A Tesla-Blumlein PFL-Bipolar pulsed power generator

A Tesla-Blumlein PFL-Bipolar pulsed power generator, has been successfully designed, manufactured and demonstrated. The compact Tesla transformer that it employs has successfully charged capacitive loads to peak voltages up to 0.6 MV with an overall energy efficiency in excess of 90%. The Tesla driven Blumlein PFL generator is capable of producing a voltage impulse approaching 0.6 MV with a rise time close to 2 ns, generating a peak electrical power of up to 10 GW for 5 ns when connected to a 30 Ω resistive load. Potentially for medical application, a bipolar former has been designed and successfully implemented as an extension to the system and to enable the generation of a sinusoid-like voltage impulse with a peak-to-peak value reaching 650 kV and having a frequency bandwidth beyond 1 GHz. This thesis describes the application of various numerical techniques used to design a successful generator, such as filamentary modelling, electrostatic and transient (PSpice) circuit analysis, and Computer Simulation Technology (CST) simulation. All the major parameters of both the Tesla transformer, the Blumlein pulse forming line and the bipolar former were determined, enabling accurate modelling of the overall unit to be performed. The wide bandwidth and ultrafast embedded sensors used to monitor the dynamic characteristics of the overall system are also presented. Experimental results obtained during this major experimental programme are compared with theoretical predictions and the way ahead towards connecting to an antenna for medical application is considered

Design and operation of a harmonic gyrotron based on a cusp electron gun

Strathclyde theses - ask staff. Thesis no. : T13121This thesis presents the results of successful operation of a 2nd harmonic gyrotron based on a cusp electron gun. The numerical and experimental results agreed well with the gyrotron design parameters. Two gyrotrons based on a cusp electron gun were designed: the first gyrotron operated at the 2nd harmonic and the second gyrotron was studied to look at the scaling of this concept for operation at the 7th harmonic at a frequency of 390 GHz. The cusp electron gun was used to produce the electron beam in the gyrotron which was annular in shape. The electron beam had a voltage of 40 kV, a current of 1.5A and a velocity ratio (perpendicular component to horizontal component) of 1.5. The experimental results from the first cusp electron gun and measurements of the high quality electron beam with ~8% velocity spread and ~10% alpha spread are presented. Analytical, numerical and experimental results of a DC harmonic gyrotron are presented. The 3D PIC code MAGIC was used to simulate the interaction of the harmonic gyrotron such as the TE71 mode at the 7th cyclotron harmonic with the large orbit electron beam with the beam thickness and beam spread introduced into the simulation. The interaction cavity of both gyrotrons was in the form of a smooth cylindrical waveguide. The relationship between the cavity dimensions and cavity Q values has been studied for optimized output at the design mode with the aim of suppressing other competing modes. A linear output taper was designed with low mode conversion at the gyrotron output. A Vector Network Analyzer with high frequency millmetre wave heads was used to measure the millimeter wave properties of the gyrotron cavity. Experiments were conducted using the electron gun for the harmonic gyrotron. The gyrotron and electron gun were built as well as the interlock and safety system, pulsed power supply and magnet, the cooling and vacuum system. Millimetre wave radiation was measured for the 2.6 mm diameter cavity gyrotron operating at the 2nd harmonic at a magnetic field of 2.08 T. Experiments demonstrated that the harmonic gyrotron was sensitive to the magnetic field and electron beam parameters. Millimetre wave radiation from 108GHz to 110GHz was measured with the use of a W-band rectifying crystal detector and high pass cut off filters. The frequency of the measured millimeter wave radiation agreed very well with the design and predictions of theory.This thesis presents the results of successful operation of a 2nd harmonic gyrotron based on a cusp electron gun. The numerical and experimental results agreed well with the gyrotron design parameters. Two gyrotrons based on a cusp electron gun were designed: the first gyrotron operated at the 2nd harmonic and the second gyrotron was studied to look at the scaling of this concept for operation at the 7th harmonic at a frequency of 390 GHz. The cusp electron gun was used to produce the electron beam in the gyrotron which was annular in shape. The electron beam had a voltage of 40 kV, a current of 1.5A and a velocity ratio (perpendicular component to horizontal component) of 1.5. The experimental results from the first cusp electron gun and measurements of the high quality electron beam with ~8% velocity spread and ~10% alpha spread are presented. Analytical, numerical and experimental results of a DC harmonic gyrotron are presented. The 3D PIC code MAGIC was used to simulate the interaction of the harmonic gyrotron such as the TE71 mode at the 7th cyclotron harmonic with the large orbit electron beam with the beam thickness and beam spread introduced into the simulation. The interaction cavity of both gyrotrons was in the form of a smooth cylindrical waveguide. The relationship between the cavity dimensions and cavity Q values has been studied for optimized output at the design mode with the aim of suppressing other competing modes. A linear output taper was designed with low mode conversion at the gyrotron output. A Vector Network Analyzer with high frequency millmetre wave heads was used to measure the millimeter wave properties of the gyrotron cavity. Experiments were conducted using the electron gun for the harmonic gyrotron. The gyrotron and electron gun were built as well as the interlock and safety system, pulsed power supply and magnet, the cooling and vacuum system. Millimetre wave radiation was measured for the 2.6 mm diameter cavity gyrotron operating at the 2nd harmonic at a magnetic field of 2.08 T. Experiments demonstrated that the harmonic gyrotron was sensitive to the magnetic field and electron beam parameters. Millimetre wave radiation from 108GHz to 110GHz was measured with the use of a W-band rectifying crystal detector and high pass cut off filters. The frequency of the measured millimeter wave radiation agreed very well with the design and predictions of theory

