Development of high intensity polarized slow positron beam using F-18

Abstract

The utilization of F-18 produced in O-18 enriched water by the O-18(p,n)F-18 reaction, which was to give the highest thick-target saturation activity, has been tried for the purpose of the generation of polarized slow positron beams. The methods of adsorption and evaporation have been tried for the collection and fixation of the F-18 from the O-18 water, and the advantages as well problems to be improved were discussed for the respective methods. As for the adsorption method, various adsorbent substances were tested for the F-18. A strongly basic anion exchange resin was found to be suitable as the adsorbent material, though some thickness of the exchange resin layer was necessary for the efficient collection of F-18. The evaporation method for the collection and fixation of F-18 was thought to be superior to the other methods, and gave 1/10(exp 6) sec slow positron. Five advantages of gas and liquid targets as a positron source were described in comparison with the use of solid targets.

偏極低速陽電子ビームの発生を目的として、最も高い濃縮ターゲット飽和活性を出すO-18(p,n)F-18反応によりO-18濃縮水中に生成するF-18の活用法を試験した。O-18濃縮水からのF-18の収集と固定に吸着法と蒸発法を試験し、それぞれの方法について利点と改善すべき問題を論じた。吸着法については、F-18に適した種々の吸着物質を試験した。強塩基性陰イオン交換樹脂が吸着剤として適していることが分かったが、F-18を効率よく収集するにはある程度の交換樹脂層の厚さが必要である。F-18の収集と固定に用いた蒸発法は1/10(exp 6)sの低速陽電子を発生し他の方法よりも優れていると考える。陽電子源として気体および液体ターゲットを用いた場合の5つの利点を固体ターゲットを用いた場合と比較して記述した。