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A new horizontal shift bump electromagnet for the J-PARC 3-GeV RCS injection bump system was designed and fabricated. The bump magnet is a pulse magnet that repeatedly excites a trapezoidal waveform of about 1.5 ms duration at 25 Hz. And it is possible to change of the rising and falling time of the pulse waveform with the maximum current of 16 kA and the voltage of 12 kV between 150 and 500 microseconds according to the optimum beam generation condition. In order to design such magnets of such specifications, three-dimensional dynamic magnetic field analysis capable of evaluating eddy currents is required. Using one electromagnet model, comparison of static magnetic field analysis with dynamic magnetic field analysis, and two-dimensional calculations with three-dimensional ones were studied. In addition, we also confirmed the difference between the analysis and measurements as well as the difference of the magnetic field measurement method between the search coil and the Hall probe. We could then have established a pulse electromagnet design method.

The 3-GeV rapid-cycling synchrotron at the Japan Proton Accelerator Research Complex has achieved the high-power beam operation equivalent to 1 MW. As a next step, a study of an upgrade is in progress to mitigate the dose exposure of the maintenance workers in a high residual dose environment and realize the further high intensity beam power. Regarding the upgrade plan's provisions for radiation protection, a new injection scheme has been proposed to make space available for radiation shielding. The total length of the two shift bump magnets of the four magnets is reduced for this purpose, while the other two magnets in the injection straight section remain unchanged. As a result, the two types of pulse magnets are connected separately in series and are excited by two independent power supplies, which are made possible by splitting the presently installed power supply. A structural analysis of the new shift bump magnet is in progress, including simulations of the effects of eddy currents and the coil temperatures by OPERA-3D. This paper describes preliminary results of this analysis and the outlines the modified power supply design.

The present four-terminal kicker at the rapid cycling synchrotron (RCS) at the Japan Proton Accelerator Research Complex has the power-saving benefit that it allows beam extraction by doubling the excitation currents with two shorted ends. In this configuration, two terminals of the kicker are connected to the pulse-forming line while the other two are terminated in a short circuit. On the other hand, beam instabilities are excited in the RCS by the kicker beam impedances, which result from the short-circuit termination of the kicker. In this paper, we describe a scheme to reduce the beam impedance of the kicker using diodes (nonlinear devices), while retaining the benefit of the doubled kicker excitation currents. We employ a simulation technique to determine the beam impedance of the kicker, even when such nonlinear devices and long cables are included. The characteristic of beam impedance measured using the accelerated beams is well explained by that obtained from the simulation.

J-PARC 3-GeV Rapid Cycling Synchrotron (RCS) has two functions: as a proton beam driver to the spallation neutron source at the Material and Life Science Facility (MLF) and also as an injector to the Main Ring (MR). However the required beam parameters for each facility are different. The pulse steering magnet (PSTR) was developed to satisfy these requirements by switching the painting area in each acceleration cycle of MLF and MR and to realize center injection at 400 MeV. Therefore there are two operation modes, painting injection and center injection, for operation of PSTR.

A new power supply for the injection shift bump magnet at the Japan Proton Accelerator Research Complex 3-GeV Rapid Cycling Synchrotron has been designed with the energy upgrading of the linear accelerator to 400 MeV. The power supply is required to output the maximum current of 32 kA, which is 1.6 times the present current. Moreover, peak current ripple noise should be less than ±0.2% of the setting current in a range from 10 kA to 32 kA output current. The insulated gate bipolar transistor chopping system in the present power supply produces the continuous current ripple noise due to the switching, which resonates with the load and excites a forced beam oscillation at about 96 kHz in the injection stage. So, the circuit structure of the new power supply has been changed from the insulated gate bipolar transistor chopping system to the pulse forming network system by switching capacitors. The whole power supply is comprised of 16 banks, each of which outputs 2 kA at 13.2 kV maximum. The first bank has been manufactured and the characteristics were evaluated in the factory. This paper summarizes the design and the preliminary experimental results of the new power supply.

Each pulsed power supply of the bending magnets of the 3-GeV Rapid Cycling Synchrotron injection area at the Japan Proton Accelerator Research Complex has been designed and manufactured for the painting injection in the transverse plane. The magnet currents of both the shift bump magnet and the pulsed steering magnet have a shape of trapezoidal waveform, the flat-top part of which is used for beam injection. The horizontal and vertical painting bump magnets change the beam orbit by using a decaying waveform of the magnet current dynamically. The system with a pulse forming network switching capacitor produces lower current ripples due to the limited number of switchings for the waveform formations. On the other hand, the system of an Insulated Gated Bipolar Transistor chopping system cannot be free from ripple generation due to the continuous switching. However, the Insulated Gated Bipolar Transistor chopping method has an advantage, which produces any shape of required waveform. This paper summarizes the comparison of these power supply systems from view point of the switching noises.

