Azimuthal Transmission Research Articles

A gas-insulated mega-ampere-class linear transformer driver with pluggable bricks.

This paper presents the design and test of a gas-insulated linear transformer driver (LTD) cavity aimed at the Z-pinch experimental device CZ-34. The LTD cavity has a diameter of 2290 mm and a height of 346 mm. It consists of 23 main bricks and 1 trigger brick. Each main brick is comprised of two 100 nF capacitors connected electrically in series with a field-distortion gas switch. The trigger brick is comprised of two 50 nF capacitors connected in series with a compact multi-gap gas switch. All bricks are placed in the cavity filled with compressed SF6 and are pluggable like drawers. The trigger pulse generated by the trigger brick passes through an azimuthal transmission line to the trigger ring and makes the main bricks discharge synchronously. The LTD cavity can deliver ∼1 MA current pulse with a rise time of 115 ns to 0.08 Ω liquid resistance load when the charging voltage is ±100 kV, which is in good agreement with the circuit simulation results. Experimental results demonstrate the successful application of using gas insulation and pluggable bricks. The technical feasibility of the charging configuration, triggering method, and isolation resistors is verified. There is little difference in output performance as return-current rods replaced the outside metal cylinder, which provides a new path for the design of LTD cavities in series.

ICEBEAR: An All‐Digital Bistatic Coded Continuous‐Wave Radar for Studies of the E Region of the Ionosphere

AbstractThe Ionospheric Continuous‐wave E region Bistatic Experimental Auroral Radar (ICEBEAR) is a coherent scatter ionospheric radar. It operates at a frequency of 49.5 MHz, which is ideal for observing E region coherent echoes. The radar is located in Saskatchewan, Canada, and is operated by the University of Saskatchewan. The ICEBEAR system uses a continuous‐wave (CW) signal and requires isolation between the receiving and transmitting arrays. This was accomplished through a bistatic setup, where the receiver and transmitter are ≈240 km apart. Currently, the ICEBEAR system implements a pseudo random noise phase modulation on this CW signal to obtain 3‐km range resolution and 5‐s integration time images of E region ionospheric irregularities over a 600 km × 600 km field of view. The center of the field of view is located at ≈58°N, 106°W. The radar design allows for future improvements to temporal and/or spatial resolutions. Each site consists of a linear phased array with 10 equally spaced antennas. This, combined with modern digital radio hardware, provides azimuthal angle of arrival measurements at the receiving array and azimuthal transmission control at the transmitting array. This publication describes the radio hardware and signal processing used by the ICEBEAR radar and emphasizes the unique capabilities of the radar. First ICEBEAR observations from a Kp ≥ 4 event on 10 March 2018, are presented and shown to produce simultaneously the four types of previously characterized E region coherent scatter echoes.

Design of a 1-MV induction cavity and validation of the two-dimensional circuit model

We present the design and test results of an induction cavity, which is a full-scale prototype cell of a prospective six-stage induction voltage adder. This induction cell runs in positive polarity and the output transmission line operates in the vacuum insulation state. The design methods and configurations of the azimuthal transmission line, insulation stack, magnetic core, cathode plate, and output transmission line in the induction cell are given in detail. The induction cavity is driven by one pulsed power system consisting of a tesla transformer, intermediate storage capacitor, laser triggered gas switch, pulse forming line, self-breaking oil switch, and a water transmission line. A maximum voltage about 1.05 MV could be achieved across one $7.0\text{ }\text{ }\mathrm{\ensuremath{\Omega}}$ water resistor load. A full circuit model including the primary energy storage section and pulse forming section is proposed. The circuit model also includes the two-dimensional circuit model of the induction cavity [Phys. Rev. Accel. Beams 20, 020401 (2017)]. The voltage and current waveforms across the feed port, azimuthal transmission line, insulation stack, and resistor load obtained during the experiment are compared with the circuit simulation results. It demonstrates that they can agree with each other very well.

Modeling power flow in the induction cavity with a two dimensional circuit simulation

We have proposed a two dimensional (2D) circuit model of induction cavity. The oil elbow and azimuthal transmission line are modeled with one dimensional transmission line elements, while 2D transmission line elements are employed to represent the regions inward the azimuthal transmission line. The voltage waveforms obtained by 2D circuit simulation and transient electromagnetic simulation are compared, which shows satisfactory agreement. The influence of impedance mismatch on the power flow condition in the induction cavity is investigated with this 2D circuit model. The simulation results indicate that the peak value of load voltage approaches the maximum if the azimuthal transmission line roughly matches the pulse forming section. The amplitude of output transmission line voltage is strongly influenced by its impedance, but the peak value of load voltage is insensitive to the actual output transmission line impedance. When the load impedance raises, the voltage across the dummy load increases, and the pulse duration at the oil elbow inlet and insulator stack regions also slightly increase.

Azimuthal evaluation of formations near borehole: Numerical simulations and field examples

Azimuthal evaluation of formation properties near borehole is an important research direction of well logging technology, and we develop an innovative 3D sonic logging tool for that purpose. Except conventional measurements of monopole and dipole, this tool is added into an azimuthal transmitter station and a set of azimuthal receiver stations, all of which consist of eight piezoelectric vibrators in circumference to excite or acquire sonic waves. Our numerical simulation results show it can detect the heterogeneity of formations by using the measurement mode of azimuthal transmission and azimuthal reception that two types of P-wave with different velocities are found in the waveforms from some azimuths, but only one P-wave exists in other azimuths. Even two types of S-waves in one waveform are discovered when the formations are very hard. Similar phenomena for both P- and S-waves are also observed in field examples.

