Search

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.

Background Detection of atrial fibrillation (AF) out of electrocardiograph (ECG) on sinus rhythm (SR) using artificial intelligence (AI) algorithm has been widely studied within recent couple of years. Generally, it is believed that a huge number of ECGs are necessary for developing an AI-enabled ECG to be adequate to correspond to a lot of minor variations of ECGs. For example, structural heart diseases have typical ECG characteristics, but they could be a noise for the purpose of detecting the small signs of electrocardiographic signature of AF. We hypothesized that when patients with structural heart diseases are excluded, AI-enabled ECG for identifying patients with AF can be developed with a small number of ECGs. Methods We developed an AI-enabled ECG using a convolutional neural network to detect the electrocardiographic signature of AF present during normal sinus rhythm (NSR) using a digital, standard 10-second, 12-lead ECGs. We included all patients who newly visited the Cardiovascular Institute with at least one NSR ECG between Feb 1, 2010, and March 31, 2018. We classified patients with at least one ECG with a rhythm of AF as positive for AF (AF label) and others as negative for AF (SR label). We allocated ECGs to the training, internal validation, and testing datasets in a 7:1:2 ratio. We calculated the area under the curve (AUC) of the receiver operating characteristic curve for the internal validation dataset to select a probability threshold, which we applied to the testing dataset. We evaluated model performance on the testing dataset by calculating the AUC and the sensitivity, specificity, F1 score, and accuracy with two-sided 95% confidence intervals (CIs). Results We totally included 19170 patients with 12-lead ECG. After excluding patients with structural heart diseases, 12825 patients with NSR ECGs at the initial visit were identified (1262 were clinically diagnosed as AF anytime during the time course and 11563 were never diagnosed as AF). Of 11563 non-AF patients, 1818 patients who were followed over 1095 days were selected for the analysis with the SR label, to secure the robustness for maintaining SR. Of 1262 AF patients, 251 patients were selected for the analysis with the AF label, of whom a NSR ECG within 31 days before or after the index AF ECG (the first AF ECG during the time course) could be obtained. In the patients with AF label, the NSR ECG of which the date was the nearest to the index AF ECG was selected for the analysis. The AI-enabled ECG showed an AUC of 0.88 (0.84–0.92) with sensitivity 81% (72–88), specificity 80% (77–83), F1 score 50% (43–57), and overall accuracy 80% (78–83). Conclusion An AI-enabled ECG acquired during NSR allowed identification of patients with AF in a small population without structural heart diseases. Funding Acknowledgement Type of funding sources: None.

In rheumatoid arthritis (RA), osteoclastic bone resorption causes structural joint damage as well as periarticular and systemic bone loss. Periarticular bone loss is one of the earliest indices of RA, often preceding the onset of clinical symptoms via largely unknown mechanisms. Excessive osteoclastogenesis induced by receptor activator of NF-κB ligand (RANKL) expressed by synovial fibroblasts causes joint erosion, whereas the role of RANKL expressed by lymphocytes in various types of bone damage has yet to be elucidated. In the bone marrow of arthritic mice, we found an increase in the number of RANKL-expressing plasma cells, which displayed an ability to induce osteoclastogenesis in vitro. Genetic ablation of RANKL in B-lineage cells resulted in amelioration of periarticular bone loss, but not of articular erosion or systemic bone loss, in autoimmune arthritis. We also show conclusive evidence for the critical contribution of synovial fibroblast RANKL to joint erosion in collagen-induced arthritis on the arthritogenic DBA/1J background. This study highlights the importance of plasmacell RANKL in periarticular bone loss in arthritis and provides mechanistic insight into the early manifestation of bone lesion induced by autoimmunity. © 2021 American Society for Clinical Investigation. All rights reserved.

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminium nucleus ($\mu-e$ conversion, $\mu^- N \to e^- N$); a lepton flavor violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90 % upper limit of branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the \mue conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described., Comment: A minor correction applied in Eq. 3

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.

