Precise test of electromagnetic interactions in ortho-positronium spectroscopy

正电子能谱中电磁相互作用的精确测试

• 批准号: 09304034
• 负责人: HIROSE Tachishige
• 金额: $ 23.62万
• 依托单位: Tokyo Metropolitan University (TMU)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09304034/
• 关键词: Positronium; Laser cooling; Doppler shift; Slow positron beam; Thermal positronium; ボーズアインシュタイン凝縮; 陽電子ビーム; バンチャー; 陽電子蓄積; Cr:LiSAFレーザー

1) Production system of positronium (Ps) : We installed a mesh-moderator in the slow ortho-positron (oPs) generator constructed at TMU and were able to increase the intensity of slow oPs by more than one order. A chopper-buncher system created the bunched oPs beam with the time width of 1ns. For achieving efficient collisions of oPs with laser, we have developed a new method of positron accumulation by converting the longitudinal momentum to the transverse one while positron is traveling in magnetic fields. Thermal oPs was efficently produced using a high temperature Mo target heated up to 1000 K and the production rate was measured by means of time-of-flight method.2) Laser system : For the excitation of oPs, we fabricated a Cr : LiSAF laser which provides a long pulse of 200 ns (longer than the oPs lifetime of 142 ns.) having a wave length of 243 nm, sufficiently wide line width to cover the initial Doppler broadening and the repetitio of 25 Hz. The second harmonic and forth harmonic genrators are optimized with respect to the oputput power and the line woidth. We transported the laser to the collision point and made an irradiation test.3) 1S→2P laser excitation : Using Monte Carlo simulation, we examined in detail geometrical condition of laser irradiation, variation of the lifetime owing to the stimulated cooling, mutual relation between laser and positron beams.

1)正电子素（Ps）的产生系统：我们在TMU建造的慢正电子（oPs）发生器中安装了网状慢化剂，并能够将慢oPs的强度提高一个以上的数量级。斩波聚束系统产生了时间宽度为1ns的聚束oPs光束。为了实现oPs与激光的有效碰撞，我们发展了一种新的正电子积累方法，即在正电子在磁场中运动时，将其纵向动量转换为横向动量。采用高温Mo靶加热到1000 K，有效地产生了热oPs，并通过飞行时间法测量了产生速率。2）激光系统：为了激发oPs，我们制造了Cr：LiSAF激光器，其提供了200 ns的长脉冲（比oPs的142 ns寿命长）。具有243 nm的波长、足够宽的线宽以覆盖初始多普勒展宽和25 Hz的重复。对二次谐波和四次谐波发生器的输出功率和线路宽度进行了优化。3）1S→2P激光激发：利用Monte Carlo模拟，详细研究了激光辐照的几何条件、受激冷却引起的寿命变化、激光与正电子束的相互关系。

项目成果

T.kumita et al.: "Development of positronium trap for laser cooling"App.Sur.Sci.. 149. 106-109 (1999)

T.kumita 等人：“用于激光冷却的正电子陷阱的开发”App.Sur.Sci.. 149. 106-109 (1999)

H.Iijima, T.Hirose, 他: "Laser cooling of ortho-Positronium"Nucl. Inst. A Meth Phys. Res. A. (2000)

H.Iijima、T.Hirose 等人：“正正电子的激光冷却”Inst. A Meth Phys A. (2000)

T.Okugi, T.Hirose 他15名: "Evaluation of extremely small horizontal emittance" Phys.Rev.Special Topics. 2. (1999)

T.Okugi、T.Hirose 等 15 人：“极小水平发射度的评估”Phys.Rev.Special Topics 2。（1999）

大森恒彦・広瀬立成: "ソニアーコライダー計画と偏極陽電子ビーム" 日本物理学会誌. 53. 766-774 (1998)

Tsunehiko Omori 和 Tatsunari Hirose：“索尼娅对撞机项目和偏振正电子束”日本物理学会杂志 53. 766-774 (1998)。

H.Iijima 他: "Monte Certo study of ortho-positronium …"Jour.Phys.Soc.Jap.. (To be published). (2001)

H. Iijima 等人：“Monte Certo 研究正正电子......”Jour.Phys.Soc.Jap..（待出版）。