kW Of Input Power Research Articles

High power, broadband, coaxial to microstrip bi‐directional coupler in the VHF/UHF band

AbstractBroadband couplers consist usually of multiple coupled lines that are each a quarter wave‐length long. Herein, in contrast to conventional methods, a short length of a microstrip line is coupled to a coaxial line. The length of the coupled microstrip line is small compared to the wavelength at the lowest operating frequency. The coupling is weak and the microstrip line is λ/8 at the highest operating frequency. The proposed structure resembles a pair of coupled lines with a linear coupling response. The coupling exhibits a slope of 6 dB/octave over multi‐octave bandwidth. The microstrip line is connected to a lumped element compensating network at the coupled port. The compensating network is a low‐pass circuit with a slope of −6 dB/octave. The power handling of the coupler is high due to the coaxial line and the weakly coupled microstrip line. Electromagnetic simulations and analytical formulations are presented. The broadband coupler handles nearly 1 kW of input power. Due to the weak coupling of the microstrip‐coaxial coupler, the lumped element circuit needs to handle <1.5 W. A high‐power coupler has been fabricated for the frequency range of 30 to 500 MHz. It exhibits a coupling response of 56 ± 0.4 dB.

Design and simulations of the HEBT spiral buncher cavities for the high current injector at IUAC

The high energy beam transport (HEBT) section of the high current injector (HCI) accelerator requires two spiral buncher (SB) cavities to match the input Twiss parameters at the entrance of the superconducting super buncher (SSB) cavity by providing the longitudinal phase matching between drift tube linac (DTL) and SSB. The spiral type open-ended quarter-wave (λ/4) resonators were chosen for their high shunt impedance, mechanical, and vibrational stability. The 48.5 MHz frequency of cavities was chosen for its broad acceptance of time width. TRACE 3D codes were simulated to determine the bunching voltage for the spiral buncher cavities. The locations of HEBT spiral bunchers have been fixed in such a way that the ion beam can be transported from DTL to SSB with negligible growth in longitudinal beam emittance within the framework of first-order linear beam optics. The cavity parameters were optimized to get the significantly high shunt impedance and quality factor to achieve the desired electric field level at the minimum input power. The inner and outer radii of the drift tubes were honed to get the uniform electric field profile along the beam direction while βλ/2 was kept constant during the refinement. The HEBT SB cavities require ~2 kW of input power to produce ~160 kV across two RF gaps. The simulated quality factor and shunt impedance for two identical HEBT SB cavities are ~8300 and ~13.5 MΩ, respectively. The cylindrical type chamber will be fabricated of copper-plated mild-steel (MS) while other components including end plates, spiral, stem, and flanges were fabricated of pure OFHC copper due to excellent electrical as well as thermal conductivity. The cavity frequency can be easily coarse tuned by varying the length of the spiral. The distinguishing feature of the design is to tailor the cavity frequency by ±250 kHz by varying the diameter of the drift tubes and stem, even after fabrication. A cylindrical type frequency tuner of diameter 90 mm and thickness 10 mm has been designed which is capable of providing the additional frequency correction of ± 250 kHz in the travel distance of ~200 mm. The details of longitudinal beam optics, ion-optical and electrical design, simulations, and mechanical design are discussed in this article.

On the Opportunity of Liquid Metal Rotated Anode for High Brightness X-Ray Source

The new generation compact X-ray source for semiconductor metrology requires a brilliance that is higher than existing technology can offer. In this article, we propose a new X-ray source anode where an electron beam is focused on a rotating liquid metal layer. We assume that high brilliance emission can be achieved with power densities in the range of 1–10 MW/mm2 in the focal spot. The liquid tin layer is formed on top of the rotating anode disk electrode which is partially immersed in liquid tin. This scheme has recently been implemented in the plasma-discharge-based 13.5-nm extreme UV source of the EBL-2 beamline system at TNO. The existing technology of liquid tin circulation can provide cooling of up to 10 kW of input power with peak power densities up to 5 MW/mm2. An opportunity to use a liquid metal layer with the thickness of several tens of micrometers on the fast-rotating metal disk is discussed.

