Few Tens Of Watts Research Articles

Design of Stray Radiation Sensor for ITER ECE Diagnostic

The Electron Cyclotron Emission (ECE) diagnostic has a primary role in the measurement of electron temperature profile and electron temperature fluctuations in ITER. This diagnostic shall be exposed to significant power due to unabsorbed Electron Cyclotron Heating (ECH) power in the plasma. The expected stray power loads could be a few tens of watts, and therefore, the protection of millimetre wave components is one of the design challenges of ITER ECE diagnostic. This protection system includes sensors, a band stop notch filter, and a shutter to stop the RF stray radiation from being incident on the sensitive components. The sensors will be positioned along the ECE transmission line, and shall be used for real-time power monitoring of the stray radiation. Here, we describe a novel design of a sensor for monitoring the stray radiation power. This sensor is a Schottky Diode rectenna, known for high-power and high-speed millimetre wave detection capability. It consists of a 2x2 microstrip patch antenna array, a matching circuit, a diode, and a low pass filter. The antenna array is designed analytically and optimized in CST Microwave Studio, for wide reception angle, high gain, and low side lobe levels. Furthermore, the rectifying circuit is optimized using Agilent Advanced Design System (ADS) software to get better rectification and impedance matching of the signal, thereby improving its detection sensitivity. The ADS simulation results show that the detection sensitivity is about 1000V/W for input power of -30 dBm at 170 GHz, thereby achieving the required performance of the sensor.

Challenges in the Numerical Analysis of Centrifugal Pumps¨: Energetic, Cavitation and Dynamic Characteristics

Pumps are energetic devices that are present in a wide range of industries. Their installed power varies from a few tens of watts up to hundreds of megawatts. As the energy consumption is connected with global warming and climate change, the development of pumps that have good characteristics is very important. Theoretical and experimental methods have long been utilized in the development of pumps, but recently much research has been carried out with the help of Computational Fluid Dynamics (CFD) analysis. Certain numerical analyses can be of high quality and accurate, but special operational phenomena still occur, where special attention is required when performing analysis. This category includes operating regimes outside the Best Efficiency Point (BEP), the formation of inlet recirculation, cavitation, and the influence of wall roughness on all the above characteristics. The current paper presents the main problems that developers face when numerically analyzing the above-mentioned special operating regimes. Both numerical and experimental results are considered.

Modelling of a miniature mid-IR thermo-optic spectrometer on chip based on a GaAs/In[formula omitted]Ga[formula omitted]P waveguide platform

Spectrometers based on integrated optical waveguides, as opposed to free space optics, provide many advantages including robustness, compactness, and low cost, combined with alignment-free and low-power operation. Interest in such a chip-based approach for integrated spectrometers is growing, but the integrated spectrometers demonstrated so far have largely been limited to operation at wavelengths up to about 5μm due to intrinsic material absorption. In this work, we design and model an on-chip thermo-optically tuneable spectrometer based on a novel waveguide material platform consisting of GaAs (core) on InGaP (cladding), with potential to operate in the wavelength range between 1 and 17μm to fully cover the Mid-IR molecular fingerprint region. The strong thermo-optic effect exhibited by both of these materials makes the platform a very promising candidate for on-chip spectroscopy. A series of simulations were performed to predict the optical and thermal properties of the device. We show that with the proper optical and thermal optimisation of the platform and by using an interferometer with spiralled waveguides of 60 mm length, the device can effectively achieve a resolution of 10 cm−1 with a maximum temperature excursion of about 83 K and at the cost of a few tens of Watts of power.

Modeling and Validation of Moving Coil Actuated Valve for Digital Displacement Machines

This paper concerns a novel moving coil actuator integrated with a high-performance seat valve for use in digital displacement machines (DDM), which is an emerging fluid power technology that sets strict actuator requirements in order to get a high energy conversion efficiency. Hence, the mechanical switching time must be in the millisecond range and the actuator power consumption must be in range of few tens of watts. The objectives are twofold: First, establish a proof-of-concept for the integrated actuator/valve that relies on several principles and mechanisms new or uncommon in fluid power applications. Second, formulate and validate a transient numerical model describing the actuator/valve. A coupled simulation model is established to predict the switching performance in which transient electromagnetic finite-element-analysis with dynamic remeshing is coupled to a set of ordinary differential equations describing the motion dynamics. In this way, the movement induced hydromechanical fluid forces caused by rapid acceleration of the valve plunger is coupled with the electromagnetic dynamics. The proposed model is compared rigorously against measurements obtained from a series of experiments based on a fully operational valve prototype. Comparisons of, e.g., transient flux density, current, and plunger position, show that the model describes both the actuator and the valve motion very well. Finally, results are presented when testing the prototype valve in fully operational DDM to establish proof-of-concept for the proposed valve concept. The actuator/valve is shown to be capable of rapid switching in less than 4 ms, while only consuming approximately 45 W corresponding to 0.7% of the machine output power.

