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A singly charged ion source (SCIS) has been designed using a newly developed three-dimensional particle-in-cell (PIC) code. The SCIS is to be used in an isotope separation on-line (ISOL) system that provides 11C ions for heavy-ion cancer therapy with simultaneous verification of the dose distribution using positron emission tomography. The SCIS uses low-energy electron beams to produce singly charged carbon ions efficiently and maintain a high vacuum in the ISOL system. Because the SCIS has to realize a production efficiency of 1% if its carbon ions are to be used in the ISOL system, a suitable design for the SCIS was investigated by using the developed PIC code to study the beam trajectories of the electrons and extracted ions. The simulation results show that hollow electron beams are produced in the designed SCIS resulting in a high effective electron current. The results also predict that the designed SCIS would realize ion-production efficiencies (IPEs) of eSCIS ≃ 6.7% for CO2+ production from CO2 gas and eSCIS ≃ 0.1% for C+ production from CH4 gas. Moreover, to examine the validity of the developed code and confirm that the SCIS was able to be designed appropriately, the space-charge-limited current of the electron gun and the total IPE obtained by adding the IPEs of each ion were compared between the experiment and the simulation.

This study describes measurements on secondary particles produced by a 290 MeV/n Spread Out Bragg Peak (SOBP) carbon beam. Microdosimetric distributions of secondary fragments from the SOBP carbon beam have been measured by using a new tissue equivalent proportional counter (TEPC) system at the Heavy Ion Medical Accelerator in Chiba of the National Institute of Radiological Sciences. The new TEPC system consists of a TEPC, two solid-state detectors (SSD) and a scintillation counter (FSC: forward scintillation counter). The SSDs and FSC can separately identify charged fragments and secondary neutrons produced by the incident carbon ions. Microdosimetric distributions were measured for secondary particles including neutrons produced by a body-simulated phantom consisting of various PMMA plates (thickness: 0, 34.81, 55.2, 60.95, 64.83, 95.03, 114.79, 124.69, 135.2 and 144.98 mm, respectively) to cover the SOBP (at 60-125 mm depth). The new system can separately determine produced fragments from the incident SOBP carbon beam in a body-simulated phantom.

The effects of irradiation of a Nd–Fe–B permanent magnet by fast neutrons was investigated. The decrease in measured magnetic flux density at the center of the magnets were 0.6%, 6.9%, 25.2% and 47.3% after continuous irradiation of 1.1 kGy, 3.7 kGy, 5.6 kGy and 7.4 kGy, respectively. On the other hand, the decrease due to non-continuous irradiation, in which the magnet was first irradiated at 3.7 kGy, then irradiated again at 3.7 kGy nine months later, was 14% smaller than that of continuous irradiation, even for the same total dose. The temperature coefficient of the magnetization did not change with irradiation. Some radioactive materials, such as 147Nd, 151Pm, and 54Mn, were detected in the magnet after irradiation.

The quality of high-temperature superconductors (HTSs) is rapidly increasing, and they can be used in power systems such as SMES systems and in industries as Si single-crystal growth pullers. In the future, HTS conductors are expected to be used for the magnets in nuclear fusion reactors or accelerators. In such applications, HTS conductors will be exposed to radiation. As a result, HTS conductors become radioactive making the operation and maintenance of the reactors or accelerators difficult; this also leads to an increase in the amount of nuclear waste generated. Therefore, we carry out experiments on the radiation damage in HTS conductors to study the characteristics of HTS conductors in radiation environments and to create an industrial database of the radiation effects on HTSs. We also carry out radioactive analyses on HTS conductors in order to clarify the relationship between the irradiation dose and the activity of HTS conductors. In this study, we prepared YBCO and Bi-2223 tapes and carried out the following preliminary experiments: (a) irradiation of the sample HTS tapes with 2-MeV neutrons at room temperature without transport current and (b) study of neutron-induced radioactivity by gamma-ray spectrometry using a Ge detector after the irradiation.

For atomic force microscope (AFM) observations of minute tracks ( ⩽1 μ m) in the CR-39 track detector, an accurate method to measure an extremely small amount of bulk etch is required. A simple method for direct measurements of the bulk etch using AFM was developed. Before the etching, a part of the CR-39 surface was covered with epoxy adhesive resin. The amount of bulk etch was measured as a level difference between the etched surface and the unetched original surface which has been covered with epoxy resin during its chemical etching processing. The details of this method are reported and its limitations are discussed in comparison to a conventional measuring method using tracks of fission fragments.

Fracture Toughness of HIP-sintered silicon nitride decreased with increasing temperature up to 1200°C. The brittle-to-ductile transition was observed in the temperature range from 1200°C to 1275°C: the fracture toughness rapidly increased in the transition region. Above the transition temperature, the fracture toughness decreased with increasing temperature. Fracture toughness of sialon increased with increasing temperature. Transition of fracture mechanism was observed in sialon around 1300°C. The differences of temperature dependence of fracture toughness between two materials are interpreted in terms of the effects of grain-boundary glass phase on fracture.

Strength and fracture toughness tests were carried out on HIP-sintered SiAlON at elevated temperatures. Above 1200°C the strength decreased with increasing temperature. In the temperature range from 1400°C to 1600°C, the strength increased with temperature. On the other hand, the fracture toughness monotonously increased with temperature up to 1400°C. Above 1400°C the fracture toughness gradually decreased with increasing temperature. A stable crack growth region was observed both on the strength specimens and fracture toughness specimens, tested beyond 1200°C. From the detailed observation of the stable crack growth region, β-SiAlON particles were found to be oriented along the tensile direction. Increment of strength and fracture toughness beyond 1400°C may be due to the stable crack growth. The difference in temperature dependence between the strength and fracture toughness may be caused by high- temperature slow crack growth.

