Kinomura A, Suzuki R, Oshima N, O'Rourke B E, Nishijima T, Ogawa H
National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan.
Rev Sci Instrum. 2014 Dec;85(12):123110. doi: 10.1063/1.4903754.
A pulsed slow-positron beam generated by an electron linear accelerator was directly used for positron annihilation lifetime spectroscopy without any positron storage devices. A waveform digitizer was introduced to simultaneously capture multiple gamma-ray signals originating from positron annihilation events during a single accelerator pulse. The positron pulse was chopped and bunched with the chopper signals also sent to the waveform digitizer. Time differences between the annihilation gamma-ray and chopper peaks were calculated and accumulated as lifetime spectra in a computer. The developed technique indicated that positron annihilation lifetime spectroscopy can be performed in a 20 μs time window at a pulse repetition rate synchronous with the linear accelerator. Lifetime spectra of a Kapton sheet and a thermally grown SiO2 layer on Si were successfully measured. Synchronization of positron lifetime measurements with pulsed ion irradiation was demonstrated by this technique.
由电子直线加速器产生的脉冲慢正电子束，无需任何正电子存储装置，直接用于正电子湮没寿命谱测量。引入了波形数字化仪，以在单个加速器脉冲期间同时捕获源自正电子湮没事件的多个伽马射线信号。正电子脉冲被斩波并与也发送到波形数字化仪的斩波信号聚束。计算湮没伽马射线与斩波峰值之间的时间差，并在计算机中作为寿命谱进行累积。所开发的技术表明，正电子湮没寿命谱可以在与直线加速器同步的脉冲重复率下，在20微秒的时间窗口内进行。成功测量了聚酰亚胺薄膜和硅上热生长的二氧化硅层的寿命谱。该技术证明了正电子寿命测量与脉冲离子辐照的同步性。
