梦之线光栅单色器温度起伏对能量漂移的影响

为了确保光栅单色器温度起伏引起的能量漂移不影响光束线的表观能量分辨率,建立了单色器高精度的恒温环境。结合上海光源梦之线设计,根据光栅衍射方程推导出单色器温差与能量漂移之间的关系;据此设计了沿光束方向温度起伏较小的单色器恒温环境,测试了温度控制系统不同条件下的长期温度稳定性,并通过长时间多次测量氮气K边吸收谱的方法,得到了相应的能量漂移。结果显示:温度控制系统未启动的情况下,棚屋内最大温度变化约为0.62K,测得的能量漂移约为49 meV;温度控制系统使用独立冷水机时,最大温度变化约为0.20 K,相应的能量漂移约为17meV。实验表明,建立的单色器恒温环境满足设计要求,使得单色器温差引起的能量漂移对梦之线表观能量分辨率的影响得到有效控制。

Effect on energy drift from temperature fluctuation at the Dreamline monochromator

In order to ensure that energy drift from temperature fluctuation of the grating monochromator does not affect apparent energy resolution of the beamline, a high-accuracy constant temperature environment (CTE) was built for the monochromator. Combined with the design of Dreamline beamline at Shanghai Synchrotron Radiation Facility, the relationship between the temperature difference at the monochromator and the energy drift was established by the grating equation. Based on that, the CTE of the monochromator was designed with tiny temperature fluctuations along the beam direction, and long-time temperature stability was tested under different conditions of temperature-controlled system (TCS); then, the corresponding energy drift was obtained through measuring K-edge absorption spectra of nitrogen several times over a long time. The results show that the maximum temperature fluctuation was 0.62 K and the corresponding energy drift was about 49 meV when the TCS was off; in contrast, when it was working with a stand-alone chiller, the maximum temperature fluctuation became 0.20 K and the corresponding energy drift reduced to around 17 meV. The results demonstrated that the built CTE of the monochromator meets the design requirement, and the energy drift from the temperature difference of the monochromator has little effect on the apparent energy resolution of the Dreamline beamline.