A magnetic switching system replacing thyratron of the kicker magnet power supply in the J-PARC 3 GeV rapid cycling synchrotron (RCS) was studied for stable operation. The core of the magnetic switch is required to have a square B-H loop as an ideal switch. Nano-crystalline alloy (Finemet; FT-1H) was selected for the magnetic core. B-H curves at high magnetization rate (dB/dt) were measured. Magnetization rate dependence of magnetic field and permeability were evaluated based on magnetic domain models. We speculate that the magnetization progress is dominated by the bar-domain mode in the range of magnetization rate we measured. Low leakage current of the magnetic core before saturation flows to the kicker magnets. Closed orbit distortion, , in the RCS caused by the leakage current was evaluated. Calculated results show that the can be suppressed sufficiently. A circuit of the magnetic switching system was designed. A Spice model of the magnetic switching system is described and the simulation results are shown.

JAEA and KEK are jointly constructing a high-intensity proton accelerator project J-PARC. Its main accelerator is a 3-GeV synchrotron. Its injection bump magnets, especially horizontal paint bump magnets, are excited by large pulse currents. Their rated currents are over 10 kA and pulse widths are about 1 ms. Tracking errors are required to be less than 1%. Multiple connected two-quadrant IGBT choppers are adopted for their power supplies. Their output currents are controlled by feedback control with minor loop voltage control (m-AVR). When output current of a chopper intermits at small current, its output voltage rises and current control becomes difficult. In this paper, response of m-AVR and output voltage characteristics at current intermittent region are studied and an improved control scheme is proposed. The performance is confirmed by a test. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 62– 72, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20783

3 GeV RCS (rapid cycling synchrotron) at J-PARC (Japan Proton Accelerator Research Complex) comprises with several magnets of different kinds. These include seven septum magnets for the beam injection and extraction at RCS ring. Design requirements for these magnets often conflicts with efforts to minimize leakage magnetic field. Silicon steel sheets set outside of the septum magnets shield leakage magnetic fields so as to keep proper beam orbits in the ring in most cases. At the beam junction areas for beam injection and extraction, sufficient spacing is not available for installing thick magnetic shields. Vacuum chambers are made by the magnetic stainless steel to reduce the leakage field without a large shield. Results obtained from 3-D field calculations by TOSCA indicate the magnetic leakage field is suppressed down to a few Gauss or less in the present design. All septum magnets and branch structure vacuum chamber made of titanium and magnetic stainless steel are manufactured and assembled successfully. The field measurements of the septum magnets proved that both the strength and also gradient of the magnetic leakage field are diminished.

The J-PARC RCS (rapid cycling synchrotron) is designed to inject the beam from the LINAC, to change their charge from to , to accelerate the beam from 400 MeV to 3 GeV, with protons per pulse at 25 Hz repetition rate, and to extract the beam after the acceleration to the MLF (material and life science experimental facility) and the MR (main ring). Thus the RCS has the beam circulating ring and three beam transport lines. The RCS ring consists of several magnets, and the DC magnets are installed for beam injection and extraction. The four steering magnets and two septum magnets are installed at injection line in order to adjust the beam injection point. One quadratic magnet, two steering magnet and two septum magnets are installed at dump line for the part of the beam with their charge not changed from to at the charge stripping foil. Two deflecting magnets to kick out the beam without exciting the pulse kicker magnets and three septum magnets are installed at the extraction line. Up to now, the DC magnets are developed and manufactured, the field measurements are carried out, and magnets installation into the RCS tunnel are finished. The field distributions of DC magnets are measured by using the new field mapping system with three one-dimensional hall-probes on a 3-axis movable stage. In the case of the quadrupole magnet, the field measurements are not only field mapping but also analyze its magnetic higher order components by the harmonic rotating coil. As a result, the measured field quality meets the design performance requirements of the DC magnets.

