[en] A versatile heavy-ion accelerator system is under construction at RIKEN which is composed of a cascade of cyclotrons. The ions, from proton to Uranium, are planned to be accelerated up to around 400 MeV/u. As a second phase of the project, MUSES was planned which is composed of an accumulator/cooler ring for RI beam and an electron-RI collider. The available luminosity of collider is dependent upon the production cross-section of RI beam through the projectile fragmentation process, cooling time of RI beams and the intensity limit of electron beam in the electron ring. We investigated the feasibility of experiments to determine the charge distribution in the unstable nuclei. On the other hand, internal target experiments at the accumulator ring will open new and precise physics with use of inverse kinematics. A new scheme of internal target experiments is conceived where a quite thick target is installed and high repetition of beam injection is used from the injector cyclotron. In the present paper, essence of design works of electron-RI collision experiments and accumulator/cooler ring are described emphasizing the role of stochastic and electron cooling, as well as new scheme of internal target operation

[en] Tracer distribution as an index of nutritional support across the thoracic and abdominal aortas in rabbits in the presence or absence of atherosclerotic lesions was evaluated using [¹⁴C]antipyrine, a metabolically inert, diffusible indicator. Intimal plaques were produced by endothelial balloon denudation of the thoracic aorta and a 1% cholesterol diet. After a steady intravenous infusion of 200 microCi of [¹⁴C]antipyrine for 60 seconds, thoracic and abdominal aortas and the heart were excised, and autoradiograms of 20-microns-thick sections were quantified, using microcomputer-aided densitometry. Regional radioactivity and regional diffusional support, as an index of nutritional flow estimated from the timed collections of arterial blood, was 367 and 421 nCi.g-1 (82 and 106 ml.min-1.100 g-1) in thoracic aortic media of the normal and atherosclerotic rabbits, respectively. Radioactivity at the thickened intima was 179 nCi.g-1 (p less than 0.01 versus media). The gruel was noted at a deeper site within the thickened intima, and diffusional support here was 110 nCi.g-1 (p less than 0.01 versus an average radioactivity at the thickened intima). After ligating the intercostal arteries, regional tracer distribution in the media beneath the fibrofatty lesion, but not the plaque-free intima, was reduced to 46%. Thus, in the presence of advanced intimal thickening, the heterogeneous distribution of diffusional flow is prominent across the vessel wall, and abluminal routes are crucial to meet the increased demands of nutritional requirements

[en] A novel tokamak concept with a new type of toroidal field (TF) coils and a central solenoid (CS) whose stress is much reduced to a theoretical limit determined by the virial theorem has been devised. Recently, we had developed a tokamak with force-balanced coils (FBCs) which are multi-pole helical hybrid coils combining TF coils and a CS coil. The combination reduces the net electromagnetic force in the direction of major radius. In this work, we have extended the FBC concept using the virial theorem. High-field coils should accordingly have same averaged principal stresses in all directions, whereas conventional FBC reduces stress in the toroidal direction only. Using a shell model, we have obtained the poloidal rotation number of helical coils which satisfy the uniform stress condition, and named the coil as virial-limited coil (VLC). VLC with circular cross section of aspect ratio A=2 reduces maximum stress to 60% compared with that of TF coils. In order to prove the advantage of VLC concept, we have designed a small VLC tokamak Todoroki-II. The plasma discharge in Todoroki-II will be presented. (author)

[en] A compact injector was designed for an injector of heavy-ion medical accelerators. The injector has two compact linacs, which are a Radio-Frequency-Quadrupole (RFQ) linac and an Interdigital H-mode Drift-Tube-Linac (IH-DTL). We manufactured the RFQ linac and IH-DTL and performed several tests before accelerating C⁴⁺ ion. In this paper, details and results of the tests of these linacs were described. (author)

[en] The magnetic alloy (MA)-loaded RF cavity has been studied for an RF stacking system of the accumulator cooler ring (ACR). RF characteristics of several high-permeability MA cores were measured in the frequency range between 1 and 50 MHz. The effects of the cut-core configuration, cutting the core and leaving air gaps between two circular halves, were also investigated. The results show that the shunt impedance remains high and the appropriate inductance and Q-value can be obtained by increasing the gap width of the cut core in the frequency region of the ACR cavity

[en] We developed the compact injector system for carbon ion radiotherapy. This system consists of the ECR ion source, the Low Energy Beam Transport system (LEBT), the RFQ linac and the Interdigital H-mode DTL (IH-DTL). We manufactured the prototype of the RFQ linac and the IH-DTL and performed the acceleration test. In this test, we have obtained good results to accelerate C⁴⁺ ion up to 4 MeV/u. (author)

[en] A novel tokamak with a new type of toroidal field (TF) coils and a central solenoid (CS) whose stress is much reduced to a theoretical limit determined by the virial theorem is designed and constructed. According to the virial theorem, the best TF coil to produce the strongest magnetic field under the weakest stress requires equal averaged principal stresses in all directions. Therefore, the pitch number of a helical coil is determined to satisfy the uniform stress condition. Moreover, the helical winding is modulated in such a way that poloidal field exists only outside of a torus, because the poloidal field in the torus prevents the breakdown of plasma and causes the torsional force. In the case of the aspect ratio A=2, our optimal coil theoretically increases the magnetic field to 1.4 times larger than the conventional TF coil

[en] A molecular dynamics simulation code using a second-order symplectic integral method is presented. This code is applied to ESR experiments of 1D crystalline beam, and the simulations reproduce the sudden reduction of the momentum spread. Some conditions for obtaining 1D crystalline state are discussed

[en] A DT sub-ignited tokamak reactor is investigated as a transmuter of fission products with an average neutron wall loading of 1 MW m^-2 basing on a novel coil concept to generate strong magnetic fields. By the use of the force-balanced coils (FBC) which reduces the net centering force by a factor of ten from that exerted on toroidal magnetic coils of the same dimension, the steady-state tokamak reactor can be designed to achieve the fusion reaction of Q_DT≅3.7. To transmute the fission product ¹²⁹I effectively, a blanket is designed which consists of the neutron multiplier Be, the tritium breeder Li₂O and a neutron reflector C. Using the optimal blanket, the amount of ¹²⁹I is effectively halved in 2 years with quasi-self-consistent condition, Q_NET≅5.3, local TBR>1.7 and nuclear heating rate in superconducting magnets <1 mW cm^-3. (orig.)

[en] A DT sub-ignited tokamak reactor has been investigated that has an average neutron wall loading of 1 MW/m² and is based on a novel coil concept to generate a strong magnetic field. When the aspect ratio of the coil winding is about 1.7, the forces in the major direction are balanced with the winding pitch of two poloidal rotations round the torus. Thus force balanced coils can be designed which consist of twisted loops in a shape like a figure of eight. Although the coil current has a toroidal component, the poloidal component of the produced magnetic field is made to be negligible inside the winding by modulating the winding pitch. The net centering force is reduced by a factor of 10 from the exerted on toroidal magnetic coils of the same dimension. The authors designed a steady state tokamak reactor with force balanced coils. The fusion reaction of Q_DT approx. = 3.7 is maintained with 58 MW of neutral beam power into a plasma with a major radius of 3.64 m, a minor radius of 0.80 m, an elongation of 1.7, a plasma current of 6.0 MA, an H factor of 2 and a toroidal field on the axis of 8.4 T. (author)