The gut-associated lymphoid tissues (GALTs), including Peyer's patches (PPs), cryptopatches (CPs) and isolated lymphoid follicles (ILFs), establish a host-microbe symbiosis by the promotion of immune reactions against gut microbes. Microfold cell inducer (MCi) cells in GALTs are the recently identified mesenchymal cells that express the cytokine RANKL and initiate bacteria-specific immunoglobulin A (IgA) production via induction of microfold (M) cell differentiation. In the previous study, the Twist2-Cre driver was utilized for gene deletion in mesenchymal cells including MCi cells. In order to investigate MCi cells more extensively, it will be necessary to develop experimental tools in addition to the Twist2-Cre driver mice and characterize such drivers in specificity and efficiency. Here we show that M cell differentiation and IgA production are impaired in the targeted deletion of RANKL by the Col6a1-Cre driver. We compared Col6a1-Cre with Twist2-Cre in terms of the specificity for mesenchymal cells in GALTs. Col6a1-Cre CAG-CAT-EGFP mice exhibited EGFP expression in podoplanin+CD31– cells including MCi cells, while Twist2-Cre mice were shown to target endothelial cells and podoplanin+CD31– cells. Tnfsf11fl/Δ Col6a1-Cre mice exhibited the absence of M cells and severe IgA reduction together with an alteration in gut microbial composition. Moreover, we analyzed germ free mice to test whether changes in the microbiota are the cause of M cell deficiency. M cell differentiation was normal in the CPs/ILFs of germ free mice, indicating that MCi cells induce M cells independently of microbial colonization. This study demonstrates that Col6a1-Cre driver mice are as useful as Twist2-Cre driver mice for functional analyses of GALT-resident mesenchymal cells, including MCi cells. © 2017 Elsevier Inc.

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.

Introduction/Background Patients with complete high cervical spinal cord injury have significantly restricted social participation even with the use of various prosthetic devices. We describe a patient with a C5 complete injury who showed remarkable improvements in social participation after obtaining a service dog. Material and method During March X-8, a 48-year-old man experienced a C5 complete spinal cord injury and underwent anterior cervical fusion. In January X-7, he underwent cystostomy. He discharged from the hospital in September with Zancolli classification: C5A and American Spinal Injury Association Classification: A. Since living with his service dog, he has been giving lectures about his experiences and opinions regarding physical disabilities and barrier-free-concepts at medical institutions and schools. In October X-2, he successfully flew from Ishikawa Prefecture to Tokyo with his service dog. He received the Ishikawa Prefectural Barrier-free Governor Prize. In July X, a semi-structured interview was conducted using the International Classification of Functioning, Disability, and Health (ICF) Rehabilitation Set. The interview and analysis were performed after obtaining written consent. The ethics committee of our institution permitted this study. There are no conflicts of interest. Results Using a service dog positively changed the man's health condition as defined by ICF. The following outcomes were observed: ability to take initiative and focus on actions, increased motivation, clearer planning for specific care needs, physical improvement, increased resilience, increased physical movements, emergence of new roles, better ability to resolve emotional conflict, improved autonomous health management, locomotion with a service dog, communication facilitation, acquisition of stress coping measures, living with consideration of other people, acquiring a job, employment, experiencing positive emotions, reduction of psychological barrier, increased social support and empathy due to visualization of disability, assistance from public service providers ( Fig. 1 ). Conclusion Service dogs can encourage social participation, even for those with a complete high cervical spinal cord injury.

Sao Paulo State Univ UNESP, Ctr Human Reprod Prof Franco Jr, Paulista Ctr Diag Res & Training, Dept Gynecol & Obstet,Botucatu Med Sch, Ribeirao Preto, Brazil

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

The four shift bump magnets (BUHS01-04) of the 3-GeV RCS in J-PARC, which are located at the long straight section, produce a fixed main bump orbit to merge the injection beam into the circulating beam. They are realized with four magnets connected in series to form the accurate closed bump orbit. However, the total integrated magnetic field of the four magnets is not zero because of the magnetic field interference between the shift bump magnet and the adjacent quadrupole magnets (Q magnet). In order to measure the magnetic field distribution accurately, the short search coil and the long search coil were used. Furthermore, the imbalance of the total integrated magnetic field has been improvement by inserting 0.3 mm insulators in the median plane of the return yoke of the BUHS02 and 03. The value of the integration has been decreased from 2358.0 G ldr cm to -71.6 G ldr cm.

Installation of the kicker magnets in the extraction section of the RCS in J-PARC facility was completed. They extract a proton beam accelerated up to 3GeV. Since high voltage of 30 kV, which corresponds to 60 kV for charging the pulse forming line, is applied to the magnet every 40 msec, they are installed in vacuum chambers to prevent the electrical breakdown. However, magnetic field mapping is difficult in vacuum. Therefore, we performed the mapping in the air with applying one third of the operational voltage after checking linear dependence of magnetic field to exciting current. A short search coil on the 3-axis stages was used in the magnetic field mapping. The results showed that the good uniformity was achieved in the whole aperture. The magnetic field distribution of the same type of kicker magnet was in good agreement with each other. The excitation test with the operational charging voltage of 60 kV was also performed in vacuum. At the first stage, we were bothered by the electric breakdown. It was noticed that the reduction of outgassing rate by baking was very effective to suppress the discharge. And the continuous excitation was found to have a conditioning effect for the stable operation.