Japan Atomic Energy Agency is studying rational manufacturing method and developing the optimum manufacturing technologies of the radial plates used in the toroidal field coils for the International Thermonuclear Experimental Reactor (ITER) in collaboration with the Japanese industries. Three sector form pieces were cut by plasma cutting machine from a hot rolled plate without any difficulties and one of them was machined to a 1.32-m long curved segment of the radial plate having the same size as the actual one. However, unacceptable large deformation about 5 mm flatness, which was not observed in 1-m long straight radial plate, was found after intermediate machining. Since it would be caused by groove direction against the hot rolled direction and/or curved shape of grooves, two trial manufactures of 0.4-m long straight radial plates have been performed to clarify the cause of the large deformation. Detailed investigation showed that the large deformation could be avoided if the groove direction would have been parallel to a rolling direction of the plate. Welding trials by using fiber laser technique was also performed and penetration of 15 mm could be obtained in a welding speed of 0.1 m/min at 5 kW laser power. An optimum manufacturing method has been proposed based on the development of manufacturing technologies.

JAEA and KEK are jointly constructing a high intensity proton accelerator project J-PARC. Its main accelerator is 3GeV synchrotron. Its injection bump magnets, especially horizontal paint bump magnets, are excited by large pulse currents. Their rated currents are over 10kA and pulse widths are about 1ms. Tracking errors are required to be less than 1%. Multiple connected two-quadrant IGBT choppers are adopted for their power supplies. Their output currents are controlled by feedback control with minor loop voltage control (m-AVR). When output current of a chopper intermits at small current, its output voltage rises up and current control becomes difficult. In this paper response of m-AVR and output voltage characteristics at current intermittent region are studied and an improved control scheme is proposed. The performance is confirmed by a test.

The injection bump system of the 3-GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) consists of the pulse bending magnets for the injection bump orbit, which are four horizontal bending magnets (shift bump), four horizontal painting magnets (h-paint bump) and two vertical painting magnets (v-paint bump). The shift bump magnets, which are connected in series in order to form a closed bump orbit. The injection bump system needs the power supplies with the high speed and flexible current pattern. Furthermore, the tracking error is required less than 1.0% for 1.0 mus pulse current. The power supplies with the IGBT (Insulated Gate Bipolar Transistor) chopper units, which are controlled by the switching frequency over 60 kHz, realize its performance. The decay time of the shift bump power supply is less than 200 microseconds

Septum magnets used in the injection and extraction section of the 3 GeV RCS (rapid cycling synchrotron) of J-PARC (Japan proton accelerator research complex) require a large aperture for low-loss operations of high intensity beam, protection against high radiation, and high durability making unnecessary frequent maintenance after high activation. Therefore, the septum magnets have been designed to work in DC for mechanical stability. Also it works outside the beam vacuum, thus eliminating any trouble due to the leakage of cooling water in the vacuum system. A prototype extraction septum magnet was constructed. Magnetic field in the gap of the yoke and leakage field outside of the magnetic shield were measured with a three dimensional Hall probe. The experimental results were compared with three dimensional magnetic field calculations made by TOSCA. The measurement of the magnetic field in the gap agrees well with a simple 3D model. On the other hand, leakage field of the measurement is larger than that of the model. Because the thickness of the return yoke is not sufficient, the magnetic flux density approaches saturation. After we made a more detailed model, it was confirmed that the many bolt holes which fasten the return yoke narrow the effective cross sectional area, thus reduce the effective permeability, and make the magnetic reluctance and the leakage field larger. This paper also describes the results of heat measurements of the magnet and efficiency of water cooling

Kicker magnets in the J-PARC (Japan Proton Accelerator Research Complex) RCS (Rapid Cycling Synchrotron) are being constructed at JAERI (Japan Atomic Energy Research Institute) as the extraction pulse magnet. They kick the accelerated 3 GeV proton beam to the following extraction line at a repetition rate of 25 Hz. The kicker magnet is a distributed-parameter line type in order to obtain a fast rise time of the magnetic field. It is also designed with a large aperture in order to accept a maximum beam power of 1 MW. Therefore, impedance mismatch and fringe fields have a large distorting effect on the flatness of the kicker magnetic field. We examined these effects by simulation and measurement, and contrived to improve the field flatness. In this paper, we present the characteristic features of the RCS kicker systems, describe our magnetic field measurement and improvement, and briefly introduce the field mapping which we are performing now

