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

近年来，慢正电子单色束的产生技术取得了显著的进展，在表面物理和气体分子的^+散射等方面取得了许多成功的应用，在这种新的形势下，我们于三年前组织了一个研究小组，在ETL的电子直线加速器上建立了慢正电子强束线（筑波电机技术研究所），旨在将其广泛应用于材料科学领域。（从1985年4月开始），我们小组的成员谷川和末冈在ETL完成了一条适度的光束线，但它只用于处理慢正电子束的初步试验。在下一个财政年度，我们在ETL建造正电子束线的初步计划在科学技术厅的大笔资金支持下得到了大幅改善，我们小组的一些成员（Akahane、Shiotani和千叶）与ETL工作人员合作建造了一条新的光束线。一些初步试验的结果已经使他们确信，当直线加速器在全功率下工作时，将获得10^8/秒或稍高量级的强慢正电子束。他们还成功地将正电子束拉伸成10毫秒脉冲，这是世界上第一次应用线性存储系统来减慢正电子。最近，我们小组的Ito、Sueoka、Hasegawa和Hyodo成功地在日本原子能研究所的电子直线加速器上建造了一条束线，可以说，我们这个研究小组的成立，确实有助于启动日本的慢正电子研究，初步的目的已经达到。

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.