Time-resolved imaging with HERALDO.

这项提议的目的是发展一种软X射线全息成像技术，用于在GHz区域内对磁化动力学进行时间分辨测量。PI最近通过自相关线性微分算子(Heraldo)首次展示了扩展参考全息术的应用，该全息术用于成像具有高空间分辨率的亚微观磁性元件中的面内和面外磁区。以30 nm的分辨率成像了直径在500 nm以内的坡莫合金薄膜元素的涡旋结构。作为一种无透镜技术，它被证明不受机械摩擦和X射线束漂移的影响，并且是特定于元素的。在这里，我们想扩展这项技术的能力，以研究基于自旋-扭矩传递装置的涡旋振荡器的动态特性。特别是，我们想要探索基于纳米接触元件的自旋扭矩涡旋振荡器(STVO)的回转机制。这里的主要目的是为该技术增加皮秒时间分辨率，以便在旋转周期的不同阶段成像NC STVO的磁化配置。获得的信息将加深对STVO运作的了解，并通过增加多个STVO设备的回转和锁相幅度来提高频率和功率输出。为了实现和应用Heraldo的时间分辨测量，我们建议在同步加速器太阳上进行光束线六分仪的实验。PI最近在这条光束线上获得了18个班次的束流时间，计划于2014年6月运行。六分仪是一种最近开放的光束线，提供高亮度偏振软X射线光束，用于使用弹性和非弹性散射进行测量。作为设备的一部分，六分仪使用傅里叶变换全息术(FTH)为成像提供专用设置。作为一种衍射技术，Heraldo需要与FTH类似的实验装置，因此只需要最小的修改。在实验的第一阶段(2014年6月)，目的是在时间平均模式下测试这项技术，届时将以连续模式测量涡旋构型。在实验的第二阶段，也就是下一轮提案中，目的是在完全时间分辨的模式下应用这项技术。

The aim of this proposal is to develop a soft x-ray hologrphic imaging technique for time-resolved measurements of magnetisation dynamics in the GHz regime. PI has recently demonstrated the first application of Holography with Extended Reference by Autocorrelation Linear Differential Operator (HERALDO) that was used to image both 'in-plane' and 'out-of-plane' magnetised magnetic domains in submicroscopic magnetic elements with high spatial resolution. A vortex structure of permalloy thin film elements with diameters within 500 nm was imaged with a resolution of 30 nm. As a lensless technique it was shown to be immune to mechanical vabration and drift of the x-ray beam, as well as being element specific. Here we would like to extend the capability of this technique for studies of dynamic properties of vortex oscillators based on spin-torque transfer devices. In particular we would like to explore the gyration mechanisms of spin-torque vortex oscillators (STVO) based on nano-contact elements. The main objection here is to add picosecond temporal resolution to the technique in order to image magnetisation configuration of the NC STVO at different phases of the gyration cycle. The information gained will provide increased understanding of the operation of STVOs and lead to increased frequency and increased power output through increased amplitude of gyration and phase-locking of multiple STVO devices. In order to implement and apply the time-resolved measurments by HERALDO we propose to carry out experiments on the beamline SEXTANTS, at the synchrotron SOLEIL. The PI has recently been awarded 18 shifts of beam-time on this beam-line, which is scheduled for operation in June 2014. SEXTANTS is a recently opened beamline offering a high brilliance polarised soft x-ray beam for measurements using elastic and non-elastic scattering. As part of the equipment suit SEXTANTS provides a dedicated set-up for imaging using Fourier Transform Holography (FTH). As a diffraction technique HERALDO require similar experimental arrangements as FTH, thus will require minimum modification. In the first stage of the experiments (June 2014) the aim is to test the technique in time-averaged mode, when the vortex configurations will be measured in a continuous mode. In the second stage of the experiments, in the next round of proposals, the intention is to apply the technique in fully time-resolved mode.