The injection system of the 3-GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) consists of four main orbit bump magnets (shift bump) to merge the injection beam with the circulating beam. In order to control the injection beam with sufficient accuracy, the shift bump magnets need a wide uniform magnetic field. The magnetic field design and the structural analysis of the shift bump magnets have been performed using three-dimensional electromagnetic and mechanical analysis codes. The shift bump magnets have realized a uniform field with less than 0.35% inhomogeneity over a wider area, which is 400 mm in width and 240 mm in height. Furthermore, the magnets operate with a high magnetic field and they are located in high radioactive level area. The flexible bar is applied to the coil as the countermeasure for thermal expansion and the insulator has strong radiation resistance

Kicker magnets are installed in the extraction section of the RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) facility. They extract a 3 GeV proton beam and inject it into a downstream beam transport line at a repetition rate of 25 Hz. The power supply is mainly composed of the charging unit, the pulse forming network, and thyratrons as switching device. The maximum charging voltage is 80 kV. The kicker magnet is a distributed (transmission line) twin-C type. The circuit parameters are designed to have the 10 Omega characteristic impedance. The magnets are installed in vacuum chambers to prevent voltage breakdown. In order to accept 1 MW beam power, strict conditions are imposed on the kicker system. In the first part of this paper, we give an outline of the RCS extraction kicker system. Next, we report the specifications and performance of the power source and magnet. In addition, we report the measurements of the vacuum performance and magnetic field

Septum magnets are used in the injection and extraction section of the 3 GeV rapid cycling synchrotron (RCS) of J-PARC (Japan Proton Accelerator Research Complex). The RCS needs seven septum magnets, two for the injection line, two for the beam dump line and three for the extraction line, respectively. These septa require a large aperture for low-loss operation with high intensity beams, and high durability for minimizing maintenance after high activation. For insuring mechanical stability the septum magnets have been designed to work DC. The septa magnets work outside a vacuum, thus eliminating any trouble due to the leakage of cooling water into the vacuum system. We have been designing them by using the three dimensional magnet static field calculation code, TOSCA. This paper describes the flatness of the magnetic field in the gap and reduction of the leakage field of the septum magnets in the RCS

The operation of an accelerator at low pressure is an essential requirement to reduce the stripping loss of negative ions, which, in turn, results in high efficiency of the neutral beam systems. For this purpose, a vacuum insulated beam source (VIBS) has been developed at Japan Atomic Energy Research Institute, which reduces the gas pressure in the accelerator by enhanced gas conductance through the accelerator. The VIBS achieves a high voltage insulation of 1 MV by immersing the whole structure of the accelerator in vacuum with a long (~1.8 m) insulation distance. Results of the voltage holding test using a long vacuum gap of 1.8 m indicate that a transition from vacuum discharge to gas discharge occurs at around 0.2 Pa m in the long vacuum gap. So far, the VIBS succeeded in accelerating a 20 mA (H−) beam up to 970 keV for 1 s. It has been demonstrated that the high voltage holding capability of the 1 MV bushing surrounding the VIBS accelerator could be drastically improved by installing new large stress rings that reduces the electric field concentration at the triple junction. After implementing this change, the VIBS sustained 1 MV stably for more than 1200 s. Acceleration of ampere class H− beams at high current density is to be started soon to demonstrate ITER relevant beam optics. The operation of a negative ion source at low pressure is also essential to reduce the stripping loss. However, it was not very easy to attain high current density H− ions at low pressure, since the destruction cross-section of the negative ion becomes large if the electron temperature is >1 eV in low pressure discharge. Using a strong magnetic filter to lower the electron temperature, and introducing higher arc discharge power to compensate for the reduction of plasma density through the filter, an H− ion beam of 310 A m−2 was extracted at a very low pressure of 0.1 Pa. This satisfies the ITER requirement of current density at one-third of the ITER design pressure (0.3 Pa).

The injection performance of the negative-ion based NBI (N-NBI) system for JT-60U has been improved by correcting beamlet deflection and improving spatial uniformity of negative ion production. Beamlet deflection at the peripheral region of the grid segment due to the distorted electric field at the bottom of the extractor has been observed. This was corrected by modifying the surface geometry at the extractor to form a flat electric field. Moreover, beamlet deflection due to beamlet–beamlet repulsion caused by space charge was also compensated for by extruding the edge of the bottom extractor. This resulted in a reduction of the heat loading on the NBI port limiter. As a result of the improvement above, continuous injection of a 2.6 MW H0 beam at 355 keV has been achieved for 10 s. Thus, long pulse injection up to the nominal pulse duration of JT-60U was demonstrated. This has opened up the prospect of long pulse operation of the negative-ion based NBI system for a steady-state tokamak reactor. So far, a maximum injection power of 5.8 MW at 400 keV, with a deuterium beam, and 6.2 MW at 381 keV, with a hydrogen beam, have been achieved in the JT-60U N-NBI. Uniformity of negative ion production was improved by tuning the filament emission current so as to direct more arc power into the region where less negative ion current was extracted.

