IT-8-P-1895 Design of the novel flange-on high lateral and energy resolution ultrashort electron pulse compression system for ultrafast microscopy
An instrumental realization of the idea [1,2] for the ultrashort electron pulse source based on the newly developed imaging energy filter called α-SDA (Spherical Deflector Analyzer) [3] is reported. Its compact design enables the realization of the flange–on instrument concept. It consists of six independent subsystems: photocathode/immersion lens, primary electron column, pass energy tuning element, α-SDA as a central part, focusing/ compression column and detector/target with XY-stage, Fig1. The ultrashort photoelectron bunch created by an attosecond laser pulse propagates through the primary column towards the mirror plane of the α-SDA, where according to simulations, the focusing and temporal reversion occurs [2]. As a consequence, the time-divergent primary electrons at the mirror plane are transformed to a time-convergent pulse at the same plane after 2π deflection. It has been also previously shown, that the aberration free imaging properties of the α-SDA assure a very high lateral (<<1nm) and energy (ΔE/E<10-3) resolution. In the symmetric case with the first time compression exactly at π, the shortest electron pulse behind the α-SDA analyzer is mirror symmetric to the original electron pulse at the photocathode [2]. As a consequence, an extremely dense: ultrashort (<<1fs) and perfectly focused (<<1nm) high energy (104-105 eV) electron bunch strikes the target.
1 K.P. Grzelakowski, US Patent Nr. 7,126,117
2 K. P. Grzelakowski, R. M. Tromp, Ultramicroscopy, 130 (2013) 36
3 K.P. Grzelakowski, Ultramicroscopy 116 (2012) 95
The author acknowledges the financial support by the NCBR (National Centre for Research and Technology) in Warsaw. I would like also to express my gratitude to Dr.Rudolf Tromp for stimulative discussions.
Fig. 1: General outlook of the electron pulse compression system |