Synthesis of boron nitride nanotubes using triple DC thermal plasma reactor with hydrogen injection

Highly crystalline boron nitride nanotubes (BNNTs) having multi-walls (≤5 walls) and a small diameter (~7 nm) were synthesized using a triple DC thermal plasma reactor with hydrogen injection. Triple torch configuration not only generates larger high temperature regions than single torch but also allow precursors to directly penetrate the core of the plasma flame, the hottest area in the reactor. A triple torch increases the productivity of BNNT synthesis by preventing the flow of precursors into the rim of plasma flame, a problem that occurs with single torch due to the high velocity and viscosity of the central flame. The role of hydrogen in the growth of BNNTs was analyzed by thermodynamic equilibrium reaction calculations and numerical analysis of thermal flow in the system. The reaction calculations revealed that hydrogen facilitates the formation of NH, NH2, and N2H2 molecules by inhibiting N from recombining into N2 in the high temperature region. Hydrogen influences the formation of scattered high temperature and enthalpy regions due to its thermal properties and expands the vortex region, leading to longer residence times for B-N-H intermediates in the reactive region. As a result, 12.6 g of BNNTs are produced with 21.4 kW of input power. A comparison with other methods shows that this yield is superior and provides an economic perspective for the proposed pilot synthesis of BNNTs.

Negative ion characterization in a helicon plasma source for fusion neutral beams by cavity ring-down spectroscopy and Langmuir probe laser photodetachment

Negative ions are characterized in the helicon plasma source resonant antenna ion device (RAID) at the Swiss plasma center by means of cavity ring-down spectroscopy (CRDS) and Langmuir probe (LP)-assisted laser photodetachment. A high density and axially homogeneous plasma column is produced via a RF antenna able to sustain the propagation of helicon waves in a steady state regime. An electron density in plasma at 0.3 Pa and 3 kW of input power is measured in the center of the plasma column by LP and microwave interferometry. The electron temperature profile is peaked on axis reaching and decreasing to 1.5 eV at . Thus, a hot core region forms where molecules are rovibrationally excited (), and a cold edge, where low energy electrons can attach to and produce ions by dissociative attachment. In this work we use LP-assisted laser photodetachment and CRDS diagnostics to measure and radial density profiles and how they depend on source parameters. We show that negative ions are distributed on a shell of 0.06 m radius with a peak value of ∼ in plasma. These results suggest that, although substantial technical development is needed, helicon plasmas could be considered as a possible candidate as sources of negative ions for future NBIs.

A non-perturbing technique to characterize the indigenously developed spiral buncher cavity at high-power level

Abstract The High Current Injector (HCI) at Inter-University Accelerator Centre (IUAC) incorporates a spiral buncher cavity to provide the time bunching of charged particles at the entrance of Drift Tube Linac (DTL). The spiral buncher cavity is a two-gap RF structure with its remarkable properties such as high shunt impedance, compactness, and high-frequency stability. The cavity was designed, developed, assembled, and successfully tested at IUAC. The cavity has been designed for ∼ 27 kV/gap at ∼ 1 kW of input power. At the low power level, the bead-pull technique was used to characterize the cavity, and the X-ray energy spectroscopy method was used to characterize the cavity at a high-power level. The X-ray measurement technique was used to determine the gap voltage across the drift tubes without perturbing the field. A thallium doped sodium iodide-based scintillator detector was used to measure the emitted X-ray from a cavity. The cavity was powered at a variable power level, and the X-ray energy spectrum was recorded. The measured and simulated results match closely within the error of ∼ 5%. The details of cavity characterization, high-power testing, and X-ray energy measurement method will be discussed in the article.

Compact MR-compatible DC-DC converter module

The SAFIR collaboration is developing a high rate positron emission tomography insert for a preclinical 7 T magnetic resonance imaging (MRI) device. To meet the desired performance figures, a large number of readout channels (≈15000) and integration of data digitisation into the insert are required. Consequently, the insert will consume about 1.3 kW of input power at low voltages (⩽ 3.3 V). This corresponds to large supply currents of several 100 A, requiring heavy and bulky supply cables. To overcome these problems we developed a compact and MR-compatible DC-DC stepdown converter module. Our converter is based on an air core inductor and is optimised for low electromagnetic emissions. It has an input voltage range from 6 V to 24 V and provides an adjustable output voltage from 1 V almost up to the input voltage. The maximum continuous output current is 6 A. We measured conversion efficiencies between 70% and 87% depending on output load and input voltage. For the operation conditions foreseen (16 V input voltage, 2.4 V output voltage and 3 A output current), we achieved an efficiency of 83.8%. Our tests inside the MRI demonstrated the compatibility between the MRI system and the step-down converters developed. No mutual interference was observed. The signal-to-noise ratio of the MRI remains unaltered, independent of the activity of the step-down converter under any operation condition and no effect on the operation of the DC-DC converter was observed. This successful test of an MR-compatible DC-DC converter creates new opportunities for the power supply of complex hardware inside an MRI. 49 of the DC-DC converters will be used in our SAFIR PET insert, but they can also be used in other applications with high power demand in environments with strong magnetic fields.