A vacuum insulated beam source (VIBS), where all the components including the negative ion source and the acceleration grids are immersed in the vacuum, has been designed at Japan Atomic Energy Research Institute. The beam source is characterized by high gas flow conductance that reduces stripping losses of negative ions in the accelerator and improves the acceleration efficiency. The gas flow in VIBS was calculated using a 3-D Monte-Carlo code. At a typical operating pressure of 0.3 Pa in the negative ion source, the stripping loss of D − ions in VIBS is about 23%, which is about half of stripping loss in the gas insulated beam source (GIBS) that was designed in the ITER-FDR design. The acceleration efficiency is improved from 84 to 94%. To enhance the acceleration efficiency further, the possibility for reducing the operating pressure was experimentally studied. It was found the negative ion production in the KAMABOKO source adopted for ITER is dominated by surface production, therefore, the operating pressure can be reduced by improving plasma confinement. It is predicted that the operating pressure in KAMABOKO source can be reduced to 0.15 Pa, where the stripping loss and the acceleration efficiency in VIBS are improved to be 13 and 97%, respectively.

Intense negative ion source producing multimegawatt hydrogen/deuterium negative ion beams has been developed for the neutral beam injector (NBI) in TOKAMAK thermonuclear fusion machines. Negative ions are produced in a cesium seeded multi-cusp plasma generator via volume and surface processes, and accelerated with a multistage electrostatic accelerator. The negative ion source for JT-60U has produced 18.5 A/360 keV (6.7 MW) H− and 14.3 A/380 keV (5.4 MW) D− ion beams at average current densities of 11 mA/cm2 (H−) and 8.5 mA/cm2 (D−). A high energy negative ion source has been developed for the next generation TOKAMAK such as the International Thermonuclear Experimental Reactor (ITER). The source has demonstrated to accelerate negative ions up to 1 MeV, the energy required for ITER. Higher negative ion current density of more than 20 mA/cm2 was obtained in the ITER concept sources. It was confirmed that the consumption rate of cesium is small enough to operate the source for a half year in ITER-NBI without maintenance.

Installation of the kicker magnets in the extraction section of the rapid cycling synchrotron in the J-PARC facility has been completed. They succeeded in extracting the proton beam accelerated up to 3 GeV in the first commissioning with beam. The operation parameters of the kicker system agreed well with the parameters, which were estimated from the magnetic field measurement and the current test of each power supply. The distribution of the integrated magnetic field is flat enough to meet the beam requirements. The beam based measurement of the flattop of the magnetic field was performed with the beam position monitors. Although a ringing structure was observed, which exceeded the specified limit, the degree of the flattop distortion could be corrected by the timing adjustment of the output current. The stability of the power supply is on the order of � 0:2%, which is sufficient to achieve stable beam extraction. The rise time of the output current largely depends on the gas pressure in the thyratrons. Dependence of the rise time on the gas pressure was strictly measured and the number of unwanted prefires could be reduced.

The 3 GeV Rapid Cycling Synchrotron (RCS) at Japan Proton Accelerator Research Complex is nearly at the operational stage with regard to the beam commissioning aspects. Recently, the design painting injection study has been commenced with the aim of high output beam power at the extraction. In order to observe the phase space footprint of the painting injection, a method was developed utilizing a beam position monitor (BPM) in the so-called single pass mode. The turn-by-turn phase space coordinates of the circulating beam directly measured using a pair of BPMs entirely positioned in drift space, and the calculated transfer matrices from the injection point to the pair of BPMs with several successive turns were used together in order to obtain the phase space footprint of the painting injection. There are two such pairs of BPMs placed in two different locations in the RCS, the results from which both agreed and were quite consistent with what was expected.

The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) was commissioned in October 2007, and successfully accomplished 3 GeV acceleration on October 31. Six run cycles through February 2008 were dedicated to commissioning the RCS, for which the initial machine parameter tuning and various underlying beam studies were completed. Then since May 2008 the RCS beam has been delivered to the downstream facilities for their beam commissioning. In this paper we describe beam tuning and study results following our beam commissioning scenario and a beam performance and operational experience obtained in the first commissioning phase through June 2008.

