High Power Test Research Articles

The beam commissioning of a CW high charge state heavy ion RFQ

The SSC-LINAC project is launched at Institute of Modern Physics in China to develop one new linear accelerator (LINAC) injector for separated sector cyclotron (SSC). It includes a high charge state ion source, a CW RFQ and a DTL section, and is designed to accelerate ions up to 580keV/u. Now the ion source and the RFQ cavity have been installed in the main hall and the beam commissioning has been carried out. Two kinds of ions have been tested, 16O5+ and 40Ar8+. The experiment result of 16O5+ is: the measured beam current is 180μA at entrance of RFQ and 150μA at exit of RFQ. The output energy of 16O5+ is 141.89keV/u. The measured beam current is 210μA at entrance of RFQ and 198μA at exit of RFQ for 40Ar8+. The output energy of 40Ar8+ is 142.78keV/u. The experiment results agree with the design parameters of RFQ very well. This paper presents: the design consideration of beam dynamics, RF and cooling structure design; measurement of the cold model; high power test of RFQ and beam commissioning result.

Analysis of a Switched Impedance Transformer-Type Nonsuperconducting Fault Current Limiter

This paper proposes a nonsuperconducting fault current limiter (NSFCL) topology and control strategy. The switched impedance transformer-type NSFCL topology is optimized to protect against short transients and to work in conjunction with other fuses or circuit breakers, hence has the merits of being simple, low cost, and compact. A prototype has been designed and built for a three-phase 600-V RMS,L-L system. It has been tested in a UL-certified high-power test lab with 5-A normal current and 100-kA potential fault current.

Design and tests of 500 kW RF windows for the ITER LHCD system

In the frame of a R&D effort conducted by CEA towards the design and the qualification of a 5GHz LHCD system for the ITER tokamak, two 5GHz 500kW/5s windows have been designed, manufactured and tested at high power in collaboration with the National Fusion Research Institute (NFRI). The window design rely on a symmetrical pill-box concept with a cylindrical beryllium oxide ceramic brazed on an actively water cooled copper skirt. The ceramic RF properties have been measured on a test sample to get realistic values for guiding the design. Low power measurements of the manufactured windows show return losses below −32dB and insertion losses between −0.01dB and −0.05dB, with an optimum frequency shifted toward lower frequencies. High power tests conducted at NFRI show unexpected total power loss for both windows. The ceramic temperature during RF pulses has been found to reach unexpected high temperature, preventing these windows to be used under CW conditions. A post-mortem RF analysis of samples taken from one window shows that the dielectric properties of the ceramic were not the ones measured on the manufacturer sample, which partly explain the differences with the reference modelling.

High-power test of annular-ring coupled structures for the J-PARC linac energy upgrade

Annular-ring coupled structures (ACSs) will increase the beam energy of the Japan proton accelerator research complex (J-PARC) linac from 181 to 400 MeV to achieve a beam power of 1 MW for a materials and life science experimental facility. The mass production of the ACS cavities commenced in March 2009. Before the installation, all cavities require power testing. High-power testing is essential not only for confirming the cavity’s design performance but also for preventing delays in cavity conditioning schedule. However, the 2011 Tohoku earthquake damaged J-PARC facilities, including the ACS power-test area, and cavity conditioning was interrupted for two years. After the facility’s restoration, two ACS cavities (M01 and M11) were conditioned. They performed 15–20% above the designed accelerating field of 4.2 MV/m. As M01 was initially conditioned six years ago, the most recent conditioning time required for M01 was drastically reduced. From this result, we confirmed that long-term stored ACS cavities purged with nitrogen gas do not produce critical cavity performance issues. During high-power operation of M11, which is a unique cavity equipped with a capacitive iris in a waveguide, no significant increases in the temperature and the discharge rate around the capacitive iris were observed. Even considering beam loss due to residual gas scattering, the vacuum pressure was sufficiently low (4 × 10−6 Pa). More stable operation can be expected following a month-long conditioning process before the beam is commissioned. M11’s conditioning successfully demonstrated an auto-conditioning program, and we established the conditioning scheme using this auto-conditioning program for all ACS cavities in a limited time and with limited manpower.

S-band accelerating structures for the PAL-XFEL

One hundred seventy-two accelerating structures are required for the Pohang Accelerator Laboratory X-ray free-electron laser’s (PAL-XFEL’s) 10-GeV main linear accelerator. So far, we have purchased 80 structures from Mitsubishi Heavy Industry (MHI), which have quasi-symmetric couplers in the accelerating structure to reduce the quadruple and the sextuple components of the electric field in the coupling cavity. High-power tests have been conducted for the first structure of the MHI structure, and Research Instruments (RI) has developed a 3-m long accelerating structure that has an operating frequency of 2856 MHz and in/out couplers of quasi-symmetric racetrack shape for the PAL-XFEL linear accelerator. This structure also has been tested by PAL and RI in the Pohang accelerator laboratory (PAL) to check the maximum available electric field gradient. We will describe the test results of these structures and the current status for the fabrication of the other accelerating structures in this paper.

