In this study, we describe an advanced multi-functional, variable-energy positron beam system capable of measuring the energies of multiple "positron-induced" electrons in coincidence with the Doppler-shifted gamma photon resulting from the annihilation of the correlated positron. The measurements were carried out using the unique characteristics of the digital time-of-flight spectrometer and the gamma spectrometer available with the advanced positron beam system. These measurements have resulted in (i) the first digital time-of-flight spectrum of positron annihilation-induced Auger electrons generated using coincident signals from a high-purity Ge detector and a micro-channel plate, (ii) a two-dimensional array of the energy of Doppler-broadened annihilation gamma and the time-of-flight of positron-annihilation induced Auger electrons/secondary electrons measured in coincidence with the annihilation gamma photon, and (iii) the time-of-flight spectra of multiple secondary electrons ejected from a bilayer graphene surface as a result of the impact and/or annihilation of positrons. The novelty of the gamma-electron coincidence spectroscopy has been demonstrated by extracting the Doppler-broadened spectrum of gamma photons emitted due to the annihilation of positrons exclusively with 1s electrons of carbon. The width of the extracted Doppler-broadened gamma spectrum has been found to be consistent with the expected broadening of the annihilation gamma spectrum due to the momentum of the 1s electrons in carbon.

中文翻译：

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用于测量正电子湮灭诱导电子与多普勒频移湮没伽马光子重合的多级飞行时间光谱仪

在这项研究中，我们描述了一种先进的多功能、可变能量正电子束系统，能够测量多个“正电子诱导”电子的能量，同时与相关正电子湮灭产生的多普勒频移伽马光子相吻合。测量是利用数字飞行时间光谱仪和先进正电子束系统可用的伽马光谱仪的独特特性进行的。这些测量产生了 (i) 使用来自高纯度 Ge 探测器和微通道板的重合信号生成的正电子湮灭诱导俄歇电子的第一个数字飞行时间谱，(ii) 多普勒展宽湮灭伽马能量的二维阵列和正电子湮灭诱导俄歇电子/二次电子的飞行时间与湮灭伽马光子同时测量，以及 (iii) 时间-由于正电子的撞击和/或湮灭，从双层石墨烯表面射出的多个二次电子的飞行光谱。伽马电子符合光谱的新颖性已通过提取由于正电子仅与碳的 1s 电子湮灭而发射的伽马光子的多普勒展宽光谱得到证明。由于碳中 1s 电子的动量，已发现提取的多普勒加宽 gamma 谱的宽度与湮灭 gamma 谱的预期展宽一致。