Intracerebrovascular enzyme replacement therapy for CLN2 disease: A collaborative, multi-disciplinary approach

This chapter briefly reviews the different applications of natural circulation systems (NCSs) in various industries. Closed-loop NCSs are extensively used in solar water heaters, geothermal, fossil-fueled, and nuclear power plants. In addition, these systems are used in component-cooling applications such as transformers, electronic devices such as computer chips, and gas turbines. Although NCSs are mainly employed as heat transport devices, they can be engineered for noncooling applications such as passive controls, liquid fins, and study of low-velocity corrosion and deterministic chaos. Examples of open-loop natural circulation applications include solar chimneys, buoyancy pumps, air lift pumps, and building ventilation. The largest applications of NCSs are possibly in the chemical process industries. However, the highest power operating NCSs can be found in fossil-fueled power plants. The ESBWR (Economic Simplified Boiling Water Reactor) is the highest power (4500 MW) NCS designed so far. Mini loops with heat transport capability of the order of a few tens of Watts also can be found in the electronics industry.Some of the emerging applications of NCSs are in passive cooling of aircraft, vehicles, building ventilation, and solar thermal power plants. Due to the energy-saving potential of natural circulation, its application is increasing in various industry sectors. Natural circulation applications in electronics device cooling, solar thermal power plants, and residential buildings are expected to increase in the near future. In addition, its passive functioning without operator action or signal is important for enhanced safety and reliability of nuclear reactors, increasing their applications in the nuclear field.

Periodically Allocated Reentrant Cavity Klystron

A novel klystron topology is proposed to overcome the frequency limits of conventional klystrons. In contrast to the conventional klystron approach, where the distance between the cavities placed along the drift tube is a function of the plasma frequency wavelength, the new configuration exploits the interaction property of a sequence of numerous cavities allocated at fixed short distance along the drift tube. The remarkable advantage is to obtain good performance by the use of cavities with low R/Q, as in the case of high-frequency and high-order mode operation. A frequency operation up to 136 GHz with 20-dB gain and an output power up to a few tens of watts are demonstrated. The promising performance of the periodically allocated reentrant cavity klystron makes it attractive for millimeter-wave applications.

Frequency scaling with miniature COmpact MIcrowave and Coaxial ion sources

We will present recent basic developments about possible extension of the COMIC (for COmpact MIcrowave and Coaxial) devices up to 5.8 GHz in place of the present 2.45 GHz operation [P. Sortais, T. Lamy, J. Médard, J. Angot, L. Latrasse, and T. Thuillier, Rev. Sci. Instrum. 81, 02B314 (2010)]. New applications associating multiple COMIC devices for thin film deposition will be described and we will explain why an increase of the current density delivered by each individual ion source could lead to the increase of the deposition rate. For this purpose, we will present results of about two devices working at 5.8 GHz. The first one is a tiny ion source, the world smallest microwave ion source, exactly similar to COMIC but operating at 5.8 GHz with a quarter wave cavity structure and a few watts microwave power consumption. We will show that the frequency scaling effect is effective inside such small machines. The second one is a more ambitious ion source designed around a three quarter wave structure that works with a few tens of watts at 5.8 GHz.

The Human Brain Project and neuromorphic computing.

Understanding how the brain manages billions of processing units connected via kilometers of fibers and trillions of synapses, while consuming a few tens of Watts could provide the key to a completely new category of hardware (neuromorphic computing systems). In order to achieve this, a paradigm shift for computing as a whole is needed, which will see it moving away from current "bit precise" computing models and towards new techniques that exploit the stochastic behavior of simple, reliable, very fast, lowpower computing devices embedded in intensely recursive architectures. In this paper we summarize how these objectives will be pursued in the Human Brain Project.