The design and development of fast pulsed power supplies using transmission line transformers

This thesis is concerned with the development of Transmission Line Transfomer (TLT) pulsed power supplies and the generation of fast risetime (>50ns), good quality, high repetition-rate voltage pulses for flash x-ray preionisors and other applications. It explains the principle of the TLT and reports on two TLT pulsed power supplies that have been built. The first, or prototype, produced output voltage pulses with risetimes of 50ns and durations of 200ns and was used to power a flash x-ray preionisation source for a mercury bromide laser. The second, a 50kV, 100? device, was built as part of a wider research program concerned with the development of space based pulsed power supplies. The development of ceramic tile technology is also described and the relevant electrical, mechanical and thermal properties of some barium titanate tiles given; it is then shown how ceramic tiles can be used to construct compact pulse generators for TLT systems. Finally, the subject of nonlinear dielectric pulse sharpening is introduced and pulse sharpening in a delay line ladder network containing air-core inductors and non-linear capacitors is demonstrated. It is then explained how these lines can be used to improve the output risetime of a TLT

Investigation of nitrogen lasers for dye laser pumping

The dependence of certain properties of nitrogen lasers on various parameters have been examined and the design of two original nitrogen lasers is presented. The output characteristics of these lasers have been studied as a function of gas pressure, gas flow rate and direction, applied potential, repetition rate, electrode geometry, drive circuitry including the effects of preionization, and the effect of optical feedback by the addition of an optical cavity. The operation of these two lasers in a master oscillator/power amplifier configuration is described and the optimization of this system by varying the drive circuit parameters has been achieved. In the optimized state this configuration produced as much energy per pulse as did the amplifier when operating separately as an oscillator. However, the oscillator/amplifier system produces an output with some additional useful characteristics, such as lower beam divergence and a high degree of polarization. The design of a dye laser which uses a grating at grazing incidence and three mirrors is described. This laser utilizes the polarized output from the oscillator/amplifier system to generate simultaneously two independently tunable wavelengths. A novel pumping arrangement is used which ensures that there is no mode competition between the two wavelengths, that they can have any polarization ratio, that the linewidth of each wavelength can be independently varied and allows the two wavelengths to be generated in different dyes.<p

