High-brightness, high-throughput, ultrashort keV and MeV electrons for femtochemistry studies in photoexcited matter

Ultrafast electron diffraction (UED) is the method of choice for studying femtosecond structural dynamics in photoexcited matter [1-5]. Compact keV instruments complement facility-based 8-30 fs MeV sources [6,7] but are constrained by space-charge effects: high-charge operation at 1 kHz limits pulse durations to 150-240 fs [4,5,8], while single-electron modes sacrifice throughput [9]. We present a 90 keV UED platform that overcomes these limitations using RF compression synchronized to the drive laser with <6 fs precision [10], achieving 26–114 fs pulses [11] at 40–100 kHz with direct electron detection, as confirmed by THz electron streaking [12] - combining femtosecond resolution with unprecedented throughput in the keV regime. Using uncompressed electron beams with 300 fs resolution, we have also measured non-thermal dynamics in aluminium [13,14].

Abstract