RF conditioning for the improvement of lower hybrid fast wave comb-line antenna performance on VEST

RF conditioning is conducted to improve coupling and current drive performance of the comb-line antenna which is to excite fast wave in lower hybrid resonance frequency range in Versatile Experiment Spherical Torus (VEST). It has been observed that considerable outgassing, power dissipation and high reflection take place while diminishing transmitted power with poor reproducibility without the RF conditioning process which cleanses antenna surface by RF surface heating. Outgassing source during the RF conditioning is identified mainly as water vapor. A new dimensionless figure-of-merit to evaluate degree of the RF conditioning is defined with dissipated power and outgassing rate by analyzing experimentally observed RF conditioning data. Optimum performance of the antenna with low figure-of-merit (5 × 10−9) is achieved after conditioning for 3 days a week (∼40 shots) at less than 10 kW of input power. Coefficients of transmission, reflection, and dissipation reach to about 80%, 2%, and 18%, respectively indicating almost doubled antenna performance. Introduced new figure-of-merit provides a quantitative basis for antenna conditioning in order to improve antenna performance.

Cavity ring-down spectroscopy to measure negative ion density in a helicon plasma source for fusion neutral beams.

Cavity Ring Down Spectroscopy (CRDS) is used to measure the D- absolute density produced in the helicon plasma reactor RAID (Resonant Antenna Ion Device) at the Swiss Plasma Center. The birdcage geometry of the helicon antenna produces a homogeneous, high-density plasma column (n e ≅ 1.5 × 1018 m-3 in H2 and D2 at 0.3 Pa and 3 kW of input power) 1.4 m long. We present the CRDS experimental setup, its positioning on the RAID reactor, and how the mechanical and thermal effects of the plasma affect the measurement. First results in deuterium plasma confirm the production of negative ions (D-) with a significant density: an average value of 3.0 × 1016 m-3 of D- is obtained at 0.3 Pa and 5 kW of power input in Cs-free plasma. This result is in good agreement with calculations performed with the collisional radiative code YACORA.

Power accounting of plasma discharges in the linear device Proto-MPEX**This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of

Plasma material interaction (PMI) studies are crucial to the successful development of future fusion reactors. Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a prototype design for the MPEX, a steady-state linear device being developed to study PMI. The primary purpose of Proto-MPEX is developing the plasma heating source concepts for MPEX. A power accounting study of Proto-MPEX works to identify machine operating parameters that could improve its performance, thereby increasing its PMI research capabilities, potentially impacting the MPEX design concept. To build a comprehensive power balance, an analysis of the helicon region has been performed implementing a diagnostic suite and software modeling to identify mechanisms and locations of heat loss from the main plasma. Of the 106.3 kW of input power, up to 90.5% of the power has been accounted for in the helicon region. When the analysis was extended to encompass the device to its end plates, 49.2% of the input power was accounted for and verified diagnostically. Areas requiring further diagnostic analysis are identified. The required improvements will be implemented in future work. The data acquisition and analysis processes will be streamlined to form a working model for future power balance studies of Proto-MPEX.

Cascading pulse tubes on a large diaphragm pressure wave generator to increase liquefaction potential

Fabrum Solutions, in collaboration with Absolut System and Callaghan Innovation, produce a range of large pulse tube cryocoolers based on metal diaphragm pressure wave generator technology (DPWG). The largest cryocooler consists of three in-line pulse tubes working in parallel on a 1000 cm3 swept volume DPWG. It has demonstrated 1280 W of refrigeration at 77 K, from 24 kW of input power and was subsequently incorporated into a liquefaction plant to produce liquid nitrogen for an industrial customer. The pulse tubes on the large cryocooler each produced 426 W of refrigeration at 77 K. However, pulse tubes can produce more refrigeration with higher efficiency at higher temperatures. This paper presents the results from experiments to increase overall liquefaction throughput by operating one or more pulse tubes at a higher temperature to pre-cool the incoming gas. The experiments showed that the effective cooling increased to 1500 W resulting in an increase in liquefaction rate from 13 to 16 l/hour.

