使用谐振微波腔的高质量超快透射电子显微术
High quality ultrafast transmission electron microscopy using resonant microwave cavities
摘要：
通过使用TM $_{110}$偏转腔使连续电子束扫过孔径，可以以高重复率产生超短、低发射度的电子脉冲。这些脉冲可以用于时间分辨电子显微镜，在相对较大的平均电流与原子的空间和时间分辨率。为了证明这一点，在透射电子显微镜中插入了一个空腔，并产生了皮秒脉冲。对于这些脉冲，没有测量到发射度或能量扩展的显著增加。在峰值电流为$814\pm2$ pA时，对于脉冲长度为1.1-1.3 ps的脉冲，电子脉冲的均方根横向归一化发射度在平行于腔的条纹的方向上为$\varepsilon_{n,x}=(2.7\pm0.1)\cdot 10^{-12}$ m rad，在垂直方向上为$\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad。在相同条件下，连续束的发射度为$\varepsilon_{n,x}=\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad。此外，对于脉冲和连续束的半最大能量扩展的全宽度$0.95\pm0.05$ eV已被测量。
英文摘要：
Ultrashort, low-emittance electron pulses can be created at a high repetition rate by using a TM$_{110}$ deflection cavity to sweep a continuous beam across an aperture. These pulses can be used for time-resolved electron microscopy with atomic spatial and temporal resolution at relatively large average currents. In order to demonstrate this, a cavity has been inserted in a transmission electron microscope, and picosecond pulses have been created. No significant increase of either emittance or energy spread has been measured for these pulses. At a peak current of $814\pm2$ pA, the root-mean-square transverse normalized emittance of the electron pulses is $\varepsilon_{n,x}=(2.7\pm0.1)\cdot 10^{-12}$ m rad in the direction parallel to the streak of the cavity, and $\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad in the perpendicular direction for pulses with a pulse length of 1.1-1.3 ps. Under the same conditions, the emittance of the continuous beam is $\varepsilon_{n,x}=\varepsilon_{n,y}=(2.5\pm0.1)\cdot 10^{-12}$ m rad. Furthermore, for both the pulsed and the continuous beam a full width at half maximum energy spread of $0.95\pm0.05$ eV has been measured.
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