The large-bore magnets in the injection system of a high-intensity proton synchrotron are placed close to each other as compared to their bore sizes. In such cases, the magnetic cores interfere with the fringe fields of adjacent magnets. Moreover, the incoming beam passes through several kinds of time-varying fields along the injection line and the nonlinear field region of the ring quadrupole magnet. The beam behavior under these conditions is analyzed by using the Runge-Kutta method. Although the interference of the magnetic fields does not result in emittance growth, it produces a closed-orbit distortion. Field fluctuations of the time-varying field cause an emittance growth and the nonlinear field deforms the beam profile in phase space of the incoming beam. These effects lead to the modification of the injection scheme. This study focuses on the particle tracking with magnetic field interferences during the early stage of beam commissioning, when the space charge force is not important.

The kicker magnets are installed in the vacuum chamber at the extraction section of the RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex) facility. They kick the 3GeV proton beam to the extraction septum magnets followed by a downstream beam transport line. The RCS is designed to achieve the 1MW beam power with minimum loss. Therefore, the kicker is required to have a wide aperture, UHV (ultra-high vacuum) in its chamber, and uniformity of magnetic field. The wide aperture requires large exciting current and the use environment of the thyratron is very tough. Therefore aging run was found out to be needed. And the uniformity of the magnetic field was improved by changing length of the conductors. In order to achieve the UHV, we succeeded in reducing outgas from components of the magnet. In this paper, we will introduce the specification of the extraction kicker system in the RCS, and report countermeasure against the technical challenge described above.

The construction of J-PARC(Japan proton accelerator research complex) is in a rapid progress, where the first beam commissioning of 3-GeV RCS(rapid cycling synchrotron) is expected to be start on May, 2007. The present work concerns the very final design as well as the calculation of the injection line until the beam dump. This includes an accurate and safe aperture list of all elements in the injection-dump line as well as an accurate estimation of the uncontrolled beam losses so as to optimize them concerning mainly the radiation issues and moreover for the hands-on maintenance.

A processor core, originally designed in a 0.5/spl mu/m Al process, is redesigned for a 0.13/spl mu/m Cu process to create a dual-core processor with 1MB integrated L2 cache, offering an efficient performance to power ratio for compute-dense server applications. Circuit design challenges, including negative bias temperature instability (NBTI), leakage, coupling noise and intra die process variation are discussed.

The J-PARC Project 3-GeV proton synchrotron is designed to accelerate 8.3 /spl times/ 10/sup 13/ protons per pulse at a 25 Hz repetition rate for the injection energy of 400 MeV. The incoming beam emittance of the 400-MeV linac is 4/spl pi/ mm mrad and the acceptance in the 3-GeV synchrotron is 324/spl pi/ mm mrad in both the horizontal and vertical planes. Painting injection system is designed to fit in the FODO structure, which has rather short drift space. The bump orbit for painting injection is designed to have a full acceptance of the circulating orbit through the injection period. A full-acceptance bump orbit will enable both correlated and anti-correlated painting injection.

The simulation model for a new power supply of the injection bump system magnets [1]-[4] of the 3-GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Complex) [5], [6] has been constructed. The new power supply requires the reduction of the ripple noise current which will resonate with load and excites a forced beam oscillation at 96 kHz in the injection stage. In order to incorporate the load impedance in the simulation model, the impedances of a feeder line and the bump magnet with a ceramic vacuum chamber [7] inside were measured. The RF shield is formed on the ceramic surface along the beam direction. The results were successfully analysed using the OPERA-3D [8] and the circuit simulation code, Micro-Cap [9], and showed a good agreement. It was found the RF shield of a ceramic chamber has a resonant structure corresponding to 96 kHz.

Xenon enriched with nonmagnetic isotopes, in which the content of magnetic isotopes is less than 0.4%, has been used as the low temperature matrix for the observation of electronic spin resonance (ESR) spectra of SiH3 radicals and H atoms. The SiH3 radicals were generated by the reaction of SiH4 with H atoms produced by the photolysis of HI. Well resolved proton hyperfine structures, which were smeared out into a broad singlet spectrum when natural xenon was used as the matrix, were observed. The ESR parameters were determined by numerical deconvolution and compared with those obtained for the radicals trapped in other matrices. Simple doublet spectrum of H atoms without superhyperfine structures was also observed after the photolysis of HI at 4.2 K.