Anode Power Supply Research Articles

Real-Time Feed-backed Anode Power Supply for 170GHz gyrotron in KSTAR

3.6 MW (66 kV/55 A) high voltage power supply system was developed for the 170 GHz ECH&CD system in KSTAR. It consists of the cathode power supply (CPS), anode power supply (APS), and body power supply (BPS). Currently, modulation frequency of APS was limited to less than 1 kHz due to the parasitic capacitance of Zener diode circuit including gyrotron. In order to solve these lacks of controllability and high frequency modulation of APS, the existing APS is replaced by a new type of APS and it is tested for KSTAR 170 GHz gyrotron system. This paper presents the new APS design and characteristics and the test results for 170GHz gyrotron in KSTAR ECH system.

Recent result of gyrotron operation in NIFS

In the last Large Helical Device (LHD) experimental campaign, a 154GHz gyrotron which had been conditioned to generate 1 MW/2 s, 0.5 MW/CW was installed for LHD experiments. Four high power gyrotrons (three-77 GHz/1~1.5 MW and one-154 GHz/1 MW) and a CW gyrotron (84 GHz/0.2 MW) are ready. Our experiment requires high energy and various injection patterns for Electron Cyclotron Resonance Heating (ECRH). Higher individual injection power and various injection patterns, we developed a power enhancement method by stepped anode acceleration voltage control and operated the gyrotron in the hard excitation region. These operations were realized by a remote controlled waveform generator. However the oscillation map of high power or long pulse operation in the hard excitation region were limited because in order to achieve the hard excitation region by the anode voltage control one must pass through the high anode current phase within a time short enough that the anode or the anode power supply is not overloaded. This limitation becomes more critical when the gyrotron beam current is increased in order to increase the output power. In the long pulse operation it was impossible to reach the hard excitation region in a low beam current (<10A).

Development of an 83.2 MHz, Three-Stage RF Amplifier for the SKKUCY-9 Cyclotron

In this paper, we describe the whole process of designing and manufacturing an 83.2 MHz, three-stage radio frequency (RF) amplifier for a SKKUCY-9 cyclotron. It consisted of a preamplifier, intermediate power amplifier (IPA), and power amplifier (PA) stage. The maximum power value for each stage is 0.05 kW, 1.5 kW, then 20 kW RF power. Formula calculation, circuit design, and electromagnetic analysis were implemented in the RF amplifier design. Along with the power stage and anode power supply, an RF amplifier control system for the RF amplifier was developed. After design and manufacturing, we conducted impedance matching measurements with a network analyzer to achieve 50Ω for the IPA and PA. Finally, we analyzed the RF amplifier characteristics by implementing RF testing with both a dummy load and a RF coupler. The expected and measured RF characteristics were in agreement, and a detailed analysis is described.

Development of high voltage power supply for the KSTAR 170 GHz ECH and CD system

A 3.6MW (66kV/55A) DC power supply system was developed for the 170GHz EC H&CD system in KSTAR. The power supply system consists of a cathode power supply (CPS), an anode power supply (APS) and a body power supply (BPS). The cathode power supply is capable of supplying a maximum voltage of −66kV and a current of 55A to the cathode with respect to the collector using pulse step modulation (PSM). The high voltage switching system for the cathode is made by a fast MOS-FET solid-state switch which can turn off the high voltage to the cathode within 3μs in the occurrence of gyrotron faults. The APS is a voltage divider system consisting of a fixed resistor and zener diode units with the capability of 60kV stand-off voltage. The anode voltage with respect to the cathode is controlled in a range of 0–60kV by turning the MOS-FET switches connected in parallel to each zener diode on and off. For high frequency current modulation of the gyrotron, the parallel discharge switch is introduced between the cathode and anode in order to clamp the charged voltage in the stray capacitance. The BPS is a DC power supply with the capability of 50kV/160mA. The nominal operation parameter of BPS was 23kV and 10mA, respectively, and the voltage output is regulated with a stability of 0.025% of the rated voltage. The series MOS-FET solid-state switch is used for on/off modulation in the body voltage sychronizing with anode voltage. The parallel discharge switch is also introduced between the body and collector for high frequency RF modulation. This paper describes the key features of the high voltage power supply system of the KSTAR 170GHz gyrotron as well as the test results of the power supply.

3.6MW Power Supply System of the 170GHz ECH&amp;CD System in KSTAR

A 3.6 MW (-66 kV/55 A) Gyrotron power supply system was developed for the 170 GHz ECH&CD gyrotron system in KSTAR. This power supply system consists of Cathode Power Supply(CPS), Anode Power Supply(APS) and Body Power Supply(BPS). The CPS is using the Pulse Step Modulation by the 32set of IGBT choppers. The respons time of Chopper is very fast. So the cathode voltaget is able to be controlled rapidly. The APS is a sort of voltage devider using zener and switch component. It was achieved 3kHz modulation operation. The BPS is combined the commercial power supply and special high voltage switches. It is very simple topology but 5kHz modulation was accomplished easily. Theses power supply system were installed and commissioned successfully in 2011. This paper presents the topology of the each power supply and test result for 170 GHz gyrotron in KSTAR.