Built-In Self-Test of Transmitter I/Q Mismatch and Nonlinearity Using Self-Mixing Envelope Detector

Built-in self-test (BiST) for transmitters is a desirable choice since it eliminates the reliance on expensive instrumentation to perform radio-frequency signal analysis. Existing on-chip resources, such as power or envelope detectors or small additional circuitry, can be used for BiST purposes. However, due to limited bandwidth, measurement of complex specifications, such as in-phase and quadrature (IQ) imbalance, and third-order intermodulation intercept point (IIP3) is challenging. Since IQ imbalances are most amenable for digital compensation, their characterization and monitoring are desirable. In this paper, we propose a multistep BiST technique for transmitter IQ imbalance and nonlinearity using a self-mixing envelope detector. We derive analytical expressions for the output signal in linear and nonlinear modes. Using linear mode expression, we devise test signals to isolate the effects of gain and phase imbalances, dc offsets, and time skews from other parameters of the system in low-power mode. Once isolated, these parameters are calculated easily with a few mathematical operations. In the next step, using a higher power test signal, the nonlinear behavior of the transmitter is excited and the IIP3 of the transmitter is computed based on the analytical expressions. Simulations and hardware measurements show that the technique can provide accurate characterization of the path.

IMPROVED REFLECTION LOSS PERFORMANCE OF DRIED BANANA LEAVES PYRAMIDAL MICROWAVE ABSORBERS BY COAL FOR APPLICATION IN ANECHOIC CHAMBERS

Agricultural waste is produced at agricultural premises as a result of an agricultural activity. Agriculture residue is made up of organic compounds from the living plants like rice straw, oil palm empty fruit bunch, sugarcane bagasse, coconut shell, banana leaves and others. This research has highlighted their eco-friendly nature and high microwave absorption properties, developing a new and improved form of pyramidal absorbers including high carbon content coal in it. Software simulation is done using CST Microwave studio. Samples are developed using a new technique by adding cobalt as an accelerator, and its performance is analyzed in terms of its reflection loss performance using free space measurement method in the frequency range of 8.2 to 12.4 GHz. This research gives a different definition to microwave absorbers as it is based on environmental and eco- friendly materials unlike commercial absorbers which use polyurethane and polystyrene plastic based materials that pose harm to the surroundings as well as human beings by releasing toxic gases when operating under high temperatures (1). Basic material used is dried banana leaves which comes under the category of agricultural wastes and have a great potential of being used as a good microwave absorber. They are the most essential elements of an anechoic chamber to reduce signal interference. In order to increase the absorption properties of the basic material, finely powdered coal is added due to its high porosity and carbon content. A comparison is shown between banana leaves and banana plus coal as microwave absorbers enhancing the absorption capacity of basic material. The results for these unique types of absorbers are even better than the commercial absorbers. Abandoned agricultural wastes pose a risk to the environmental and public health. While effectively absorbing microwave signals, polyurethane material particulates over time adding contaminants to clean rooms and reducing absorber lifetime. An alternative to these absorbers is found using agricultural wastes like banana leaves, sugarcane bagasse, rice husk etc. for the same purpose. These absorbers are composed of renewable materials and eliminate the toxic gas release problem for polyurethane materials under high power test conditions. They are cost effective materials and can be used to make environment friendly microwave absorbers with desired results. India is the largest producer of the bananas in the world contributing to 28% of world's banana production. Around 20-30% of the by products including banana leaves get wasted every year (9). This waste can be effectively utilized in development of microwave absorbing materials due to presence of high amounts of carbon content (43.5%) in it (2). Macro pores in carbon help in absorption. Table 1 shows weight percentages of different elements in banana leaves.

Development of Resonant Diplexers for high-power ECRH – Status, Applications, Plans

The development of diplexers for ECRH has been pursued at a number of institutes because of their attractive variety of applications: Power combination, non-mechanical, electrically controlled switching (of combined beams) between launchers with tens of kHz, and discrimination of low-power ECE signals from high-power ECRH is feasible. In a first part, this paper reports on plasma experiments with a ring resonator (Mk IIa) at ASDEX Upgrade. Commissioning experiments on fast switching between two launchers for synchronous stabilization of neoclassical tearing modes, as well as in-line ECE measurements have been performed, and experimental issues and first results are discussed. A clear influence of the switching phase on the amplitude of the 3/2 NTM mode was measured, complete stabilization could, however, not be demonstrated yet mainly due to imperfect resonator control. Concepts for improved tracking of the diplexers to the gyrotron frequency are presented. In a second part, the design of diplexers with ring resonators matched to HE11 fields is briefly discussed; these devices can be connected to corrugated waveguides without any mode converters. A compact version (MQ IV) is under investigation, which is compatible with the ITER ECRH system (170 GHz, 63.5 mm waveguide, vacuum tight casing), with the final goal of high-power tests at the 170 GHz gyrotron facility at JAEA in Naka, Japan. First low-power test results are presented.