Manipulating Dust Charge Using Ultraviolet Light in a Complex Plasma

Making use of a 1-D particle-in-cell plus Monte Carlo code, which includes the scattering and collection of plasma particles on dust immersed in the plasma, we study the effect of photodetachment by ultraviolet (UV) photons in a radio frequency dusty argon plasma. This is done by adding a UV source in the model, which results in a UV flux entering the plasma from the left side. The dust charge is reduced for dust clouds consisting of 5- mum particles at a dust density relevant for both experiments and plasma applications. Using UV photons with energies above the work function, but below the ionization threshold, at fluxes of a few tens of watts per square meter, provides an interesting tool to control the dust charge in such plasmas. This could result in a way to control the dust particle coagulation or dust transport. For very high dust densities, the dust charge is not reduced by the incident UV photons

Aligned carbon nanotubes/fibers for applications in vacuum microwave amplifiers

Most long-range telecommunication systems are based upon microwave links. The transmitters use microwave amplifiers which in the very near future will be required to work at up to 30–100GHz with output power in the region of a few tens of watts. Carbon nanotubes (CNTs), which exhibit extraordinary field emission properties because of their high electrical conductivity, ideal high aspect ratio whisker-like shape for geometrical field enhancement, and remarkable thermal stability, can be used as the emitter in such applications. This article will describe the plasma enhanced chemical vapor deposition growth of vertically aligned carbon nanotubes, and how well controlled arrays of such structures can be grown. We will also describe how high current densities of ∼1A∕cm2, under direct current and 1.5GHz direct modulation, can be obtained from CNT cathodes. These CNT cold cathodes offer considerable weight and size savings over conventional hot cathodes used in microwave applications (e.g., SATCOM, radar).

Cylindrical Metal Wire Surface Coating with Multiwalled Carbon Nanotubes by an Atmospheric-Pressure Microplasma CVD Technique

A simple technique to coat the surface of a cylindrical tungsten wire with multiwalled (MW) carbon nanotubes (CNTs) has been developed. The coating was deposited by CVD using an atmospheric-pressure microplasma generated in a quartz capillary by a few tens of watts of UHF power. The deposition and growth manner of the MWCNTs were controlled by the method of passage of CH4 and vaporized ferrocene gases. When the two gases were supplied simultaneously, the deposited surface of the tungsten wire contained tangles of MWCNTs. However, aligned MWCNTs were formed when vaporized ferrocene was fed first followed by CH4. In this process, the growth rate of MWCNTs was relatively high compared with conventional plasma-enhanced CVD. This is a new method to prepare MWCNTs efficiently with low energy (few tens of watts) and minimum time.

Development of wire spraying for direct micro-patterning via an atmospheric-pressure UHF inductively coupled microplasma jet

We developed wire spraying for direct micro-patterning via an atmospheric-pressure inductively coupled microplasma (AP-ICMP) jet of 20–50 μm in diameter. A 50–100-μm diameter metal wire inserted in the nozzle was melted or evaporated efficiently at a few tens of watts by inductive heating as well as heat conduction from the microplasma and the resulting atomized droplets were jetted out with plasma-gas flowing. Most of the sprayed grains were oxidized during the processing and a deposit composed of metal oxide grains built up locally on the polymeric substrate. Because of the low heat flux due to small plasma size and low energy supply, this spraying is useful for deposition on low melting-point polymeric substrates. Additionally, the feasibility of line drawing with micron-width was demonstrated by linear translation of the substrate.

Fabrication of spherical carbon via UHF inductively coupled microplasma CVD

We developed a CVD system employing inductively coupled micronplasma generated by applying UHF (UHF microplasma). This system can be operated easily in air at atmospheric pressure with a few tens of watts of UHF power and enables us to deposit material on a wide variety of substrates. Deposition of carbon from CH4/Ar gas on the substrate without additional heating at atmospheric pressure in ambient air resulted in the formation of spherical graphites on a micron-sized region, at a growth rate of about 2 µm min−1. In addition, carbon nano-onions of sub-30-nm diameters were formed in large quantity. Our results seem to suggest that this microplasma CVD system may be utilized in the near future for low-temperature preparation of crystallized nanostructures, leading to simplified fabrication of the nano-scale device.

