Exploring vacuum birefringence based on a 100 PW laser and an x-ray free electron laser beam
Exploring vacuum birefringence based on a 100 PW laser and an x-ray free electron laser beam
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DOI：
10.1088/1361-6587/aaa7fb
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发表时间：
2018-02
影响因子：
2.2
通讯作者：
B. Shen;Z. Bu;Jiancai Xu;Tongjun Xu;L. Ji;Ruxin Li;Zhi‐zhan Xu
中科院分区：
文献类型：
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作者：
B. Shen;Z. Bu;Jiancai Xu;Tongjun Xu;L. Ji;Ruxin Li;Zhi‐zhan Xu
利用上海相干光实验装置的极光站研究了真空双折射现象。强度超过1023 W cm−2的激光脉冲由于超强的电磁场而能够使真空极化。真空折射率沿着电场和磁场方向的细微差别导致光在其中传播时产生双折射效应。真空双折射效应现在可以通过硬X射线自由电子激光（XFEL）光束与高功率激光碰撞来捕获。计算了初始纯线偏振的XFEL光束通过激光激发真空后将获得很小的椭圆率。考虑各种相互作用的几何形状，表明估计的椭圆率位于1.8 × 10 - 10和10 - 9之间的100 PW激光与12.9 keV的XFEL光束相互作用，接近今天的极性检测技术的阈值。设计了详细的实验装置，包括偏振计、聚焦复合折射透镜和光路，在考虑到X射线仪器效率的情况下，我们的设计可以在一次激发中探测到约10个偏振翻转的X射线光子。考虑到背景噪声水平，累积运行是必要的，以获得高置信度的测量。
Exploring vacuum birefringence with the station of extreme light at Shanghai Coherent Light Facility is considered. Laser pulses of intensity beyond 1023 W cm−2 are capable of polarizing the vacuum due to the ultra-strong electro-magnetic fields. The subtle difference of the vacuum refractive indexes along electric and magnetic fields leads to a birefringence effect for lights propagating through. The vacuum birefringence effect can now be captured by colliding a hard x-ray free electron laser (XFEL) beam with a high-power laser. The initial XFEL beam of pure linear polarization is predicated to gain a very small ellipticity after passing through the laser stimulated vacuum. Various interaction geometries are considered, showing that the estimated ellipticity lies between 1.8 × 10−10 and 10−9 for a 100 PW laser interacting with a 12.9 keV XFEL beam, approaching the threshold for todays’ polarity detection technique. The detailed experimental set-up is designed, including the polarimeter, the focusing compound refractive lens and the optical path. When taking into account the efficiencies of the x-ray instruments, it is found that about 10 polarization-flipped x-ray photons can be detected for a single shot for our design. Considering the background noise level, accumulating runs are necessary to obtain high confident measurement.