Production of a strong slow-positron beam and its application to material sciences

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In recent years, a remarkable progress has been achieved in the techniques for producing slow monochromatic positron beam, with many successful applications to surface physics and ^+-scattering by gas molecules.Under such a new situation, our research group was organized three years ago to construct a strong-beam line for slow positrons using an electron-linac at ETL (Electrotechnical Laboratory, Tsukuba) with an intension to use it widely in material sciences.Before the end of the first fiscal year (starting from April, 1985), Tanigawa and Sueoka, the members of our group, completed a modest beam line at ETL, but it was used only for some preliminary tests for handling slow-positron beams.In the next fiscal year, our initial plan for constructing a positron-beam line at ETL was drastically improved upon receiving a big fund from the Science and Technology Agency, and a new beam line has been constructed by some members of our group(Akahane, Shiotani, and Chiba) in cooperation with the ETL staff. The results of some preliminary tests have ensured them that a strong slow-positron beam of order 10^8/sec or a little higher will be obtained when the linac is operated in the full power. They have succeeded also in stretching the positron beam into a 10msec-pulse by applying, for the first time in the world, a linear-storage system to slow positrons.Besides the ETL-Project, there are a few other projects for constructing slow-positron-beam lines; recently, Ito, Sueoka, Hasegawa and Hyodo of our group succeeded in constructing a beam line at an electron linac in The Japan Atomic Energy Research Institute, and are now trying to improve the luminosity and other characteristics of the beam.It can be concluded that the organization of our research group has really been helpful in activating the Japanese researches with slow positrons, and hence our initial purpose has been successfully accomplished.