Positronium annihilation in silica aerogel studied by a positron age-momentum correlation technique

中国物理C, 2009, 33(1): 81-84.

^1, , ^2, , ^3, , ^4, , ^5, , ^6, , ^7,

1.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China;Graduate University of Chinese Academy of Sciences,Beijing 100049,China

2.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China;Graduate University of Chinese Academy of Sciences,Beijing 100049,China

3.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

4.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

5.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

6.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

7.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

基金项目: 国家自然科学基金(10575112;10705031;60606011)

Positronium annihilation in silica aerogel studied by a positron age-momentum correlation technique

WANG Dan-Ni ^1, , ZHANG Lan-Zhi ^2, , WANG Bao-Yi ^3, , YU Run-Sheng ^4, , ZHANG Zhi-Ming ^5, , LI Dao-Wu ^6, , WEI Long ^7,

1.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China;Graduate University of Chinese Academy of Sciences,Beijing 100049,China

2.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China;Graduate University of Chinese Academy of Sciences,Beijing 100049,China

3.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

4.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

5.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

6.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

7.Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS,Beijing 100049,China

Keywords： positron age-momentum correlation

A high-performance positron age-momentum correlation (AMOC) spectrometer was newly developed.The counting rate is increased up to 200 cps much larger than the value 20 cps reported by other international groups.And at the same time,the time resolution still keeps at the international level of 220 ps.Furthermore,positronium (Ps) annihilation in silica aerogel was investigated by AMOC,which indicates:(1) Ps annihilation between the grains dominantly undergoes pick-off process and spin conversion from o-Ps to p-Ps;(2) Annealing below 400 ℃ changes the grain surface conditions,i.e.the desorption of hydrogen and the decrease of the defect centers concentration.

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