Coaxial Switch Research Articles

Detection of ion cyclotron emission by using an ion cyclotron range of frequency antennas-based diagnostic system in experimental advanced superconducting tokamak

In the experimental advanced superconducting tokamak (EAST), a novel ion cyclotron range of frequency (ICRF) antenna-based diagnostic system is designed to measure ion cyclotron emission (ICE) driven by high-energy ions. The diagnostic system includes ICRF antenna straps, a three-tune impedance matching system, a coaxial switching system, a direct current block, and a data acquisition and storage system. Using the coaxial switching system, the ICRF antenna can be switched from the heating mode to the coupling mode between two discharges. In the 2023 EAST experiment campaign, core ICE was observed using the ICRF antenna-based diagnostic system during neutron beam injection heating, and the obtained results agreed well with the signal detected by the previous high-frequency B-dot probe-based diagnostic system.

Numerical investigation of multipactor discharge in coaxial switches

Findings in the research on conditions for occurrence of a multipactor discharge in coaxial switches have been presented. A model of a powerful coaxial microwave SPDT switch operating in the frequency range below 1.7 GHz has been obtained. Calculated values of the electrical parameters have been given and the possibility of manufacturing a coaxial switch for spacecraft with an operating power margin has been shown. The manufactured prototype of the microwave switch can withstand at least 400 W of RF power at a frequency of 1 GHz, which has been confirmed by the experiment.

Design and control of coaxial switching system for ion cyclotron wave resonance heating system of EAST

Ion cyclotron wave resonance heating system (ICRH) which is one of the most important auxiliary system in EAST provides conditions for heating the plasma. In order to make the whole transmission network of ICRH form the required state, the coaxial switching system was developed, which mainly consists of 11 same coaxial switches. Each coaxial switch has a controller with an RS485 communication interface and is able to switch between two states. All controllers are integrated to an RS485 hub which connects to the computer. A master computer software is developed to control the coaxial switching system so as to achieve the state needs of ICRH. Moreover, several rounds of experiments show that the coaxial switching system operates reliably. The coaxial switching system has already been applied to normal use currently.

Dynamical Correlations for Statistical Copolymers from High-Throughput Broad-Band Dielectric Spectroscopy.

Broad-band dielectric spectroscopy (BDS) provides a powerful method of characterizing relaxation dynamics in diverse materials. Here we describe and employ a novel instrument for high-throughput broad-band dielectric spectroscopy (HTBDS) that accelerates this capability, enabling simultaneous measurements of 48 samples. This capability is based around a coaxial switching system for rapid scanning between multiple samples on the same sample stage, coordinated with shared environmental control. We validate the instrument by measuring dielectric response in three polymers, distributed across 48 sample sites, and comparing results to measurements via a standard BDS instrument. Results are found to be reproducible and are in agreement with relaxation times from traditional BDS. We then employ HTBDS to establish mixing rules for glass transition temperatures, kinetic fragility indices, and segmental stretching exponents in a series of acrylate copolymers, a matter of considerable technological interest in a variety of technological applications. Results are consistent with the empirical Fox rule for the glass transition temperature Tg averaging in polymer blends, while they reveal a linear mixing rule for kinetic fragility indices. Finally, we test several proposed correlations between these distinct dynamical properties. These results demonstrate that HTBDS enables measurements of polymer relaxation at a throughput approximately 10 times higher than that of standard BDS approaches, opening the door to high-throughput materials design of dynamic response across a broad range of frequencies.

Techniques for shaping of the output pulse in high current generators

This paper presents the design and test of a 0.5 MA generator with a tunable pulse shape. The main parts are: the storage capacitor (3.95 μF ∼ 12.6 kJ at 80 kV), multi-channel coaxial switch, strip transmission line, load, pulse forming block (two versions are considered here, namely with peaking capacitor and wire opening switch). A set of inductances in parallel with the peaking switch as well as using various gases into this switch allow us to modify the current wave shape. Jitter from shot to shot did not exceed 10 ns in the experiments. This paper describes the design of main module elements and the results of experiments for two schemes at operation on load equivalent. In combination of the two pulse forming blocks, the generator proves the possibility of pulse shape tuning in a very wide range, namely delivering between 400 and 600 kA with a 200–800 ns rise time. The generator weight was ∼ 200 kg and the dimensions are 1x0.6x0.8 1 m3 with a pumping system. The generator design allowed for an easy increase in the number of modules in the arbitrary series–parallel combination in order to get the required current amplitude and pulse shape. Operation and handling are very simple, because no oil, water, nor SF6 are required for the generator.

