Takayuki Ohmura

A novel laser desorption/ionization method using through hole porous alumina membranes

Rationale A novel matrix‐free laser desorption/ionization method based on porous alumina membranes was developed. The porous alumina membranes have a two‐dimensional (2D) ordered structure consisting of closely aligned straight through holes of sub‐micron in diameter that are amenable to mass production by industrial fabrication processes. Methods Considering a balance between the ion generating efficiency and the mechanical strength of the membranes, the typical values for the hole diameter, open aperture ratio and membrane thickness were set to 200 nm, 50% and 5 μm, respectively. The membranes were coated with platinum on a single side that was exposed to the laser. Evaluation experiments were conducted on the feasibility of this membrane structure for an ionization method using a single peptide and mixed peptides and polyethylene glycol samples and a commercial matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometer in the positive ion mode. Results Results showed a softness of ionization and no sweet spot nature. The capillary action of the through holes with very high aspect ratio enables several loading protocols including sample impregnation from the surface opposite to the laser exposure side. Conclusions The feasibility study indicates that the through hole porous alumina membranes have several advantages in terms of usefulness over the conventional surface‐assisted laser desorption ionization (SALDI) methods. The proposed novel ionization method is termed Desorption Ionization Using Through Hole Alumina Membrane (DIUTHAME).

Detailed performance evaluation of a new 20-inch photomultiplier tube with a Box and Line dynode

Yasuhiro Nishimuraa, Ryosuke Akutsua, Yusuke Sudab, Miao Jiangc, Seiko Hirotac, Daisuke Fukudad , Masahiro Kuzee, Masaki Ishitsukae, Masayuki Nakahataa, Masato Shiozawaa, Yoshinari Hayatoa, Shoei Nakayamaa, Hidekazu Tanakaa, Masashi Yokoyamab, Tsuyoshi Nakayac, Akihiro Minaminoc, Akimichi Taketa f , Yoshihiko Kawaig, Takayuki Ohmurag, Masatoshi Suzukig a Institute for Cosmic Ray Research, University of Tokyo b Department of Physics, University of Tokyo c Department of Physics, Kyoto University d Department of Physics, Okayama University e Department of Physics, Tokyo Institute of Technology f Earthquake Research Institute, University of Tokyo g Hamamatsu Photonics K.K.

Temperature Dependence Measurement of a Hybrid Photo-Detector for Hyper-Kamiokande

1 Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan 2 Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan 3 Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 4 Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan 5 Earthquake Research Institute, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan 6 Hamamatsu Photonics K.K., Hamamatsu, Shizuoka, 430-8587, Japan