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High-sensitivity space-resolved measurements of the number density of neutral free radicals in reactive plasmas have been accomplished by appearance mass spectrometry. This technique is based on several electron volts difference among the appearance potentials for electron-impact ionization. First, some difficulties accompanied with the appearance mass spectrometry are considered, especially on the influence of excited parent molecules and radical sticking. Second, spatial distributions of neutral radical CH3 and CH2 in a parallel plate rf discharge of methane at a pressure of 0.01–0.3 Torr have been measured. The results are well described by a one-dimensional numerical modeling whose input parameters are provided by comprehensive measurements of electron energy distribution, ionic composition, and radical sticking coefficients. Third, the density distributions of CF3 and CF2 radicals in a fluorocarbon etching plasma at a CF4 pressure of 0.01–0.2 Torr have been measured. Finally, several applications of the appearance mass spectrometry to investigations of radical collision processes in gas phase and on solid surfaces are reported, e.g., cross section measurements for electron-impact dissociation of methane into CH3 and CH2 radicals.

The purpose of this paper is to describe an outline of a proton therapy system in Nagoya Proton Therapy Center (NPTC). The NPTC has a synchrotron with a linac injector and three treatment rooms: two rooms are equipped with a gantry and the other one is equipped with a fixed horizontal beamline. One gantry treatment room has a pencil beam scanning treatment delivery nozzle. The other two treatment rooms have a passive scattering treatment delivery nozzle. In the scanning treatment delivery nozzle, an energy absorber and an aperture system to treat head and neck cancer have been equipped. In the passive treatment delivery nozzle, a multi-leaf collimator is equipped. We employ respiratory gating to treat lung and liver cancers for passive irradiation. The proton therapy system passed all acceptance tests. The first patient was treated on February 25, 2013, using passive scattering fixed beams. Respiratory gating is commonly used to treat lung and liver cancers in the passive scattering system. The MLCs are our first choice to limit the irradiation field. The use of the aperture for scanning irradiation reduced the lateral fall off by half or less. The energy absorber and aperture system in scanning delivery is beneficial to treat head and neck cancer.