모드 변환된 상대론적인 후방파 발진기

학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부 물리학전공, 2013. 8. 박건식.Relativistic electron device is a device which generates high power electromagnetic radiation using relativistic electron beam. In our study, the electromagnetic pulse wave (0.5GW-10GHz for 30ns) is normally radiated by using relativistic backward wave oscillator (RBWO) in mildly relativistic regime under 500kV-5kA from relativistic electron device with pulsed magnet system (Max. 3.4Tesla) to focus on relativistic electron beam. Relativistic backward-wave oscillator (RBWO) with relativistic electron beam is capable of producing high-power coherent Cerenkov radiation in the centimeter and millimeter wavelength regimes. The RBWO is designed, fabricated and tested to be operated at 10GHz-Max. 0.5GW level. High power electromagnetic (HPEM) source such as the RBWO has the purpose of transmitting GW-level to specific target. This uses an azimuthally symmetric TM01 waveguide mode for the reason of the characteristic of slow wave structure to interact between relativistic electron beam and backward propagating electromagnetic wave and power capacity to optimize the efficiency. TM01 mode is a doughnut-shaped one with a boresight null due to the cancellation by azimuthally symmetric aperture electric field distribution. In order to focus high-power electromagnetic radiation at the object, it is necessary to be theoretically designed a mode converted antenna which can changes from the TM01 mode to the circularly polarized TE11 mode. The mode converted antenna to be completed on design and fabrication shows that the measured radiation pattern is well matched with the simulated one. In addition, we tested the power estimation of electromagnetic coupling effectiveness on electronic devices at near field range. Relativistic electron device including RBWO, pulsed magnet system and mode converted antenna needs a simultaneously synchronous remote control system with pulsed trigger switch because the discharge and charge characteristic times of respective component devices are different. The remote control system with the software of lab-view is designed, fabricated and tested through several analyses for respective component devices. The study to generate high-power THz radiation source has developed at recent. To increase the frequency of the THz range, some unique physical phenomena with characteristic features including high power THz oversized relativistic backward wave oscillator (RBWO) can be produced. We present an investigation of a coherent Cerenkov radiation (CCR) high power THz source with an oversized slow wave structure of rectangular type. We designed on the cylindrical waveguide structure of a large diameter (D/λ≈8) to generate the power of 0.3GW and to operate at 0.1 THz. The result theoretical design is well matched with the predicted results by a particle-in-cell simulation code, MAGIC 2D with finite difference time domain, CST code.1. Introduction 1.1. Relativistic electron Device 1.2. Relativistic Backward Wave Oscillator (RBWO) 1.3. Issues 1.3.1. Mode conversion antenna 1.3.2. Control system 1.3.3. THz vacuum electronic device (VED) application 1.4. Motivation & Goal 1.5. Outline 1.6. Bibliography 2. Relativistic electron device 2.1. Marx generator 2.1.1. Principle of Marx generator 2.1.2. Test of Marx generator 2.2. Blumlein pulse forming line (PFL) 2.2.1. Principle of Blumlein pulse forming line 2.2.2. Design of Blumlein pulse forming line 2.2.3. Connecting inductor 2.2.4. De-ionized (DI) Water System 2.3. Load 2.3.1. Dummy load 2.3.2. Matching load 2.3.3. The result of load charging and discharging 2.4. Pulsed magnet system 2.4.1. Decision of magnetic field to focus on relativistic e-beam 2.4.2. Design of pulsed magnet power supply 2.4.3. Design of solenoid to generate pulsed magnet field 2.4.4. Magnetic field probe for test 2.4.5. Test of pulsed magnet system 2.5. Design of electron gun 2.5.1. Design of cathode 2.5.2. Design of cathode rod, rod connector and supporter 2.6. Relativistic backward wave oscillator (RBWO) 2.6.1. Design of slow wave structure (SWS) 2.6.2. Resonant reflector 2.6.3. Collector 2.6.4. Simulation for RBWO circuit fabrication 2.6.5. Fabrication of RBWO circuit and cold test 2.7. Bibliography 3. Mode converting antenna 3.1. Design of horn antenna 3.2. Conventional mode converting antenna lens 3.3. Compact design of mode converting antenna lens 3.4. Simulation results for radiation pattern analyses 3.4.1. Conventional mode converting antenna 3.4.2. The flat-plate & convex lens of antenna without mode conversion 3.4.3. The mode converting antenna with three-stepped lens structure and convex lens 3.5. Fabricated mode converting antenna & cold test 3.6. Bibliography 4. Control system 4.1. Synchronous remote control system 4.1.1. Trigger of Marx generator (TMG): triggatron, trigger generator 4.1.2. Adaptor 130 4.1.3. Adaptor test of remote control for Marx generator 4.1.4. Synchronization system for the remote control of relativistic electron device 4.2. Diagnostics 4.2.1. Voltage diagnostic: capacitive voltage probe (CVP) 4.2.2. Current diagnostic in Blumlein PFL 4.2.3. Current diagnostic on the relativistic electron beam 4.2.4. RF coupler to measure RF power from RBWO circuit 4.2.5. RF pick up receiver antenna to measure radiated output RF power 4.2.6. The measurement of the operating frequency 4.3. Integrated mode converted RBWO system 5. Experimental results 5.1. The experimental results of relativistic electron beam 5.2. The experimental results of RF power and the operating frequency from RF measurements system 5.3. The experimental results of radiation pattern by using the mode converting antenna 5.4. Power estimation of electromagnetic coupling effectiveness by mode converted RBWO 5.5. Physical parameter analyses 5.6. Bibliography 6. THz VED application: design of oversized RBWO (0.1THz-0.3GW 30ns) 6.1. Theoretical design of 0.1THz oversized RBWO 6.1.1. Structure and Physical Model 6.1.2. Decision of a Large Diameter in an Oversized Structure 6.1.3. High Current Electron Gun 6.1.4. Dispersion relation and mode selection of slow wave structure under overmoded size 6.1.5. The Resonant Reflector 6.1.6. Collector 6.2. Simulation results 6.2.1. Comparison with basic research of oversized RBWO 6.2.2. Simulation results by PIC simulation (MAGIC 2D code) 6.3. Design of mode converting antenna at 0.1THz 6.4. Bibliography 7. Conclusion Curriculum Vitae Publication List (SCI journals) List of domestic conference papers List of international conference papersDocto