CLIO: Collaboration for an infrared laser at Orsay

The CLIO collaboration has started in 1986 in order to build an infrared laser at LURE at Orsay. It includes the design and construction of a new FEL dedicated rf linear accelerator. The goal is to make a broadly tunable laser (at least in the range 2–20 μm), of high peak power (MW range), and “medium” average power (a few tens of watts). It will be utilized as a “user facility” as well as for FEL fundamental studies. The linac uses a gridded disperser cathode gun, a 500 MHz prebuncher, a fundamental buncher and one accelerating section powered by a 3 GHz klystron (with 12 μs long pulses). The final energy will be adjustable between 30 and 75 MeV. The desired characteristics are: peak current >50 A, total energy spread ≈1%, normalized emittance <150 πmm mrad. The numerical simulations made with PARMELA indicate that these performances will be reached with an emittance better by a factor of 2–4. The accelerator is followed by an achromatic and nearly isochronous 60° bend. It will allow to select the particles within a given energy spread, before the undulator, and to analyse, with respect to time, their energy distribution after the undulator. The optical cavity is 4.8 m long (32 ns roundtrip time), compatible with the laser risetime (typically 100 passes) and the klystron pulse length of 12 μs. The undulator is made of two independently adjustable identical parts, 0.96 m long (24 × 4 cm) each; the second one can be tapered. This will allow to optimize both the optical gain and energy extraction at different wavelengths. The laser is scheduled to operate by the end of 1990.

High average power harmonic generation

High average power frequency conversion using solid-state nonlinear materials is discussed. Recent laboratory experience and new developments in design concepts show that current technology, a few tens of watts, may be extended by several orders of magnitude. For example, using KD*P, efficient doubling (> 70 percent) of Nd:YAG at average powers approaching 100 KW is possible; for doubling to the blue or UV regions the average power may approach 1 MW. Configurations using segmented apertures permit essentially unlimited scaling of average power. High average power is achieved by configuring the nonlinear material as a set of thin plates with a large ratio of surface area to volume, and cooling the exposed surfaces with a flowing gas. The design and material fabrication of such a harmonic generator is well within current technology.

CaF&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;:Dy&amp;lt;sup&amp;gt;2+&amp;lt;/sup&amp;gt;lasers

The fabrication and operation of CaF 2 :Dy2+lasers are considered in detail. Laser action occurs at 4238.5 cm-1(extrapolated to 0°K) between the states T 1 (5I 7 ) \rightarrow T_{2} (5I 8 ).Chemical or electrolytic reduction techniques produce the most stable laser rods. The fluorescent lifetime of the (5I 7 ) states depends primarily upon the total Dy concentration in the crystal and varies from over 50 ms at low concentrations to 10 ms at 0.2 percent dysprosium. This lifetime is essentially temperature independent. The operation of the laser in a magnetic field is analyzed. By aligning the magnetic field and the laser axis parallel to the crystalline [100] axis, modulation of the laser output can be obtained at rates up to 1 MHz with a few tens of gauss modulating field. The saturation in laser output power at high levels is due to the finite lifetime of the (5I 7 ) multiplet, which is estimated to be several ms. The fluorescent linewidth of the laser transition varies from 4 cm-1at 200°K to 0.024 cm-1at 4.2°K. The absolute energy of the transition shifts 2.0 cm-1over the same temperature range with a slope of -0.009 cm-1/°K at 77°K. A technique of cooling the crystal with flowing, nonboiling liquid N 2 permits high-level laser operation near 77°K. Power outputs up to 1.21 watts have been obtained from CaF 2 :Dy2+when the crystal is pumped optically with two 1-kW tungsten lamps in a double ellipse. Under these conditions, the crystal temperature rises 15 to 20° above the coolant due to the high thermal resistivity of the crystal-liquid nitrogen interface. Typical pulse thresholds at 77°K are 20 joules into an FT524 lamp. The threshold drops rapidly at lower temperatures, but is strongly dependent on the frequency separation between the narrow fluorescent line and the cavity modes. Measurements at 4.2°K are particularly difficult because of this effect. Continuous operation at 27°K has been obtained at electrical inputs to the tungsten lamp as low as 20 watts. Laser output consists of a continuous output modulated at 20 to 100 kHz, with spherical reflectors or a pulsed, on-off output with flat reflectors. With spherical reflectors, magnetic feedback can be applied to reduce the amplitude of the modulation to less than 10 percent. The same type of magnetic modulation can be used to obtain a series of output pulses phase locked to the modulating frequency. The modulating frequency can be varied from a few kHz up to almost a MHz. The most effective modulation was obtained with an inhomogeneous modulating magnetic field and with the laser axis parallel to the crystalline [100] direction. At low modulation frequencies and with high fields, quasi- Q - switched operation was obtained. Q -switching was also observed with an external rotating mirror, which gave a series of pulses of 20 ns rise time. These did not have the characteristic high power of Q -switched pulses but peak powers of only a few tens of watts. This is assumed to be caused by the absorption of the metastable (5I 7 )level. The single-pass gain of a laser amplifier was measured; it corresponded to \alpha=0.039 cm-1.