Azimuthal Transmission Lines for Inductive Voltage Adders With Four PFLs Driving Simultaneously or Separately

In this paper, an inductive cell driven by four pulse forming lines (PFLs), capable of operating at two modes to create a single pulse or four separate pulses, is proposed. A single hardware configuration of azimuthal lines must meet the different requirements of the two operating modes. The optimizations and tradeoffs of azimuthal lines for these two modes are presented. Four candidate azimuthal line configurations that are compatible with either mode are proposed. The cell output voltage and azimuthal uniformity of feed currents are simulated, respectively. The simulation results indicate that the cylinder azimuthal line with four equidistant tabs connected to the cathode palates is the most suitable configuration. As the input pulses are 1000 kV and 25-ns rise time, at the mode with four PFLs driving simultaneously, the cell would produce a pulse with a peak of 865 kV and a rise time of 46 ns into 1.5-Ω load. Meanwhile, it could create four separate pulses of 980 kV and 32-ns rise time into 5-Ω load with each PFL driving separately. In this case, the azimuthally asymmetric coefficient is calculated to be 25.6%. In addition, the voltage of undriven ports, i.e., the voltage applied across the separating switches, is estimated to be about 1150 kV.

Optimized Design of Azimuthal Transmission Lines for the Cell Driven by Two PFLs in Induction Voltage Adders

In this paper, a full-size 3-D electromagnetic model (without electrons) and an equivalent circuit model of a single cell in magnetically insulated induction voltage adders has been established. The simulation results of these two models agree well with each other. On the basis of these two models, azimuthal transmission lines for a cell driven by two pulse forming lines (PFLs) have been optimized. The optimization process aims at matching the impedance to the feed PFLs, ensuring uniform potential distribution along the insulator-stack, maximizing the symmetric current flow around the bore, and minimizing the waveform distortion of the injected pulse. A formula is presented to estimate the azimuthal impedance and an asymmetric coefficient is also defined to quantify the asymmetric extent of the feed pulses. The profiles of the total four candidate azimuthal lines have been simulated and analyzed. The simulation results indicate a relatively low feed asymmetry for all the four profiles. However, considering the waveform quality of the cell output voltage, the azimuthal line profiles with four points connected or wholly connected to the cathode plate are the most suitable for induction cells with two PFL feeding. And the corresponding coefficients $\delta$ are 3.1% and 7.6%, respectively. It is concluded that, when optimizing azimuthal lines for cells with two PFL feeding, the principal consideration should be matching the impedance instead of symmetrizing the current flow.

Transmission of an object azimuth on distance with the help of magnetooptical modulator

This work is devoted to development and analysis of optoelectric method of an object azimuthal location transmission on distance with the help of magnetooptical modulator.

Design of a radiographic integrated test stand (RITS) based on a voltage adder, to drive a diode immersed in a high magnetic field

Recent experiments have adapted existing magnetically insulated induction voltage adders (Sabre, Hermes III) to drive a 10-MV diode immersed in magnetic fields as high as 50 T. In such a diode, an electron beam of tens of kiloamperes can be confined by the magnetic field to a diameter of about 1 mm, and when it strikes a high-Z anode, it can create a bremsstrahlung X-ray source intense enough to radiograph massive objects with high resolution. The radiographic integrated test stand (RITS) is an adder system designed specially to drive such diodes, and it will be used to develop and exploit them. As in other adder-based pulsers, such as Sabre, Hermes III, and Kalif-Helia, the induction cells have amorphous-iron cores, and the pulse-forming system consists of water dielectric pulselines and self-closing water switches that are pulse-charged from Marx-charged intermediate water capacitors through laser-triggered Rimfire switches. An oil prepulse switch in series with each pulseline is designed to reduce cathode prepulse to less than /spl plusmn/5 kV, and a means is provided to bias the cathode and avoid negative prepulse entirely. The RITS pulse-forming system consists of two modules. Each module has one Marx that charges two 3-MV intermediate stores, each of which charges three 7.8 /spl Omega/ pulselines, making six pulselines per module. The two modules in concert can supply 1.35-MV, 50-ns pulses to a 12-cell adder and thus drive a 16-MV diode with a single pulse. The 1,35-MV induction cells each have a single-point feed, from which a single, slotted azimuthal oil transmission line distributes energy uniformly around the cell. The modules can also be pulsed separately at different times, either to power two 8-MV adders that each drive one of two closely spaced cathodes immersed in a common magnetic field or to provide two separate pulses to a common six-cell adder and a single 8-MV diode; in these two-pulse modes, the spacing of the two 50-ns pulses may be chosen to be anything from a few hundred nanoseconds upward. The use of only one pulseline per cell has been shown to increase the extent to which the cell voltages can vary with the timing of closure of the water switches. This and all other functions of RITS have been simulated in detail, and a conservative electrical design has been developed. This will be illustrated, along with the conceptual design of a pulse sorting network that can couple two pulselines efficiently to one cell when the two RITS modules drive a common adder in two-pulse mode.