Study on the Influence of Creep on RF Coaxial Switch in Accelerated Thermal Cycle Test

Radio frequency (RF) coaxial switches have the advantages of high transmission frequency and power capacity and are widely used in aerospace, communications, military, science, and medical fields. In accelerated thermal cycle (ATC) test, a permanent deformation or displacement occurs in the contact system of RF coaxial switch caused by creep and the RF performance downgrades with the thermal cycle times. In this paper, a 3-D finite-element model of an RF coaxial switch was first proposed. The power loss in the contact system when the switch transmits high frequency and power signals was divided into the conductor loss and the dielectric loss, which were calculated separately. It was noted that conductor loss was the main part of power loss. Then, the power loss in the contact system was considered as the heat source, and the steady-state temperature field of the whole switch was calculated with Ansoft HFSS and Workbench. The temperature rise in an RF coaxial switch was calculated and verified by experimental testing. In order to predict the reliability and working life of RF coaxial switch in ATC test, a creep constitutive equation based on the Coffin–Mason method that has three undetermined coefficients was built. According to ISO204:2009 (Metallic materials-Uniaxial creep testing in tension), the samples of beryllium bronze for creep testing were produced, and two groups of creep testing in the condition of different temperatures and stresses were carried out to obtain the undetermined coefficients. Finally, the stress–strain deformation of contact system with the thermal cycle times was calculated based on the creep constitutive equation. The model of contact system was rebuilt, and the influence of creep on RF coaxial switch in ATC test was investgated. The analysis methods and conclusions presented in this paper have important theoretical significance and practical value for improving the performance and reliability of RF coaxial switch products.

A Reconfigurable Four Terminal-Pair Digitally Assisted and Fully Digital Impedance Ratio Bridge

A reconfigurable digital bridge for calibrating four terminal-pair (4-TP) defined impedance standards in the whole complex impedance plane by means of fully digital (FD) operation of the bridge and for R-R,C-C calibration and ac quantized Hall resistance experiments by involving reference inductive voltage divider in digitally assisted (DA) configuration has been built at CMI in recent years. For the purposes of the bridge, high-accuracy digital voltage sources operating in the audio frequency range with full isolation between modules and with battery operation mode have been developed. Together with coaxial switches with negligible crosstalk between channels, the voltage sources form the basis for full automation of the calibration process. The bridge has been tested in both FD and DA configurations. Depending on the configuration, different relative accuracies of the measurements can be achieved in the range from a few parts in 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> to a few parts in 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> .

A microwave coaxial switch

Microwave coaxial switch on p-i-n-diodes is described. The device is a section of a coaxial line with a broken external conductor. The control p-i-n-diodes are embedded into the break (annular gap) of the conductor. A toroidal resonator, the gap of which is in line with the break of the external conductor of the coaxial line, is axially aligned to the line. The device is made in versions with working frequencies of 2450 and 2856 MHz; maximal pulse microwave power of 3 (2A520A p-i-n-diodes), 1 (2A507A), and 0.2 kW (2A509A); and leading edge of microwave pulses of no more than 200, 50, and 30 ns, respectively.

An Automated-Switching Precision Decade Capacitor

A new automated-switching precision decade capacitor for applications in industries was designed and tested. By using coaxial microwave switches, the automated-switching precision decade capacitor can be automatically set by electrical TTL signals controlled by a computer. To prevent capacitance from drifting caused by variations of ambient temperature, the internal temperature of the automated-switching precision decade capacitor was effectively kept constant using a temperature-controlled oven with sufficiently thermal isolation. Furthermore, to fulfil the compact-size requirement for using at a high frequency, SMD capacitors with NP0 dielectric were used. The temperature stabilities and linearity of the automated-switching precision decade capacitor are presented in this paper.