Design and tests of 168-GHz, 500-kW gyrotrons and power supply system

A practical multi-gyrotron oscillation system, using collector-potential depression, composed of six gyrotron tubes and 3 U of power supplies, was designed, fabricated and tested. This system was designed to generate power levels of 3 MW for pulse duration of 1-s at ≈168 GHz for electron cyclotron heating of LHD at the National Institute for Fusion Science. The all-solid-state power supply unit can drive a maximum of three gyrotrons by equipping the collector power supply with three pairs of the anode and body power supplies. The gyrotrons used a TE 31,8,1-mode interaction cavity. A single-stage depressed collector with sweeping coils was employed to increase system efficiency and reduce the heat flux to the collector surface. An internal converter produced a flattened Gaussian profile at a single-disk silicon-nitride window. The output mode was reconverted into the HE 11 mode by an MOU. We reconstructed a main circuit of the power supply unit because of stray capacitors in the actual circuit. There were some differences between the designed and measured output wave profiles. The tubes were tested for 1-s pulse with power levels of 500 kW; system efficiencies were 30% at the peak and 28% at the average and temperatures of the windows were ≈200°C.

Self-adjusting anode power supply for a gyrotron

Sydney University's tunable cw gyrotrons use a simplified power supply arrangement to provide the voltages on the gun electrodes. The cathode supply is conventional, but the anode voltage is provided by a single highvalue resistor connected between the anode and ground. A small fraction of the electrons in the beam are reflected and the anode automatically finds an optimum operating potential. This arrangement is shown to have lower starting currents. Two advantages follow. It becomes easier to operate low-power gyrotrons with modest power supplies and it becomes easier to achieve higher frequencies by exciting harmonics of the electron cyclotron frequency.

Low - Voltage Scanning Electron Microscopy Imaging, Secondary and Backscatter, With Microchannel Plate Detector

The capability to obtain symmetrical images at voltages as low as 200 eV and beam currents less than 9 pico amps is believed to be advantageous for metrology and study of dielectric or biological samples. Symmetrical images should allow more precise and accurate line width measurements than currently achievable by traditional secondary electron detectors. The low voltage and current capability should allow imaging of samples which traditionally have been difficult because of charging or electron beam damage.The detector system consists of a lens mounted dual anode MicroChannel Plate (MCP) detector, vacuum interface, power supplies, and signal conditioning to interface directly to the video card of the SEM. The detector has been miniaturized so that it does not interfere with normal operation of the SEM sample handling and alternate detector operation. Biasing of the detector collection face will either add secondaries to the backscatter signal or reject secondaries yielding only a backscatter image. The dual anode design allows A−B signal processing to provide topological information as well as symmetrical A+B images.Photomicrographs will show some of the system capabilities. Resolution will be documented with gold on carbon. Variation of voltage, beam current, and working distance on dielectric samples such as glass and photoresist will demonstrate effects of common parameter changes.

High Voltage System Design for the IUCF 300 KV Electron Cooling System

A summary of the electron beam high voltage system design for the IUCF Cooler1,2,3, now under construction, is presented. There are extremely stringent regulation requirements (~10ppm) on the main high voltage power supply (-300 kVDC, 15 mA), and less stringent requirements on the gun anode power supply, in order to achieve the regulation needed to store beams in the IUCF Cooler with very low momentum spreads (?p/p ? 2xl0-5). An overview of the main high voltage power supply (HVPS) specifications and design, as well as provisions and plans to improve the regulation are discussed. The electron collection system, modeled after the FNAL collector which was able to collect between 99.9% and 99.99% of the electron beam, is discussed along with the requirements of the associated power supplies. The designs of the high voltage acceleration structures and high voltage platform are discussed, as well as practical design considerations based upon experience with the Fermilab 120 keV electron cooling system.

New RF Power System for SuperHILAC

The upgraded rf system for the SuperHILAC is now operational using 9 new tetrode amplifiers. Each amplifier can produce in excess of lMw of 70 Mhz pulsed rf power. Ferrite is used to decouple the screen grid circuit and to absorb parasitic oscillations. This results in a very stable amplifier with reasonable gain. This system uses a common 6 Mw anode power supply and crowbar system. Overall system efficiency has been increased significantly. We project a 3 year payback on the equipment cost, realized from the power savings alone.

RF System for the RCNP Cyclotron

The outline of the RF system for the RCNP cyclotron is described together with the latest developments. With the double pick up detectors, the dee voltage is stabilized within 10-4(P-P)/P on beam loading condition. To ensure the rapid and easy tuning flexibility of MOPA system, an automatic pretuning system has been developed and works satisfactorily. For the tube protection, a fast crowbar is installed in the anode power supply.