Katsuya Okamura

Development of a Megahertz High-Voltage Switching Pulse Modulator Using a SiC-JFET for an Induction Synchrotron

This paper evaluates the capability of a silicon carbide junction field-effect transistor for an induction synchrotron. The device was operated with a repetition rate of 1 MHz, a drain-source voltage of 1 kV, and a drain current of 50 A in burst mode. Based on the results, the feasibility of continuous-mode operation from the point of view of maximum junction temperature is evaluated. If the total thermal resistance is smaller than 0.7°C/W, the device has potential to be applied in an induction synchrotron.

Novel Package of SiC-JFET for a Switching Pulse Supply Operating at 1 MHz for an Induction Synchrotron

Silicon carbide (SiC) is one of the most promising materials for next-generation power electronic devices, owing to its superior physical properties. Among existing SiC power devices, the SiC junction field-effect transistor (JFET) (SiC-JFET) has excellent performance. A high-power discrete package of a SiC-JFET was developed with the aim of being applied to the High Energy Accelerator Research Organization (KEK) digital accelerator. The device was assembled on a 58 mm × 36 mm copper base plate and with a height of 7 mm. The size of the die was 4.16 mm × 4.16 mm. The device was tested using a pulse discharge circuit and successfully operated at 1 MHz, 1 kV, and 27 A. The power dissipation and the thermal resistance were estimated at 235 W and 0.56 K/W.

Application of the SMES for the Large Scale Accelerator Magnet Power Supply

Power supply for the large-scale accelerator magnets draws a large amount of power from the utility network. For an example, the new proton accelerator complex for high intensity beam (Japan Particle Accelerator Research Complex, J-PARC) is under construction at the Tokai campus of Japan Atomic Energy Agency (JAEA) as a joint project between KEK and JAEA. The J-PARC 50 GeV proton synchrotron (50 GeV-PS) magnets power supplies are constructed with IGBT and IEGT, then the power factor is almost 100%. However, the swing of an active power becomes almost 170 MW, although the average power is about 50 MW. Such large pulse power will give un-allowed disturbances to an ac power line. A SMES system will be required for compensating such as pulse electric power and reducing the disturbances. Case study on circuit configuration of the power supply with SMES and present status of the R&D for the SMES system will be discussed.

Manufacturing and Operation of the Magnetic Septa for the Slow Beam Extraction From the J-PARC 50 GeV Proton Synchrotron

The magnetic septa have been developed for the slow beam extraction from the 50 GeV Proton Synchrotron to the Hadron Experimental Hall at J-PARC (Japan Proton Accelerator Research Complex). The magnetic septa consist of two thin magnetic septa, four medium thick magnetic septa and four thick magnetic septa. The typical operating current is 3000 A and the total kick angle is 77 mrad with the 30 GeV proton beam. All parts of the thin and of the medium thick septum magnets are made of inorganic materials to resist high radiation environment. The positions of the thin and medium thick septa can be aligned remotely in the horizontal range of ±5 mm, which enables us to minimize the beam loss at the magnetic septum section. The septa were installed in the synchrotron ring in December, 2008, after a test at KEK (High Energy Accelerator Research Organization), and were successfully operated in the beam time for the slow beam extraction in January and February, 2009, which resulted in the first 30 GeV slow extracted beam delivery to the Hadron Experimental Hall.

Beam Acceleration Experiment with SiC Based Power Supply and the Next Generation SiC-JFET Package

Utilizing a high power discrete SiC-JFET developed by KEK, a switching power supply (SPS) that had a circuit topology of H-bridge was designed and constructed to drive the induction acceleration system for the KEK digital accelerator. Following the hopeful result with a resistive dummy load, the SPS was installed in the actual KEK Digital Accelerator system. Consequently, heavy ion beam acceleration was successfully demonstrated. Moreover, we have started to develop a next generation package for a high voltage SiC-JFET, which has the voltage rating of 2.4 kV. Two in one module construction, bonding wire free connection, and bidirectional thermal flowing are included in the design concept of the new package.

Novel switching power supply for a digital accelerator

Aiming for applying to future induction synchrotrons, prototype SiC-JFET and SI-Thyrister were tested. Fast switching of SiC-JFET and high-voltage, switching of SI-Thyristor were confirmed.

High frequency power supply with 3.3 kV SiC-MOSFETs for accelerator application

Pulse switching characteristics of newly developed 3.3 kV SiC-MOSFET were investigated and they were provided for a prototype switching power supply (SPS). With supply voltage of 2.5 kV and the load resistor of 100 Ω, rise time Tr and fall time Tf were 76 ns and 88 ns respectively. The SPS exhibited a successful 2.5 kV-20 A-1 MHz burst mode operation.

Super-Bunch Induction Acceleration Scheme in the KEK Digital Accelerator

KEK Digital Accelerator (KEK-DA) [1] is a fast cycling induction synchrotron with induction cells driven by switching power supplies (SPS). The rectangular pulse voltages are precisely controlled by a field-programmable gate array (FPGA). One of our next missions for the KEKDA is to demonstrate super-bunch (very long beam) acceleration technique in which the beam occupies over half of the ring at injection [2]. For that, power supplies for the SPS have to be upgraded from fixed voltage to timevarying voltage to provide beam-required acceleration. This is effective to suppress the blow-up of the longitudinal emittance and ensures the super-bunch acceleration stably.

A Compact Switching Power Supply Utilizing SiC-JFET for an Induction Synchrotron

Utilizing a high power discrete SiC-JFET developed by KEK, a switching power supply (SPS) that had a circuit topology of H-bridge was designed and constructed to drive the induction acceleration system for the KEK digital accelerator. The SPS was operated with a 38 Ω dummy resistance load and bipolar outputs of 800V and 21A were successfully demonstrated at 1 MHz. Also, the combination test with an actual accelerator cell is being conducted.