Plasma density evolution in plasma opening switch obtained by a time-resolved sensitive He-Ne interferometer

To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch (POS), we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer. The conduction current and conduction time in experiments are about 120 kA and 1 μs, respectively. As a result, more than 85% of conduction current has been transferred to an inductive load with rise time of 130 ns. The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters. During the conduction phase, the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns. The current conduction is observed to cause a radial redistribution of the switch plasma. A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor, which is consistent with the location where magnetic pressure is the largest, allowing current to be transferred from the POS to the load.

Experimental Study of a Submillimeter Spark-Gap

This paper describes an experimental study on a submillimeter spark-gap and the effect of the gas type, pressure and interelectrode distance on the gas discharge. A coaxial transmission-line test switch and stainless steel electrodes have been used for the laboratory tests. The results presented in this paper are obtained using air, SF6, and argon, at gas pressures between 174 and 774 kPa and interelectrode distances from 330 to 450 μm. Results show that there is a linear change in breakdown voltage as the pd-relation increases. Important differences are observed when the time of the resistive phase is calculated and compared with the one obtained with some empirical models. It is also found that the arc-resistance depends on the gas type, and it is almost proportional to pd. The Kushner arc-resistance model fits well with the laboratory test results. From these results, a new constant of proportionality depending on electric field, pressure, and interelectrode distance is proposed. Additionally, for the studied pd-range, the gas with the best-fitting results was SF6. Finally, a good fit is observed between the laboratory test results and the obtained models programed in the computer program electromagnetic transient program.

纳秒脉冲电压下同轴场畸变开关多通道放电特性

纳秒脉冲电压下同轴场畸变开关多通道放电特性

A Broadband Spectroscopic Sensor Probe

Abstract The electrical properties of many materials are closely related to their composition and to their moisture content in particular. For sensor development, characterising the response of a particular volume of material over a broad frequency range is desirable, since separate measurements could generate errors due to spatial variability. A coaxial probe has been designed for measurement of the permittivity of smooth and flat, solid or liquid samples over the frequency range from 1 Hz to 6 GHz. Although the probe is capable of a very wide frequency range, separate instruments are generally required, and here we focus on measurements above 1MHz. We demonstrate measurements in the frequency domain using a vector network analyser, and in the time domain using a broadband oscilloscope. For switching, we employed a coaxial switch and demonstrate how that is included within the instrument calibration. Calibration of the probe used three

Magnetohydrodynamic Simulation of a Coaxial High-Density Plasma Opening Switch

The plasma dynamics and the magnetic-field penetration in a coaxial plasma opening switch (POS) are studied self-consistently based on the two-dimensional magnetohydrodynamic (MHD) equation conjunction with the generalized Ohm's law. The energy transfers between the plasma and the magnetic field are considered during the penetration of the magnetic field, in which both the Ohmic heating and the heat transfer are included in the energy-balance equation. The profiles of magnetic field, plasma density, and plasma temperature are simulated with the initial plasma density n0=1016 cm-3. For the high-density plasma, it is shown that the convection effect dominates the magnetic-field penetration; the plasma near the cathode is rapidly compressed by the magnetic pressure, and the temperature of the plasma in the shock region increases noticeably because of the compression effect. Furthermore, the increase of temperature in the shock region enhances the magnetic-field penetration near the cathode. The energy analysis shows that more than half of the input energy is stored as magnetic-field energy, and a significant amount of the input energy goes into the plasma thermal energy. The scaling relation between the maximal conduction current and the initial plasma density is also studied, and the simulation results agree with the theoretical law and experimental data well

In vitro measurement using a MEMS probe array with five-strip lines for permittivity measurement