The beam painting injection system of the 3-GeV RCS in J-PARC, which realizes the uniform beam distributions in the ring, consists of four horizontal paint bump magnets and two vertical paint magnets. The power supply of the paint bump magnet is required to excite the current with high accuracy that varies from 17.6 kA to zero during 0.5 ms. The IGBT chopper units, a switching frequency of which is 50 kHz each, are multiply-connected to achieve the effective carrier frequency of 600 kHz. Accordingly, the output accuracy of the exciting current has been achieved to be less than 1.0%. The measurements of the magnetic field with the actual current waveform were performed and the good performance was confirmed.

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.

New technical issues are initiated in the ITER toroidal field (TF) coil manufacturing because of the scale-up by about 3 times from the TF model coil. The major issues are feasibilities of high accuracy, automatic winding, precise prediction of conductor elongation after heat treatment to insert the conductor in narrow groove of a radial plate, and development of insulation system, which can sustain irradiation of a neutron fluence of 1022 n/m and, in addition, be impregnated in a suitable duration. One of major parts of automatic winding machine, a bending roller head, was developed and trial winding using short sample conductor was successfully carried out. The elongations of the TF conductor after the heat treatment is evaluated to be in plusmn0.03% In addition, results of impregnation test using short samples indicate that it will take about 60 h to impregnate TF coil double-pancake by the method developed in the model coil project. New impregnation technique is under development to shorten the impregnation period.

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.

F-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) scanning has become a critically important tool in diagnosis and management of non-small-cell lung cancer. However, the effectiveness of (18)F-FDG-PET as a diagnostic tool for small-sized lung cancer is controversial. The purpose of this study was to examine the accuracy of( 18)F-FDG-PET in relation to Noguchi's classification in the diagnosis of small peripheral non-small-cell lung cancer.Between January 2003 and April 2006, 150 patients with peripheral lung lesions who were undergoing chest computed tomography (CT),( 18)F-FDG-PET, and operation were analyzed.Eighty-three patients had malignant lesions, and 67 patients had benign lesions. PET had a sensitivity, specificity, positive predictive value, and negative predictive value of 75.9%, 64.1%, 72.4%, and 68.3%, respectively. In 37 patients with peripheral lung cancer measuring 2.0 cm or less in the greatest diameter, the sensitivity was 51.4% and the specificity was 51.9%. Among them, all 4 cases of Noguchi type A adenocarcinoma [localized bronchioloalveolar carcinoma (LBAC)], 4 of 5 type B and 8 of 17 type C were false negative, while 9 of 11 (81.8%) types D, E, and F (invasive carcinomas without a BAC component) were true positive.The accuracy of( 18)F-FDG-PET is generally low in distinguishing malignancy from benign lesions in small lesions (2.0-cm diameter). The significance of PET as a diagnostic tool is small, especially when the tumor has a ground-glass component at a high rate. The sensitivity of PET is high in small invasive carcinomas without a BAC component, but it is difficult to distinguish carcinoma from benign tumor from its image.

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.

Metastasis to a trocar tract (port-site metastasis, PSM) is an uncommon but serious complication that possibly compromises the prognosis of cancer patients treated laparoscopically.A 42-year-old Japanese woman had a 20-cm benign right ovarian cyst resected using gasless lift-laparoscopy. Five years and eight months postoperatively, she noticed a three-cm subcutaneous tumor involving the trocar tract. She was also found to have a pelvic mass and an exploratory laparotomy revealed left ovarian cancer. Based on the histopathological findings, the subcutaneous tumor was diagnosed as a metastasis from the ovarian cancer.This case suggested that PSM could occur without direct or indirect wound contamination during laparoscopic surgery.

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.

Heat loading of acceleration grids has been investigated using a JAERI 400 keV negative hydrogen ion source, which has a three-stage multiaperture accelerator. To investigate the effect of beamlet steering on the heat loading, the apertures in the grounded grid were displaced up to 5 mm. The steering angle increased linearly with the displacement distance of the grid. The obtained steering angle was 7.5 mrad at the displacement distance of 5 mm. It was confirmed that the steering angle agrees well with the thin lens theory. Degradation of beam optics due to the steering was not observed. The heat load of the grounded grid was scarcely changed up to the displacement distance of 2 mm and then increased from 2.5% to 8% of the total input power when the grid was displaced from 2.5 to 5 mm. Heat loads of the other unsteered grids were not changed.