients for the fast wave are calculated using the full-wave code XWAVE. For ITER, we find that the presence of the (D-T) hybrid resonance can give rise to a substantial enhancement of the local a particle absorbed power density and significant reflection. When the hybrid resonance layer is moved to the magnetic axis, the single-pass alpha power absorption coefficient can reach up to 70% (with greatly reduced reflection) for parameters corresponding to an advanced ITER design. The behavior of the distribution function of the alphas has also been investigated using FPPRF, a bounce-averaged Fokker-Planck code. These results can be relevant to a possible alpha current drive scheme in ITER-class machines. The second harmonic tritium heating scenario is a D-T plasma with hot D and T beams, and small concentrations of He/sup 3/ and /spl alpha/. The plasma parameters have been chosen from TRANSP calculations of recent D-T runs in TFTR, and the analysis is carried out with SEMAL, a global full-wave code based on a finite-element method. We find that the absorption by fusion alphas can be significant for large parallel wave numbers.

Three campaigns, prior to July 1994, attempted to increase the fusion power in DT plasmas on the Tokamak Fusion Test Reactor (TFTR). The first campaign was dedicated to obtaining >5 MW of fusion power while avoiding MHD events similar to the JET X-event. The second was aimed at producing maximum fusion power irrespective of proximity to MHD limits, and achieved 9 MW limited by a disruption. The third campaign increased the energy confinement time using lithium pellet conditioning while raising the ratio of alpha heating to beam heating.

Summary form only given. Plasma generation in an organic molecular gas through a one-photon ionization process is studied. A 1-D model is derived to describe the photon flux flow and electron density evolution. Plasmas are generated in a low-ionization potential gas, tetrakis (dimethylamino) ethylene (TMAE) vapor, through a one-photon ionization process by an ultraviolet laser beam (E - 10 mJ, /spl tau/ - 17 ns) at 193 nm. A new method is used to measure the 193-nm ultraviolet (UV) photon absorption cross-section in TMAE. It is determined to be 1.1 /spl plusmn/ 0.3 /spl times/ 10/sup -7/ cm/sup 2/ from the axial profile of electron density. A high-density sharp boundary plasma sheet produced by a UV sheet beam obtained from the laser output through an optical system is examined. The microwave reflection from the plasma sheet is examined, and the potential application of a TMAE plasma as a mirror for microwave reflections is discussed. When TMAE is ionized in a higher-pressure background gas (argon/helium), a highly collisional, diffuse-boundary plasma can be produced.

Summary form only given. Measurements and analysis of the absorption, reflection, and scattering of electromagnetic waves due to electron cyclotron absorption zones and the presence of modulated scatterers in a plasma are presented. Measurements using a modulated homodyne detection system have been made that are sensitive to the backscatter from a movable probe in the plasma. The phase sensitive system is used to measure the local k-spectrum in the inhomogeneous plasma and is compared with WKB (Wentzel-Kramers-Brillouin) theory. A 12-cm-diameter by 2-m laboratory plasma is produced by a 2.45-GHz microwave source. Wideband wave absorption of 30-50 dB due to the electron cyclotron resonance zone in the 1.5-3.0 GHz range is measured. Experiments examining the microwave scattering frequency sensitivity of modulation-launched magnetoacoustic modes from a ceramic encapsulated PIN diode and from a disc Langmuir probe scatterer have also been performed.

Summary form only given. Measurements and analysis of the absorption, reflection, and scattering of electromagnetic waves due to electron cyclotron resonance zones and the presence of scatterers in the plasma were carried out. The 12-cm-diameter by 2-m laboratory plasma was produced by a 2.45-GHz microwave source in a local mirror field, with wave measurements carried out in a larger mirror region. The plasma density that could be created was in the range of 5t109 to 5t1011/cm3 with electron temperatures in the 3-6-eV range and 0.5-2-kG magnetic fields. Wave absorption measurements of 25-50 dB due to the electron cyclotron resonance zone in the 1.5-3.0-GHz range were performed. A modulated homodyne detection system that isolates the backscatter from a single object in the plasma and suppresses the scattering from the walls. probes, and other background was constructed. This system was used to measure the shielding produced by the plasma, including the shielding by cyclotron resonance. The effect of collisional absorption for particular density profiles in weakly magnetized plasmas was analyzed to determine their effect on reflectivity. For collisional. low-magnetic-field plasma conditions comparable to those that can be obtained in the present experiments, the electromagnetic wave reflectivity was calculated using various Epstein profiles

In reactor situations, a waveguide may have certain advantages (such as power handling capability and structural rigidity) over loop antennas as fast wave launchers in tokamaks. We carry out a numerical analysis of a dielectric‐filled rectangular waveguide, using a formalim that gives the wave reflection coefficient from the plasma (or the equivalent plasma impedance), once the plasma surface admittance tensor and the eigenmodes of the unloaded launcher are known. In the context of a slab model, we obtain the plasma surface admittance tensor by solving the wave differential equations in a cold plasma, assuming a radiation condition from inside the plasma. The eigenfunctions of the rectangular waveguide are readily written down. For the vacuum folded waveguide, semi‐analytical expressions for the TE mode eigenfunctions hasve been obtained by a Ritz variational method. Some problems concerning the calculation of the reflection coefficient for a folded waveguide are discussed.

We present an analysis of a rectangular dielectric‐filled waveguide, suitable for ICRF heating. To simulate the H‐mode, we take the edge plasma to consist of a pedestal of variable length followed by a region with either a parabolic or a gaussian variation. We present numerical results for the waveguide reflection coefficient, the equivalent surface plasma impedance and the electric field profile at the aperture, for a wide range of edge plasma conditions. A dielectric‐filled rectangular waveguide launcher has been designed, fabricated and tested for the ICRF wave coupling. Our theoretical analyses and measurements over the 60–130 MHz range indicate that a very high power coupling efficiency (≥90%) can be obtained for a matched launcher with appropriate tuning of the noncontacting sliding short. An input reflection coefficient model has been developed for a matched or plasma‐loaded waveguide launcher and compared with measurements.

The specific heat of Mn 0.27 Co 0.73 Cl 2 ·6H 2 O has been measured in the temperature range 1.4 K to 4.4 K. A λ-type anomaly was observed at 2.10 K, corresponding to an antiferromagnetic-paramagnetic transition. Approximately 50% of the entropy is recovered above the Neel temperature. Using the specific heat data, a calculated sublattice magnetization was obtained and compared to several statistical models.