Analysis of effect of impeller geometry including blade outlet angle on the performance of multi-pressure pumps: Simulation and experiment

In this paper, the effect of outlet angle geometry of the blades of the impeller of a multi-pressure pump on the pump’s head and efficiency using two approaches, namely numerical approach (Computational Fluid Dynamics) and experimentation are investigated. Herein, a closed single-suction, five-blade impeller with three different outlet angles (27°, 30°, and 33°) is analyzed. The impeller model was first built in SOLIDWORKS software before analyzing the fluid flow with the help of ANSYS Fluent software. All surfaces were meshed through irregular gridding. Considering high flow velocity along with low thickness of boundary layer near the blade tips, smaller mesh sizes were used across these areas. Blade surfaces were meshed using square elements. Furthermore, in order to model the volumes, irregular gridding and TGrid algorithm were undertaken. Generated with this algorithm are quadtrial elements of known size. In volumetric meshing stage, aspect ratio was set to a maximum of 0.6. In the experimentation phase of this research, a multi-stage pump was tested at 2000 rpm and 30 kW of input power with three impellers of different angles. At specific values of outlet angle and impeller outlet width, some reductions in hydraulic and mechanical losses within the impeller along with some rises in the pump head and efficiency were observed. Simulation results were found to be in good agreement with the experimental data; so as one can save time and money by using numerical simulation approaches in ANSYS Fluent rather than undertaking experimentations. Numerical and experimental analyses revealed that the maximum pump head and efficiency have been witnessed at the outlet angle of 30°. This is because of the reduced losses by water recirculation within the volute and outlet impellers.DOI: http://dx.doi.org/10.5755/j01.mech.23.1.17676

Complementary split-ring resonator-based accelerating structure

We describe a novel particle accelerating structure consisting of Complementary Split-Ring Resonators (C-SRRs) etched into the lower and upper walls of a copper rectangular waveguide. Outer cylindrical cavities enclosing the C-SRR sections allow a vacuum to be maintained. The accelerating gradient of a 1 GHz cavity is simulated to be 8.76 MV/m, when referenced to the actual accelerating gap, for only 10.7 kW of input power. Particle simulation results confirm the efficacy of the proposed structure. A simple analytical model of the structure is given as a design aid to compute the relationship between the key geometrical parameters and the resonance frequency.

High power light gas helicon plasma source for VASIMR

In the Advanced Space Propulsion Laboratory (ASPL) helicon experiment (VX-10) we have measured a plasma flux to input gas rate ratio near 100% for both helium and deuterium at power levels up to 10 kW. Recent results at Oak Ridge National Laboratory (ORNL) show enhanced efficiency operation with a high power density, over 5 kW in a 5 cm diameter tube. Our helicon is presently 9 cm in diameter and operates up to 10 kW of input power. The data here uses a Boswell double-saddle antenna design with a magnetic cusp just upstream of the antenna. Similar to ORNL, for deuterium at near 10 kW, we find an enhanced performance of operation at magnetic fields above the lower hybrid matching condition.

Sheet-shaped plasma production using microwave-plasma interaction with ECR region

New phenomena in producing sheet-shaped plasma under electron cyclotron resonance (ECR) condition have been found and investigated by experiment. Sheet-shaped Ar plasma with density of /spl sim/10/sup 18/ m/sup -3/ was successfully obtained at /spl sim/10/sup -3/ torr by using 2.45-GHz microwave with ECR condition. The plasma was generated uniformly and stably in the cross section of 15.5 cm width/spl times/2.0 cm thickness with the use of waveguide of the rectangular cross section under the quartz window in vacuum. The parameter region of stable sheet-shaped plasma production was made clear by experiments clarifying criteria in parameter map. It was found that the magnetic field strength corresponding to the position and the shape of ECR region was the most effective parameter affecting microwave propagation to control the shape of plasma. However, the uniformity of the sheet-shaped plasma width was poor over the distance of microwave wavelength /spl lambda/ under 1 kW of input power. Therefore, it was concluded that the microwave was absorbed quickly near ECR region and hardly propagates farther than /spl sim//spl lambda/ to the direction of perpendicular to the magnetic field. The double sheet-shaped plasma was produced at some region and two peaks were relatively shifted to the direction of E/spl times/B. Also, the condition of sheet-shaped plasma production was different for helium gas. By the electron density measurement and semi-one-dimensional analysis, the differences of ionization cross section and diffusion coefficient perpendicular to the magnetic fields were important factors for electron density and the shape of sheet plasma. The qualitative interpretation of sheet-shaped plasma production is discussed.