Fracture toughness tests were carried out on HIP-sintered silicon nitride at elevated temperatures. The fracture toughness gradually decreased with an increase in temperature up to 1200°C. In the temperature range from 1200°C to 1275°C, a steel-like brittle-to-ductile transition of fracture toughness was observed: the fracture toughness rapidly increased from 4MPa√m to 8MPa√m. Above these temperatures, stable crack growth was observed. From the detailed observation of the stable crack growth region, β-Si3N4 particles were found to be oriented in the tensile direction. The stable crack growth occurred accompanying with bridging and pulling out of β-Si3N4 particles. The transition behavior of fracture toughness results from the transition of fracture mechanism from the stresscontrolled intergranular fracture to the pulling-out of β-Si3N4 particles with shear deformation of intergranular glass phase. The transition temperature was thought to be consistent with the softening point of the intergranular glass phase. The same transition behavior of fracture mechanism was found in the bending strength test.

The fracture toughnesses of Si3N4 (two lots), SiC, TiB2, ZrO2 and Al2O3 were obtained by bending precracked specimens in three different ways: by the bridge compression (BC) method, by fatigue precracking from a crack introduced by the BC method (FP method), and by the controlled surface flaw (CSF) method. For comparison, fracture toughness evaluations by the chevron notch (CN) method and the indentation fracture (IF) method were also carried out. Furthermore, the effect of loading rate on fracture toughness of FP specimens was examined together with a crack propagation test under static fatigue. The KIC values evaluated by FP, CSF and CN methods showed a reasonable agreement with each other for all six of the ceramics tested, while the evaluation by BC and IF methods tended to give considerably lower values than those obtained by the three methods. The normalization of these KIC and KISCC values was done by a theoretical KIC value, which was derived according to the Griffith criterion for unstable fracture. The different fracture modes of these materials were successfully characterized in correlation to the normalized fracture toughness.

A horizontal helical CT system to be used for 3-D treatment planning and for positioning verification of patients in seated position was installed in the treatment room with a fixed horizontal heavy-ion beam line. The system achieved the expected mechanical consistency and reliability.

In the practical application of high-temperature superconductors (HTSs), HTS tapes are frequently exposed to high temperatures during the soldering or epoxy-impregnation process. There is a variety of epoxy resins; high-temperature curing epoxy resin is particularly suitable for superconducting coils because of its high thermal conductivity and low thermal expansion. When applying HTS tapes to magnets, it is necessary to determine the tolerance of the HTS tapes to heat for selecting the epoxy resin. It is also important to gather data on the characteristic changes in the HTS tapes when they are exposed to heat. In this study, we performed experiments to examine the influence of heating on the I- V characteristics of commercially available YBCO and Bi-2223 tapes. We chose temperature and heating duration as experimental parameters. The sample tapes were heated in a thermostatic chamber, and thermocouples were attached to sample tapes to monitor the rise in temperature. We measured the I-V characteristics in liquid nitrogen before and after temperature rise treatment.

Since silicon nitride is hard to sinter, it is general to sinter with small amounts of sintering aids, such as Al2O3 and Y2O3. Therefore, very thin glass phase formed at the grain boundary has an influence on high temperature mechanical properties of sintered silicon nitride. Silicon nitride is one of major candidate materials for potential structural components in high-performance turbine application. In service, components in turbine application may be subjected to loading at elevated temperatures. It is, therefore, essential to gain detailed understanding of fracture behavior at elevated temperatures. From this viewpoint, the characteristics of high temperature strength 1–5 and creep strength 6–9 have been actively investigated lately for silicon nitride in comparison with other ceramic materials. However, the detailed fracture behavior of silicon nitride including the influence of intergranular glass phase at elevated temperatures has not always been obvious.

A configuration for an untuned broadband rf cavity with a low-voltage standing wave ratio (VSWR) is proposed. Although an untuned broadband cavity is currently implemented by loading magnetic alloy (MA) cores, the VSWR of such a cavity is expected to be no less than approximately 2.0 in the operational frequencies sweeping by a factor of about 10. A type of rf cavity, “in-series multistation” cavity, described here can cover a much broader frequency range sweeping by a factor of 20, while keeping the VSWR value below 1.2. The system consists of multiple stations, each of which is loaded with low-Q high-permeability MA cores. A “bench” test circuit was built and successfully tested.

Fracture toughness tests are carried out using three kinds of precracked specimen: (1) a specimen with a fatigue precrack introduced at an elevated temperature in a method proposed by the authors. (2) a specimen with a brittle precrack introduced by the bridge compression (BC) method proposed by Sadahiro et al., and (3) a specimen with a surface precrack introduced by Vickers hardness indentation. Fracture toughness evaluations by the chevron notch method and the indentation fracture method are also carried out. The precracks introduced by the three methods can not be assumed to be ideal cracks under the as-precracked condition. However, if the relevant treatments are made, the precracks are presumed to be ideal cracks, and almost the same fracture toughness values are obtained by using treated precracks. Based on these results, the authors recommend the method of precracking by cyclic fatigue at room temperature at the low ΔKfmax where a precrack introduced by the BC method is used as the starter for fatigue cracking.