Proof of principle non-invasive pulsed electric field study (measurement and experiments)

Pulsed electric field (PEF) technology applied to food processing was firstly used in the late 1960s. The currently available systems use either conventional Blumlein generators or generators similar to those found in radar power sources to produce the required high voltage pulses. The liquid to be processed is passed through a number of treatment chambers or cells which each contain a pair of electrodes in contact with the liquid. An electric field is thereby applied to the liquid, leading to the technology being termed invasive and it can be used only with liquid food. A novel and non-invasive PEF technology for use in the food processing industry is introduced and investigated in this thesis. The technology represents a novel way of performing PEF treatment. A proof of concept arrangement uses two ceramic cylinders mounted inside the non-invasive PEF cell with a gap of 3 mm between them. A displacement current of the order of mA passes through the non-invasive PEF cell during treatment, as compared with the kA of current usually produced during an invasive treatment. The low current is not only economic in electric energy but also maintains a low food temperature, which implicitly maintains food flavour. In the thesis the electro-optic Kerr effect technique is used to perform accurately the PEF measurement and convincingly prove that strong electric fields are present. Two Kerr water cells were designed and used to determine the Kerr constant for water, since the data presented in the literature is unreliable. The first Kerr water cell uses a pair of Bruce profile stainless steel electrodes and the second a pair of parallel plate stainless steel electrodes. An electro-static solver (Maxwell software) was used to determine the electric field distribution and to calculate the electric field integral to accurately determine the Kerr constant for water. Water samples containing the E-coli bacteria were prepared and filled in the non-invasive PEF cell by the Flavometrix Company. Eight PEF experiments were successfully performed during this research programme and the results show unequivocally that the novel noninvasive technique is effective in significantly reducing the initial concentration of E-coli bacteria. This opens the door for the future design of an industrial prototyp

Solid-State Linear Transformer Driver with Automatic Feedback Control and Its Application to Pulsed Gas Discharge

doctoral thesi