The 1998 World Solar Rallye: Akita, Japan

Abstract In early August 1998, 81 solar/electric vehicles participated in a three day endurance race in Japan. The objective was to complete as many laps of the 31 km circuit as possible. Some of the cars used state-of-the-art motors, batteries, chassis, solar cells and tyres to produce vehicles which could travel at speeds of 70–80 km/h on about 1 kW of input power. With only 20 kg of battery, some solar cars were travelling around 450 km a day. This paper tells the story of the race and the technological developments behind the successful vehicles.

Microwave-driven multipurpose ion source

A microwave-driven ion source being developed at TRIUMF is designed to produce stable, reliable, and gas-efficient negative and positive ion beams for cyclotrons and other accelerators. The source has been tested for H− and achieved 2.1 mA at 0.25 π mm mrad normalized emittance for 500 W of input power at a frequency of 2.45 GHz. The source was operated over one month without interruption for a H− beam stability test and demonstrated 2.5% stability over the period. For positive beam extraction H+, He+, N+, and Ar+ species have been studied. A 2 mA N+ beam was obtained at 0.3 π mm mrad normalized emittance for 1 kW of input power. A beam density as high as 7 mA/cm2 with 45% gas efficiency has been achieved for the Ar+ beam. In this paper the source parameters and characteristics are discussed.

Results from an X-band coaxial extended length cavity

Experiments and simulations demonstrate high-power microwave generation at 9 GHz in a coaxial geometry. The 9 cm diameter annular electron beam is propagated between inner and outer drift tube conductors, a configuration which increases the beam current and reduces the structure fields from existing high-power sources, Since the TEM mode of the coaxial guide reduces the quality factor of small-gap cavities, especially at high frequency, the interaction is provided by an extended length cavity loaded with dielectric. A single 16 cm cavity generates 200 MW of power from the 400 keV, 7 kA electron beam. Although the cavity can oscillate at a number of resonances, a single mode is selected with 10-30 kW of input power from a magnetron. A coupler samples 25 MW of the power from the interaction region, precisely measured using a single-shot calorimeter. Simulations indicate that the efficiency of the device is limited to 7% by saturation effects, and can be improved by reducing the length of the cavity. >

ELF, VLF and LF radiation from a very large loop antenna with a mountain core

The establishment of an LF/VLF/ELF transmitting facility at the Homer tunnel near Milford South in the South Island of New Zealand is described. The antenna consisted of a 3.3 km-long PVC-covered aluminium conductor passing through the tunnel and over the mountain above, forming a large vertical loop antenna. Measurements of the electric field radiated from the transmitter, recorded at both Lauder and Palmerston, 133 and 225 km from the transmitter site, respectively, are presented. The antenna radiation pattern derived from observations made onboard an Orion aircraft circling the antenna at a distance of 200 km is also presented. Theoretical models are derived which enable fits to the radiated field data to be made over a wide frequency range (0.5–40 kHz). With 1 kW of input power the antenna produced peak radiated fields at frequencies near 10 kHz equivalent to those of a vertical monopole source radiating 150 mW.

Frequency chirp in a 10 ATM RF-excited CO/sub 2/ waveguide laser

Various mechanisms causing frequency chirping in multiatmospheric-pressure CO/sub 2/ lasers are discussed. The frequency chirp has been measured in a pulsed 10 atm CO/sub 2/ waveguide laser. It has been found that the dominating cause of the frequency chirp in this laser is heating of the gas by the RF discharge. The chirp increases with increasing RF input power. The chirp levels off at about 100-150 MHz/ mu s for 25 kW of input power. This leveling off the chirp is believed to be due to the negative lensing effect of the gas density perturbation. The effect of the anomalous dispersion on the chirp is observed when the laser is operated at the flanks of the CO/sub 2/ gain branches. >