Improved Efficiency Lens-Loaded Cavity-Backed Transmit Sinuous Antenna

A dual-circular polarized dielectric lens-loaded cavity-backed four-arm sinuous antenna operating in the frequency range from 600 MHz to 2.5 GHz is proposed. The antenna is built without lossy absorber with several design aspects discussed, including substrate/lens loadings, effects of backing, and impedance match to 50 Ω. Fabricated prototype is integrated with a dual-CP beamformer network. The complete configuration is unidirectional, flush-mountable, has input , isolation > 7 dB, boresight realized gain > 3.9 dBic, boresight axial ratio 2.3 dB, and Wobble of Wave (WoW) at the 3-dB elevation cut 2 dB. Through a high power test, the antenna is shown to be capable of transmitting 200 W of CW power with a maximum temperature rise of 60 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C without any external cooling in the operating frequency range. Average overall efficiency of 70% is demonstrated. Two other high-power capable ferrite-tile-backed sinuous antennas are also fabricated to fully showcase unique benefits of the proposed antenna. Presented results should pave the way for the use of sinuous as a transmit antenna in many nontraditional applications requiring higher radiated powers and efficient high-quality dual-polarized patterns over wide frequency ranges.

Reduced Size Planar Dual-Polarized Log-Periodic Antenna for Bidirectional High Power Transmit and Receive Applications

An improved method of more than halving the turn on frequency of a 4-arm log-periodic (LP) antenna for dual-circularly polarized (CP) bidirectional use is demonstrated. The ground plane currents of a slot-LP are manipulated by varying “ground plane” shape to form a ring-turnstile-slot LP aperture and thus extend the overall antenna bandwidth. The proposed concept is used to design and fabricate an antenna that is 2.3 times smaller than the conventional 4-arm LP and works from 500 MHz to 3 GHz. Microstrip impedance transformer/balun is used to feed the LP thus allowing for bidirectional use and much simpler beamforming network for dual-polarized operation. VSWR and far-field behavior of the antenna are characterized and its high-power thermal stability is demonstrated through a high-power test. The advantages over the previously designed ring-turnstile-LP configuration are highlighted and the design principles undertaken to make the antenna high-power capable are illustrated. The prototyped antenna is meant not only to illustrate the proposed concept but also as a viable high-power bidirectional antenna.

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.

India’s largest short circuit generator & its salient features

Short circuit test is one of the very important tests on electrical power equipment to verify its design aspects to withstand the critical severities under the condition of actual fault. To perform these tests a high power source is required. This source can be a grid supply with a high fault level or can be a high power short circuit generator. This paper gives the salient features of high power generator installed at Central Power Research Institute (CPRI), Bangalore. This 2500MVA short circuit generator is of highest capacity in the sub-continent of South Asia as on date. The design features are intricate in nature and complex in terms of stator, rotor damper winding and stator end winding. This paper presents the specification, design concept, constructional features, comparison between salient pole and turbo type of generators and other auxiliaries of the generator. Mechanism of achieving the maximum short circuit current is broadly discussed in this paper. This rare facility at CPRI meets high power testing requirement for the electrical industry and utilities of India and other part of the world. In this paper attempts are also made to bring out the highlights of operational features of capital intensive 2500 MVA SC generator. This generator has been used for short circuit testing of various power system components over the period of time.

Study of Magnetic Shielding Materials and Fabrication of Magnetic Shield for Superconducting Cavities

Magnetic properties of Cryophy were measured at room and cryogenic temperatures using ring samples. Sample-to-sample variation in permeability was evaluated in addition to measurement error. Permeability dependence on the maximum annealing temperature was examined using ring samples annealed at 1100 °C and 1170 °C. From these data, Cryophy was chosen as magnetic shielding material for the superconducting cavities in the main linac section of the cERL (compact Energy Recovery Linac) at KEK. Magnetic properties of Cryophy are presented along with the results of simulation based on the data obtained. The result of the high-power test of the cERL main linac cavities is reported at the end.