This paper describes a single-aperture MEMS probe and a MEMS probe array for the measurement of biological properties. We designed and fabricated the single-aperture MEMS probe using surface micromachining and verified it by measuring the permittivity of a standard liquid before introducing the MEMS probe array. The actual aperture size of the single-aperture MEMS probe is only 390 µm × 80 µm, which is very small in comparison with the conventional laser-machined coaxial probe. In order to show the feasibility of the proposed single-aperture MEMS probe for permittivity measurements, we performed in vitro measurements of 0.9% saline. Once the single-aperture probe was verified, we proposed the concept of a probe array for biological measurements and experimentally showed the suitability of the MEMS probe array for biological applications through experiments using pork. The MEMS probe array consists of five microstrip feed lines, each of which is followed by open-ended strip lines, and the permittivity measurement of each port is separately performed through the use of a conventional multiport coaxial switch (Agilent, HP 87106 C), followed by a network analyzer (HP 8510 C). Through broadband measurements of 0.9% saline and pork using the MEMS probe array, we were able to discriminate the muscle and fat of pork through just one contact by placing the MEMS probe array on the boundary of muscle and fat. This newly proposed MEMS probe array has great potential in terms of disposability, low cost, integration with planar circuits and a short detection time for biological measurements.

Multiport MEMS-based waveguide and coaxial switches

In this paper, a new concept of three-dimensional (3-D) multiport RF microelectromechanical systems (MEMS) switches is introduced. The proposed structures are based on integrated MEMS actuators inside 3-D waveguide and coaxial structures. These switches are well suited for high-power redundancy switch matrices for satellite communication, as well as millimeter-wave applications. To demonstrate the concept, a C-type waveguide switch is fabricated and tested. The use of a unique bi-layer curled electrostatic actuators, results in a very good RF performance with an isolation of 36-40 dB and a return loss of -20dB over a 7% bandwidth at satellite Ku-band. This paper also presents for the first time a new type of MEMS-based coaxial switch, which can offer a much larger bandwidth with miniaturized dimensions. To prove the concept, prototype units of single-pole single-throw and C-type switches are designed, fabricated, and tested. The measured results demonstrate a bandwidth of 65% for the C-type MEMS-based coaxial switch.

Focus on Data Acquisition

Focus on Data Acquisition

Observation of plasma motion in a coaxial plasma opening switch with a chordal laser interferometer

Electron densities in a coaxial plasma opening switch were measured at many lines-of-sight. In the present experiment, electron density was measured by a He-Ne laser interferometer with chordal lines-of-sight. In order to observe the motion of the plasma opening switch (POS) plasma, the electron density contours during the conduction, opening, and postopening phases were drawn by combining the results of interferometer experiments. The radial and axial motion of POS plasma was investigated from the density contours. As conduction time progressed, the POS plasma moved toward downstream. At 800 ns, which corresponds to the time of opening in the current waveform, low-density region less than 10/sup 15/ cm/sup -2/ is seen at 10 mm from the cathode. After the opening was completed, the low-density gap disappeared and the shape of the corn-shape-like plasma was distorted. The interferometer experiment was followed by the additional spectroscopic experiment. The results of spectroscopic experiment were in good agreement with those of interferometer experiment.

A remotely controlled coaxial switch for impedance standard calibration

A switch which permits the connection, in sequence, of a couple of four-terminal-pair impedance standards to an automatic RLC bridge, is presented. The purpose of the switch is to automate the process of impedance calibration by 1:1 substitution. The switch is capable of engaging four coaxial lines at a time (switching both the internal conductor and the screen of each line); the electrical contacts are British Post Office MUSA connector. The switch, in the closed position, adds 2 m/spl Omega/ of resistance to each coaxial line in the electrical path. The switch is moved by pneumatic actuators to avoid any electrical interference, and is remotely controlled via RS-232 interface. Measurement examples are shown.

Experimental investigation of a 25-MW microwave (3-cm range) compressor prototype

An experimental study of a resonance microwave (3-cm-range) compressor with gas insulation and energy output through a superdimensional coaxial interference switch is reported. The rated parameters of the compressor are output signal power ∼25 MW, signal duration 2 ns, gain 26 dB, and efficiency ∼57%. A gain of 20 dB was achieved at a peak output signal power of 12 MW, signal duration of 2 ns, efficiency of ∼24%, and traveling wave power of 24 MW.