Laser-driven generation of collimated ultra-relativistic positron beams
Laser-driven generation of collimated ultra-relativistic positron beams
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DOI：
10.1088/0741-3335/55/12/124017
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发表时间：
2013-11
影响因子：
2.2
通讯作者：
G. Sarri;W. Schumaker;A. Di Piazza;K. Põder;J. Cole;M. Vargas;D. Doria;S. Kushel;B. Dromey-
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文献类型：
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作者：
G. Sarri;W. Schumaker;A. Di Piazza;K. Põder;J. Cole;M. Vargas;D. Doria;S. Kushel;B. Dromey-
本文报道了利用全光学系统产生准直（发散度为几毫拉德）超相对论正电子束的最新实验结果。正电子束是利用激光加速的超相对论电子束通过高Z固体靶的传播引发的量子电动级联产生的。只要目标厚度与材料的辐射长度相当或小于材料的辐射长度，逃逸正电子束的发散度就与其洛伦兹因子的倒数相当。对于较厚的固体目标，由于级联中基本步骤的数量增加，可以看到发散度逐渐增加，但它仍然保持在几十mrad的数量级，这取决于光束中的光谱分量。这种高度的准直将是进一步注入等离子体尾流场加力燃烧室的基础。
We report on recent experimental results concerning the generation of collimated (divergence of the order of a few mrad) ultra-relativistic positron beams using a fully optical system. The positron beams are generated exploiting a quantum-electrodynamic cascade initiated by the propagation of a laser-accelerated, ultra-relativistic electron beam through high-Z solid targets. As long as the target thickness is comparable to or smaller than the radiation length of the material, the divergence of the escaping positron beam is of the order of the inverse of its Lorentz factor. For thicker solid targets the divergence is seen to gradually increase, due to the increased number of fundamental steps in the cascade, but it is still kept of the order of few tens of mrad, depending on the spectral components in the beam. This high degree of collimation will be fundamental for further injection into plasma-wakefield afterburners.