The Model of PNGV of High-Power Lithium-Ion Battery and Test Validation

Based on the HPPC test data of 8Ah/144V lithium-ion battery pack, the PNGV model parameters are identified when operation temperature of battery pack is 20°C and the model of PNGV of high-power lithium ion battery pack is build. According to actual operation characteristics of high-power battery pack, the actual output voltage and model predictive voltage are compared under the high-power battery pack different operating condition based on Arbin test bench. It’s showed that the PNGV model predictive precision is not high when high-power battery pack is under steady state condition; the model predictive precision is high when high-power battery pack is under dynamic condition; the difference between model predictive voltage and actual output voltage will be bigger as the operation temperature increased.

High-power test of the new 3-dB power splitter for the PAL XFEL S-band LINAC RF system

The 3-dB power splitter to be used in the Pohang Accelerator Laboratory X-ay Free-electron Laser (PAL XFEL), which have been under construction since 2011, must operate at a peak power of 400 MW and a repetition rate of 120 Hz. For these operational conditions of the PAL XFEL, the old 3-dB power splitter that was originally designed to be used in the PLS LINAC will most suffer from RF breakdown. Therefore, for the new 3-dB power splitter, the original design has been modified to reduce the field gradient and the surface current. The new 3-dB power splitter is designed by using a finite-difference time-domain (FDTD) simulation. We have fabricated a prototype, and the result of a high-power test indicates that the RF performance of the new 3-dB power splitter satisfies the specifications of the PAL XFEL S-band LINAC RF system.

Power Control and Data Acquisition System for High Power Microwave Test Bench

The 6 MW/4.6 GHz lower hybrid current drive (LHCD) system will be set up on the experimental advanced superconducting tokamak (EAST) for achieving a steady-state operation. The high power and continuous wave (CW) mode microwave test bench operating at 250 kW/4.6 GHz has already been finished, which can be used to simulate different kinds of high power microwave environments to test microwave components and units for the new LHCD system. The power control and data acquisition system on the test bench composed of power control, high reflected power protection and data acquisition function is described here in detail. Long-term operation of the test bench showed that the power control and data acquisition system is very stable and reliable.

The development of an optically accessible, high-power combustion test rig

This work summarizes the development of a gas turbine combustion experiment which will allow advanced optical measurements to be made at realistic engine conditions. Facility requirements are addressed, including instrumentation and control needs for remote operation when working with high energy flows. The methodology employed in the design of the optically accessible combustion chamber is elucidated, including window considerations and thermal management of the experimental hardware under extremely high heat loads. Experimental uncertainties are also quantified. The stable operation of the experiment is validated using multiple techniques and the boundary conditions are verified. The successful prediction of operating conditions by the design analysis is documented and preliminary data are shown to demonstrate the capability of the experiment to produce high-fidelity datasets for advanced combustion research.

Development of a magnet power supply with sub-ppm ripple performance for J-PARC with a novel common-mode rejection method with an NPC inverter

The mechanism that generates common-mode noise in inverter circuits, which are widely used in magnet power supplies, was evaluated by a circuit simulation. By following asymmetric operational sequences, pulsed voltage is applied to the parasitic capacitance of power cables that causes a common-mode current at each switching period of the semiconductor switches. Common-mode noise was also found to disturb the normal-mode excitation current by inducing higher frequency components in the applied voltage to the magnet. To eliminate the disturbing effect by the common-mode noise, a newly developed operational method that uses a neutral point clamped, NPC, inverter with reduced switching sequences was evaluated both by a circuit simulation and experimentally. The operational method for the NPC inverter could sufficiently reduce the common-mode noise. A high-power test operation performed using 16 bending magnets at the J-PARC facility achieved a ripple of less than 1ppm in the excitation current.

Coupler conditioning and high power testing of ADS Spoke cavity

Power couplers, used in China-ADS proton linac injector I, are required to transfer 6 kW RF power to the superconducting Spoke cavities. At present, first the two couplers of a coaxial design have been fabricated, which accomplished a high power test at IHEP. The test results indicated that couplers of this design are qualified to deliver 10 kW RF power in continuous travelling wave mode. This paper describes the coupler's room temperature test procedures and results and discusses the original high power test, which was terminated due to serious out-gassing and after some modifications. In the final test, the couplers smoothly exceeded the design power level.

Constant Value Adjusting Method Based on Characteristic Parameters of Process

This paper presents a new method to solve the problem of speed and pressure constant value adjustment in the high-power hydraulic pumps and hydraulic motors performance test system which is based on energy recycling technology. The constant value control method is designed based on characteristic parameters of the process, including control resolution, overshoot and adjustment time. Experiments were implemented to verify the effectiveness of the proposed method. Experimental result shows that the proposed method reduced the test time by about 52.4% than before. The convergence rate of the constant value adjusting process and the test efficiency are significantly improved by the proposed method.