[in Japanese]

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  The role of vacuum science in high intensity accelerators is not only to maintain low pressure in beam line but also to deal with many issues. There are a lot of vacuum equipments in accelerators, which are for example beam collimators, beam monitors, kicker magnets, vacuum chambers and similar devices. All phenomena in the beam line are vacuum phenomena. Furthermore, the special circumstance of existence of high intensity beam expands the framework of vacuum science to radioactivity and interaction between the high energy particle and matter. As a result, the vacuum science is related to almost all equipments and phenomena in accelerators. This report aims to cover the importance of the role of vacuum science in the high intensity accelerators through introducing the developments realized in the 3-GeV Rapid Cycling Synchrotron of Japan Proton Accelerator Research Complex. In particular, 1. outgassing reduction of kicker magnets, 2. vacuum chambers with high permeability, 3. vacuum material with low radio activity will be mentioned.

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  The purpose of this review paper is to explain the procedure to measure vacuum pressure quantitatively. This paper also includes following contents, i) concepts of “uncertainty” and “traceability”, ii) obstructions to measure vacuum pressure quantitatively, iii) methods to generate absolute pressure, and iv) practical use of calibration certificate. It is stressed that two points are most important for quantitative measurement of vacuum pressure; to clarify the relation between the pressure indication of a vacuum gauge and absolute pressure, and to evaluate the reliability of the measurement, in other words “uncertainty”, quantitatively.

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  A pumping-down curve of a vacuum chamber often shows a power-law dependence on time, which has been attributed to a distribution of the adsorption energy of molecules on the chamber wall. We have recently derived an analytical formula that directly converts pressure changes as a function of time into the adsorption density of states (ADOS). In the present paper, on the basis of this formula, we analyzed the pumping-down curves reported in literatures to obtain ADOS of water molecules. The ADOS was dependent on the initial exposure pressure of water. The origin of the pressure dependence is discussed.

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  A pure bulk-phase pentacene film is an attractive material because of its high mobility. We prepared bulk-phase pentacene films by increasing the thermal energy of pentacene molecules. In this method, a heated tungsten (W) mesh was set between a pentacene source and a substrate in a vacuum chamber. The thermal energy of pentacene molecules was increased by contact with the heated W mesh in H₂ atmosphere before reaching the substrate. As the mesh temperature increased from room temperature to 1200℃, the intensity ratio of the bulk phase to the thin-film phase increased from 0 to 9.7. Moreover, we determined the structural properties and growth mechanism related to the thermal energy of pentacene molecules on the growth surface, and the effects of atomic hydrogen.

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  Low resistivity transparent conductive coating consisting of AlN/Ag/AlN nano-multilayer film was fabricated using New Magnetic Hollow-Cathode V-type Sputtering Systems.
  The electrical and optical properties of multilayer films have been examined. A minimum sheet resistance of less than 10 Ohm/sq. and a maximum transmittance of >90% were obtained for AlN (40 nm)/Ag (10 nm)/AlN (40 nm) on Polyethylene terephthalate substrate.

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  During fabrication of Ta₂O₅ solid-electrolyte thin films by radical-assisted sputtering, it was found that a radical-source (RS) treatment involving oxygen-radical irradiation of the Ta₂O₅ thin-film surface for different times enhanced its ECD response characteristics. The Ta₂O₅ films remained amorphous, regardless of the RS treatment time, even though changes were observed in their surface structure and relative density. The ionic conductivity of the films improved substantially due to the RS treatment, and tended to increase with treatment time. FT-IR identified no peak attributable to O-H stretching vibrations with or without the RS treatment, but the intensity of the peak associated with Ta-O stretching vibrations was found to increase with RS treatment time. This indicates that the increase in ionic conductivity was not related to the water content, but was instead the result of effective termination of oxygen defects in the thin film by the highly reactive oxygen radicals, thus enabling unimpeded H⁺ movement.

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